What is anesthesia

If you are having surgery, your doctor will give you medicine called an anesthetic. Anesthesia or anaesthesia is a state of temporary induced loss of sensation or awareness. The word anaesthesia is coined from two Greek words: “an” meaning “without” and “aesthesis” meaning “sensation”. Anesthesia may include analgesia (relief from or prevention of pain), paralysis (muscle relaxation), amnesia (loss of memory), or unconsciousness. A patient under the effects of anesthetic drugs is referred to as being anesthetized.

The purpose of anesthesia can be distilled down to three basic goals or end points:

  1. Hypnosis (a temporary loss of consciousness and with it a loss of memory). In a pharmacological context, the word hypnosis usually has this technical meaning, in contrast to its more familiar lay or psychological meaning of an altered state of consciousness not necessarily caused by drugs.
  2. Analgesia (block pain sensation which also blunts autonomic reflexes)
  3. Muscle relaxation

The ideal general anesthetic drug would provide hypnosis, amnesia, analgesia, and muscle relaxation without undesirable changes in blood pressure, pulse or breathing.

Anesthesia enables the painless performance of medical procedures that would cause severe or intolerable pain to an unanesthetized patient.

There are three main types anesthesia, all of which affect the nervous system in some way and can be administered using various methods and different medications 1):

  1. Local anesthesia – numbs one small area of the body. You stay awake and alert.
  2. Regional anesthesia – blocks pain in an area of the body, such an arm or leg. A common type is epidural anesthesia, which is often used during childbirth.
  3. General anesthesia – makes you unconscious. You do not feel any pain, and you do not remember the procedure afterwards.

All three involve the administration of drugs to produce a change in sensation and they are frequently used in combination. Confusion sometimes arises, because the term “ local anaesthesia” is used to refer to what is properly called “ regional anaesthesia”, so that an operation “under local” may in fact be an operation using regional anaesthesia.

You may also get a mild sedative to relax you. You stay awake but may not remember the procedure afterwards. Sedation can be used with or without anesthesia.

The type of anesthesia or sedation you get depends on many factors. They include the procedure you are having and your current health.

Factors that influence the choice of anaesthetic include:

  • The procedure to be performed. Some procedures can only be performed under general anaesthesia. For example, a patient undergoing removal of the gallbladder, whether by means of a laparoscopic or key-hole technique or through a standard incision, needs a general anaesthetic. For other procedures it is reasonable to consider whether or not the operation should be carried out under local, regional or general anaesthesia, or if a combination of techniques should be used, such as combined regional and general anaesthesia. For example, a patient undergoing an examination of the knee using a special instrument called an arthroscope could be offered a choice of local, regional, or general anaesthesia. A patient undergoing an open-heart operation might be offered a combination of general anaesthesia and regional anaesthesia.
  • The experience, expertise and preference of the anaesthetist can vary with different techniques.
  • Your own preference – whether or not you would prefer to be unconscious or wish to remain as conscious and in control as possible. Most patients prefer to be unconscious for major surgical procedures. For some procedures it is increasingly common for patients not to have a general anaesthetic—for example, caesarean section.
  • Age – It is common for children to have a general anaesthetic for procedures that might be done without any form of anaesthetic in an adult, for example, MRI (magnetic resonance imaging) scanning. This is because children may not understand the explanations or be able to lie still.

Do you have a choice?

No matter what operation, examination or other treatment you are to undergo, you may ask your anaesthetist if there is any choice in the anaesthetic method. You should also understand that some surgeons are more comfortable operating on patients who have received one form of anaesthetic rather than another. This most often means that the patient has a general anaesthetic.

The surgeon does not choose the type of anaesthetic you will receive, unless there is no anaesthetist involved in your care. However, the surgeon may discuss the choice with you and with your anaesthetist. In the same way, your anaesthetist does not choose what operation you will have or how it will be carried out. Again, your anaesthetist may discuss your operation with you and your surgeon, particularly if you have special anaesthetic problems.

Meeting your anaesthetist

You may meet your anaesthetist in a preoperative Assessment Clinic. Otherwise, you will meet shortly before you enter the Operating Room. This meeting may take place on a ward, in an admissions unit, or in a holding area outside the Operating Room.

Your anaesthetist will review information contained in your hospital record or chart, such as the results of any tests you have undergone. He or she will ask you some additional questions, such as your, or your relatives’, experience with anaesthetics. Your anaesthetist will talk to you about possible choices of anaesthetic, such as between general and regional or local anaesthesia, and about any specific problems or concerns you have. In addition, your anaesthetist will discuss with you the different choices for postoperative pain management.

After this, your anaesthetist will examine you, by looking at your mouth, your teeth, and the veins of your hands, arms, and neck, and may listen to your chest. If you are to have a regional or local anaesthetic, your anaesthetist may also look at the area of your body where the anaesthetic is to be injected, such as the small of your back.

As the last part of pre-anaesthetic assessment, the anaesthetist makes an overall evaluation of you and assigns a numerical classification. This is known as the ASA Class, where ASA stands for American Society of Anesthesiologists. Although it was developed in the United States, the ASA Class is now used worldwide as a way of classifying patients according to how well or ill they are. This classification refers only to your physical condition at the time of assessment. The higher the score, the less well you are. An ‘E’ after the appropriate classification designates that you are to undergo an emergency operation.

  • ASA Class I: A normal healthy patient
  • ASA Class II: A patient with mild systemic disease
  • ASA Class III: A patient with severe systemic disease limiting activity but not incapacitating
  • ASA Class IV: A patient with incapacitating systemic disease that is a constant threat to life
  • ASA Class V: An extremely ill patient who is not expected to live 24 hours with or without an operation.

The ASA classification is not a score of how risky the anaesthetic might be for you. However, the ASA Class has been shown to correlate with the risk of complications occurring after the operation, particularly the risk of dying. This risk is related to the operation performed and how well or ill a patient was before the procedure (or a patient’s preoperative physical condition). In general, there is very little contribution from the anaesthetic to the chance of a patient dying after a procedure.


There are types of medications which you might be asked NOT to take before your anaesthetic – some antidepressants, anticoagulants including aspirin, and diabetic drugs.

Antidepressants – monoamine oxidase inhibitors or MAOIs

There is a specific class of drugs used to treat depression, known as monoamine oxidase inhibitors or MAOIs. There is a probability of a serious drug interaction between the MAOI drug and adrenaline (epinephrine) or pethidine ( meperidine), producing an over-excitation of the brain and a potentially fatal rise in blood pressure. (The same reaction can occur if you are taking an MAOI drug and eat mouldy cheese or drink red wine.) If you are taking this type of drug and you need to have an anaesthetic, then you and your doctor or psychiatrist should arrange for the drug to be stopped before your anaesthetic. However, if you need to have an emergency operation or have not stopped taking the drug, tell your anaesthetist so he or she can avoid giving you any of the drugs which may interact.

Anticoagulants and aspirin

These drugs are used to thin the blood and reduce clotting. If you are taking warfarin or coumadin, then you must check with both your anaesthetist and surgeon for specific instructions on when and how to taper the dose of these drugs. If you have had a stroke or been threatened with one, you may be taking a type of drug known as an anti-platelet agent, or one of the non-steroidal anti-inflammatory drugs such as aspirin. You may also be taking aspirin because of heart problems or arthritis. Again, you should check with your anaesthetist and surgeon. These drugs have an effect on how certain cells in the blood stream (platelets) stick to each other when blood clots. Because the cells are no longer so sticky, there can be more bleeding during and after operations. The effects of these drugs on blood clotting may last for as long as 14 days. Some patients can stop taking these drugs without any problems before anaesthesia and surgery. However, other patients should not stop them, including those with very bad heart disease or a past stroke. Also, patients who rely on these drugs for relief of pain and other symptoms from their arthritis may find that their joints are much more painful if they stop the tablets. Again, it is vital that you ask the doctor who normally looks after you, as well as your anaesthetist and surgeon.

Diabetic drugs and insulin

If you normally take tablets for the control of blood sugar for diabetes, you should not do so on the day you are to have your anaesthetic. If you do so and then go without eating (fasting), your blood sugar might drop very low while you are under the anaesthetic, when you cannot complain of the symptoms of low blood sugar or hypoglycemia. In addition, one of these drugs, metformin, has been associated with the development of a severe condition where acid builds up in the blood stream. The probability of this developing is more likely in patients who undergo certain procedures, such as heart operations where the heart-lung machine is used.

On the other hand, if you are taking insulin for control of diabetes, you will want to discuss how best to manage your insulin. Ideally, patients with diabetes should be scheduled to undergo their procedures as the first case of the day. This will allow them more time during the day to recover and perhaps be able to start back on a reasonably normal diet. Some diabetics will be asked to take less than their normal dose of insulin. A few diabetics might even omit taking any insulin until the procedure is over and they are capable of eating or drinking again. All diabetic patients should have their blood sugar tested immediately before the operation and again when they arrive in the recovery room. Some patients also have their blood sugar tested during the procedure by their anaesthetist.


Anaesthetists recommend that you do not have anything alcoholic to drink on the day before and the day of the operation. In general, patients who drink alcohol every day need higher doses of anaesthetic drugs than those patients who do not consume any alcohol. So it is also important to tell your anaesthetist exactly how much alcohol you drink and how often.

Herbal and OTC medications

Many patients now take herbal and other ‘over the counter’ (OTC) medications and supplements. Some of these medications may interact with anaesthetic drugs, as well as those used to relieve pain in the postoperative period. For example, St. John’s Wort is a herbal preparation commonly used by patients who are feeling ‘blue’ or a little depressed. This herb is known to affect the length of time that certain prescription drugs last, as well as some anaesthetic agents.

Other non-prescription items of importance are antacids, such as Mylanta, Maalox, or Pepto-Bismul. These antacids come either as a thick creamy liquid or as tablets. You should not take any of these after the midnight before your operation. If inhaled into your lungs, these antacids can cause damage from the tiny particles from which they are made.

You should therefore give your anaesthetist a complete list of every herbal, vitamin, and supplement you are taking, in addition to your prescription medications. Some anaesthetists actually prefer that you bring to the hospital or clinic all of the medications, herbals, supplements and vitamins that you actually take, even if it means bringing them in a ‘shopping bag’. That way, your anaesthetist can read the labels of each of the containers. This is particularly important if you are taking unusual supplements or those that contain more than one ingredient.


Ideally, you should stop smoking six months before the operation. If you do quit, you may notice that you have a cough and are bringing up some phlegm. This is usually a sign that your lungs are starting to recover from the effects of the nicotine and the smoke. However, you may not have that much time to quit before the operation, or you may be unable to quit entirely. In either case, decreasing the number of cigarettes and the amount smoked of each cigarette will help. Using nicotine gum or a nicotine patch may make it easier, although neither should be used on the day you have your anaesthetic.

Street drugs

It is vital for your anaesthetist to know what drugs you have used in the past and when. Street or ‘recreational’ drugs, such as heroin, LSD and cocaine, can strongly influence the anaesthetic. Cocaine and ecstasy are two drugs that excite the nervous system. They may excite your heart, producing dangerous swings in blood pressure and heart rate, both during and after the operation. Drugs such as LSD can produce hallucinations, which may cause flashbacks in the postoperative period. As a general rule, it is safer not to use any of these drugs for at least one week before your anaesthetic and operation.


Many people think of the ‘premed’ as being a tablet or injection given to produce a state of calmness. In fact, the term premedication refers to the prescribing of all drugs before anaesthesia and surgery.

These drugs may be prescribed to make you less anxious, to relieve pain, to lessen the possibility of your inhaling stomach acid into your lungs, and to lessen the possibility of your having any postoperative nausea and vomiting. In addition, you may also be given antibiotics to reduce the potential for infection. In the past, many of these drugs were given by injection. However, anaesthetic practice has changed and now almost all of these drugs can be given in tablet or liquid form.


If you are extremely anxious, ask your anaesthetist or your surgeon for something to calm you. In the past, many different drugs were used to help patients feel less anxious before anaesthesia. These drugs included barbiturates and antihistamines. Currently, you might receive one of a class of drugs known as benzodiazepines, such as midazolam, temazepam or diazepam. You may be given a single tablet or a prescription for something to take at home the night before the operation. Or you may be given a tablet, or less often, an injection, once you arrive at the hospital. However, many patients are not admitted to hospital until shortly before the operation. Because of this, you might not receive any form of sedative premed.

You may prefer not to receive any form of sedation, as this will enable you to remain in control for as long as possible before your anaesthetic and operation. Another reason is that studies have shown that patients who do not receive any sedation recover from the effects of the anaesthetic more quickly than those who were sedated beforehand. Older patients tend to remain sleepy for longer and may also have some problems with memory when sedated to reduce preoperative anxiety.


In the past, patients were often given an injection of a painkiller, such as pethidine. This injection was designed to help reduce anxiety and also to supplement the drugs given at the time of the anaesthetic. Some patients, such as those undergoing open-heart surgery, may be given an injection of a sedative and a painkiller. This helps to ensure that they are calm before the operation and that the heart is not stressed. Many anaesthetists no longer give pain-relieving drugs until the patient is actually in the Operating Room, unless the patient is already in pain.

If you are taking painkillers, such as narcotics, it is important to continue taking them so that your pain does not get out of control. But your anaesthetist needs to know about them in order to plan which drugs to give you both during and after the operation. (See also ‘Postoperative pain relief’.)


Another group of drugs that you might be given are those that lessen any chance that you might inhale some of the acid contents of your stomach into your lungs, either during or after anaesthesia. If you are so unfortunate as to suffer this complication, there is an immediate possibility of suffocation by any large pieces of partially digested food that are present in your stomach. There is also a later risk of severe pneumonia from the acid contacting delicate lung tissue. This complication is known as pulmonary aspiration of gastric acid and is potentially lethal.

Three types of drugs can be used to lessen the chances of this occurring in patients who are considered at risk.

  1. A drug that will decreases the production of acid, such as cimetidine or ranitidine, which are know as histamine2 (H-2) receptor-blocking agents.
  2. A drug to help neutralize acid in your stomach, such as the antacid sodium citrate. Taken by mouth, sodium citrate makes your stomach contents less acid (by increasing the pH). Unlike other antacids, sodium citrate is a clear liquid and does not contain any small particles that could damage your lungs if you inhale any stomach contents.
  3. A drug to increase the rate at which your stomach empties into the small intestine, thus decreasing the volume of fluid in your stomach. One drug used for this purpose is metoclopramide.

There are no set rules or strict guidelines for the use of any of these drugs. If you were to undergo a caesarean section, you might be given some sodium citrate. Some anaesthetists use H-2 receptor blockers in patients who have a hiatus hernia or heartburn. If you are extremely obese (fat), then you might be given all three types of drugs. (People who are very fat tend to have large volumes of very acid fluid in the stomach.


Antiemetics are now commonly administered routinely, especially if you have suffered from nausea and vomiting after a previous procedure. There are a variety of antiemetics, which may be given by various routes, however, they are usually administered intravenously after the start of the anaesthetic. Some, like ondansetron, may be taken orally.


In addition, your surgeon may ask that you be given a dose of antibiotics before the procedure, because the prophylactic use of antibiotics has been shown to reduce the possibility of infection. You are most likely to be given ‘prophylactic’ antibiotics if you are to undergo almost any type of major operation, such as a hip replacement, and even some more minor ones, such as a simple hernia repair. Your surgeon may also order antibiotics if you are having a device, such as a pacemaker, implanted. Generally, your anaesthetist is not responsible for ordering antibiotics for this purpose, although he or she might order ‘prophylactic’ antibiotics if you have problems with your heart valves. (Another doctor, such as a heart specialist or surgeon, may also take responsibility for ordering them.)

Sometimes these antibiotics are given in the hour before the operation. In other cases your anaesthetist administers them, usually at the start of the anaesthetic. This ensures that the amount of antibiotic in your blood is as high as possible at the time of the operation.

How does anesthesia work

Depending on the type of pain relief needed, the anesthesiologist (a medical doctor trained in anesthesia and perioperative medicine) delivers anesthetics by injection, inhalation, topical lotion, spray, eye drops, or skin patch. Anesthesiologists are also experts in pain management, they often advise patients and their doctors on how to manage pain.

In preparing for a medical procedure, the anesthesiologist giving anesthesia will choose and determine the doses of one or more drugs to achieve the types and degree of anesthesia characteristics appropriate for the type of procedure and the particular patient. The types of drugs used include general anesthetics, hypnotics, sedatives, neuromuscular-blocking drugs, narcotic, and analgesics.

For many years, doctors called general anesthetics a “modern mystery.” Even though they safely administered anesthetics to millions of Americans, they didn’t know exactly how the drugs produced the different states of general anesthesia. These states include unconsciousness, immobility, analgesia (lack of pain) and amnesia (lack of memory). Understanding anesthetics has been challenging for a number of reasons. Unlike many drugs that act on a limited number of proteins in the body, anesthetics interact with seemingly countless proteins and other molecules. Additionally, some anesthesiologists believe that anesthetics may work through a number of different molecular pathways. This means no single molecular target may be required for an anesthetic to work, or no single molecular target can do the job without the help of others. Most researchers agree that the anesthetic drugs target proteins in the membranes around nerve cells. Because inhaled anesthetics have different effects than intravenous ones, scientists suspect that the two different types of drugs target different sets of proteins.

The anesthesiologist will be there before, during, and after the operation to monitor the anesthetic and ensure you constantly receive the right dose.

The anesthesiologist uses highly advanced electronic devices that constantly display patients’ blood pressure, blood oxygen levels, heart function, and breathing patterns. These devices have dramatically improved the safety of general anesthesia. They also make it possible to operate on many patients who used to be considered too sick to have surgery.

In addition to giving anesthesia medicine to prepare you for the surgery, the anesthesiologist will:

  • monitor your major bodily functions (such as breathing, heart rate and rhythm, body temperature, blood pressure, and blood oxygen levels) during surgery
  • address any problems that might arise during surgery
  • manage any pain you may have after surgery
  • keep you as comfortable as possible before, during, and after surgery.

With general anesthesia, the anesthesiologist uses a combination of various medications to do things like:

  • relieve anxiety
  • keep you asleep
  • minimize pain during surgery and relieve pain afterward (using drugs called analgesics)
  • relax the muscles, which helps to keep you still
  • block out the memory of the surgery.

To better understand how the different types of anesthesia work, it may help to learn a little about the nervous system. If you think of the brain as a central computer that controls all the functions of your body, then the nervous system is like a network that relays messages back and forth from it to different parts of the body. It does this via the spinal cord, which runs from the brain down through the backbone and contains threadlike nerves that branch out to every organ and body part.

Often, anesthesiologists may give a person a sedative to help them feel sleepy or relaxed before a procedure. Then, people who are getting general anesthesia may get medication through a breathing mask first and then be given an IV after they’re asleep. Why? Many people are afraid of needles and may have a hard time staying still and calm, so doctors may need to help them relax first with this medicine.

During your anaesthetic

There are three phases to any anaesthetic.

  • Start or induction phase: In the case of a general anaesthetic the anaesthetist gives you the drugs that make you lose consciousness, or he or she performs the nerve block that makes part of you numb (as in a spinal or an epidural).

In some hospitals, you are taken directly into the Operating Room and then given your anaesthetic. In other hospitals, you are taken into a smaller room adjacent to the Operating Room. This smaller room is known as the Anaesthetic Induction Room, as it is where the anaesthetic is ‘induced’ or started.

In either case, you will have ‘routine monitors’ attached, which are used for virtually every patient. These include an ECG ( electrocardiograph), a pulse oximeter probe, and a blood pressure cuff. In addition, in most cases an intravenous line is started, usually in a vein in the back of one of your hands or in a vein in your forearm.

  • Middle or maintenance phase: The anaesthetist ensures that you remain anaesthetised until the surgical, diagnostic or other treatment procedure is completed.
  • End or emergence phase: The anaesthetist stops giving you the anaesthetic drugs, allows them to wear off, and/or gives you other drugs to reverse their effects, so that you regain consciousness or sensation.

Types of anesthesia

Local anesthesia

An anesthetic drug (which can be given as a shot, spray, or ointment) numbs only a small, specific area of the body (for example, a foot, a single tooth, a hand, a toe or a patch of skin). With local anesthesia, a person is awake and comfortable or sedated, depending on what is needed. Local anesthesia lasts for a short period of time and is often used for minor outpatient procedures (when patients come in for surgery and can go home that same day). For someone having outpatient surgery in a clinic or doctor’s office (such as the dentist or dermatologist), this is probably the type of anesthetic used. The medicine used can numb the area during the procedure and for a short time afterwards to help control post-surgery discomfort.

Local anesthesia are often used in dentistry, for eye surgeries such as cataract removal, and to remove small skin growths including warts and moles.

Regional anesthesia

Regional anesthetics affect larger areas, such as an arm, a leg or everything below the waist. An anesthetic drug is injected near a cluster of nerves, which block transmission of nerve impulses between a targeted part of the body and the central nervous system, causing loss of sensation in the targeted body part – numbing a larger area of the body e.g. epidural anesthesia (such as below the waist, like epidurals given to women in labor) and spinal anesthesia. This type of anesthesia is used for hand and joint surgeries, to ease the pain of childbirth, or during a C-section delivery. A patient under regional or local anesthesia remains conscious, unless general anesthesia or sedation is administered at the same time. Regional anesthesia is generally used to make a person more comfortable during and after the surgical procedure. Regional and general anesthesia are often combined.

Local anaesthetic nerve blocks

The term ‘regional’ refers to the fact that only part of the body is anaesthetised. In some parts of the world, ‘ regional anaesthesia’ may be known as ‘ local anaesthesia’. The term ‘ nerve block’ means that the transmission of impulses in the nerve or nerves from the area of the operation is blocked by the injection of local anaesthetic drugs around the nerve(s). You will feel numb or ‘frozen’ in the area of the block. Local anaesthetics can be administered around the nerves in the spinal cord, either as a spinal or as an epidural anaesthetic. Local anaesthetics can also be injected close to other nerves, such as those in the arms or legs. Because these nerves tend to be in the body’s extremities, these nerve blocks may be called peripheral nerve blocks.

Local anaesthetics may also be used to numb certain internal membranes such as the lining of the mouth or throat, or the urethra for examination of the bladder.

The choice of which particular block to use is based in part on the anaesthetist’s experience and the potential for the block to cause side-effects. The major problems that occur with nerve blocks are related to the needle and to the agent injected. The needle can cause damage to nerves and to other neighbouring structures. For example, a block of the major group of nerves to the arm, when performed at a site just above the collarbone (‘supraclavicular approach to the brachial plexus’) is associated with a 1 or 2 per cent risk of damage to the lung (pneumothorax). This is because of the nerves are close to the outer lining of the lung.

Injection of local anaesthetic agents can cause side-effects because of allergic reactions, or because of misplacement of the needle. Because an artery and vein surround each nerve, it is possible to inject local anaesthetic into either of these blood vessels. This results in a sudden increase in the concentration of local anaesthetic in the bloodstream, which can cause convulsions and cardiac arrest. To reduce the chances of these complications, nerve blocks should be performed in the Operating Room or in a specially equipped room, where monitors and resuscitation equipment are available. This equipment includes oxygen, a means of delivering the oxygen to the lungs, suction apparatus (in case of vomiting), and items for tracheal intubation. It is vital to have properly trained assistance available.

There are different types of local anaesthetics that act for different lengths of time. By choosing various drugs, your anaesthetist can tailor the length of your anaesthetic to match the length of the operation. Sometimes the anaesthetist inserts a fine plastic tube through the nerve block needle. This allows your anaesthetist to give you one or more injections of local anaesthetic, without having to re-insert the needle. This is known as giving a ‘top-up’.

Testing the block

Your anaesthetist then checks to see how well the block has worked, by touching your skin with an ice cube or an alcohol swab. If the block has worked, you cannot feel ‘cold’ when touched. Some anaesthetists use a very fine sterile needle and ask you if the needle feels ‘sharp’ (where the area supplied by the nerve is not blocked) or ‘blunt’ (where the nerve is blocked).

What will you feel ?

The aim of any nerve block is to stop you feeling any pain. However, it is important to remember that you might feel touch, pressure, or vibration, and this is considered normal for certain blocks using certain drugs.

Most anaesthetists like to remind their patients that they may feel ‘something’ but are very unlikely to feel pain. If the block does not work, there are several options:

  • The block can be repeated.
  • If the area of sensation is small, the surgeon might be able to inject a small amount of local anaesthetic into the area where you felt the pain.
  • Your anaesthetist can give you some medication for pain, such as a low concentration of nitrous oxide or a small amount of an injected opiate or narcotic.
  • A general anaesthetic may be given instead.
  • Finally, in some patients, it is better to cancel the procedure and try again another day.

During the Procedure

After determining that your block has worked, your anaesthetist helps the nurse to set up the sterile drapes or sheets that separate you from where the surgeon is working. These drapes also prevent you from seeing what is being done. Your anaesthetist continues to monitor how you feel in general, and your vital signs (blood pressure, heart rate, and oxygen saturation). During the course of the procedure, depending on how you are feeling, your anaesthetist might choose to give you an intravenous injection of a sedative, to relax you. You will feel drowsy and might even drift off into what seems like a light sleep. At the end of the operation you will probably not remember much about the events in the Operating Room. When you are transferred to the recovery room, you feel relaxed, free of pain and quite awake.

Spinal anaesthesia

The most common types of nerve blocks are spinals and epidurals. The spinal cord is surrounded by fluid within a tough fibrous envelope called the ‘dura’. With a spinal, the drug is injected into the fluid. With an epidural, the drug is placed outside the dura, but still within the hollow spinal canal of the backbone.

Spinal anaesthetics are useful for surgical procedures involving the legs and lower abdomen. Typical surgical procedures include caesarean section, vaginal hysterectomy, operations on the prostate, repair of inguinal or groin hernias, repair of a fractured hip, and arthroscopic examination of the knee.

There are a few reasons why you might not be suitable for a spinal anaesthetic. It might be your choice not to have a spinal. The other major reasons have to do with an increased risk of complications from this technique. These include an infection at the site where the needle is inserted, increased pressure around the brain (from a tumour, a build-up of spinal fluid, or the presence of a blood clot) and problems with poor blood clotting. All of these are extremely rare.

If you have a spinal anaesthetic, your anaesthetist first attaches various monitors (ECG, blood pressure cuff, pulse oximeter), and starts an intravenous line. You are then positioned, either lying on one side or sitting up on the edge of the Operating Room table or trolley. If you are lying down, you are asked to curl up into a ball, with your knees drawn up to your chin (or as high as possible). If you are sitting up, you lean over a pillow placed on a small table. In either case, a nurse or the anaesthetist’s assistant helps you to get into position and to remain as still as possible. You have a sheet or blanket to cover your chest and the lower half of your body.

Then your anaesthetist feels the bones of your back to choose the level to insert the spinal needle. The site most often chosen is about 4 – 5 centimetres below your waist and right in the middle (‘midline’). After this, your anaesthetist scrubs up, and puts on sterile gloves and often a sterile gown as well. After washing a small area in the middle of your back, using antiseptic solution (which is usually cold), the anaesthetist covers the surrounding skin with sterile cloths.

The next step is insertion of the needle, during which it is extremely important for you to hold as still as possible. Your anaesthetist first gives you a small injection of some local anaesthetic into the area where the spinal needle will be inserted. This injection might feel like a small bee-sting. Then the specially designed spinal needle is inserted into the epidural space and through the covering over the spinal cord (dura). Sometimes there is a tiny ‘pop’ or ‘click’ when this happens. Once the spinal needle penetrates the dura, it sits in the spinal canal. This is a sack-like structure containing the cerebrospinal fluid, nerve roots, and the spinal cord. Local anaesthetics (and sometimes a painkiller) are injected into the spinal fluid through the needle, which is then removed.

After the needle is removed, it is safe for you to move a little bit. If you are sitting up, your anaesthetist has you lie down after about 30 seconds. If you were lying down, you continue to lie in that position, although you could straighten your legs and your neck. The local anaesthetic solution disperses in the spinal fluid and blocks the nerves. Over the next few minutes you develop profound numbness and weakness in the lower half of your body (or one side more than the other if the spinal was inserted when you were lying on one side).

The major immediate complications of spinal anaesthetics include nerve damage from the needle, a decrease in blood pressure and heart rate, and failure of the injection to produce an adequate level of anaesthesia. The chance of the block not working is about one per cent or less, depending on how frequently your anaesthetist performs spinal blocks.

The long-term complications of spinal anaesthesia include a 1 per cent chance of severe headache afterwards. Termed a post-dural puncture headache, this type of headache is unusual in that it comes on when a patient sits or stands up and is completely resolved by lying down. (The medical term for this phenomenon is ‘posturally dependent headache’.) Specific treatment may be needed for the headache.

One extremely rare complication of spinal anaesthesia includes compression of the spinal cord from a blood clot or abscess in the spinal canal. Another rare complication is ongoing nerve damage from chemical effects of the anaesthetic or other agents on the nerve roots.

A slightly more common complaint is irritation of a nerve root (radicular irritation syndrome). With this problem, patients report burning pain in the legs. The pain comes on a few days after having a spinal with certain local anaesthetic drugs. Fortunately, the pain goes away without any treatment.

Epidural anaesthesia

Like spinal anaesthesia, epidural anaesthesia can be used for operations on the legs and the lower part of the abdomen. Epidurals can also be inserted to help with pain management, either after an operation or during labor.

The spinal cord is surrounded by fluid within a tough fibrous envelope called the ‘dura’. With a spinal, the drug is injected into the fluid. With an epidural, the drug is placed outside the dura, but still within the hollow spinal canal of the backbone. The technique of insertion of the epidural needle is similar to that used for spinal anaesthesia. However, the needle is stopped in the epidural space and there is no attempt to penetrate the dura. Usually, epidural anaesthesia is performed using a larger needle through which a fine plastic tube (catheter) can be threaded into the epidural space. This tube is similar to fine cooked spaghetti and it is not always possible to determine where the tip of the catheter ends up. Occasionally a patient complains of a brief, shock-like sensation as the catheter is being threaded through the needle and into the back. Most anaesthetists warn their patients that this might happen and remind them not to move until the needle is withdrawn. Once the catheter is well situated, the needle is removed. The catheter is then taped up the back and secured to the hospital gown. A filter is attached to the catheter – in case the fluid to be injected contains tiny particles of glass from the drug ampoules, and to keep bacteria out.

Epidurals are often inserted to relieve the pain of labor and childbirth, as well as postoperative pain. In such cases, epidural analgesia is provided instead of epidural anaesthesia. The only difference between anaesthesia and analgesia is that analgesia uses weaker concentrations of local anaesthetic. An opiate or narcotic may also be injected into the epidural to increase pain relief. Epidurals differ from spinals in that a much larger dose of local anaesthetic is required for an epidural anaesthetic as compared to a spinal anaesthetic.

Epidurals can be inserted into the upper part of the back (the thoracic spine), and are then known as thoracic epidurals. These are particularly useful for the relief of postoperative pain after operations on the chest (thoracic surgery). In addition, the anaesthetist may use the pain relief from the epidural to reduce the amount of general anaesthetic needed during the operation.

The immediate risks from epidural anaesthesia include a decrease in blood pressure, and seizures from the accidental intravenous injection of local anaesthetic agents. In addition, effects similar to spinal anaesthesia can be seen, but because of the larger dose of local anaesthetic used with epidurals, the patient may be anaesthetised from the neck down.

The long-term complications of epidural anaesthesia include a less than 1 per cent chance the block failing to work, and a similar chance of having a post-dural puncture headache. Also possible is damage to a nerve root from the epidural needle or catheter. In extremely rare cases, an epidural blood clot ( haematoma) or abscess may occur, resulting in weakness of the legs and in loss of bowel and bladder control.

Other nerve blocks

Other parts or regions of the body can also be anaesthetised (‘frozen’) – for example, for operations on an eye, arm, or foot. Many different techniques have been described for such operations.

Operations on the eye can be performed under retrobulbar or peribulbar block. These blocks involve injecting local anaesthetic around the eyeball, so that the eye is pain-free and unable to move. This kind of block is used for many operations on the eye, including cataract extraction with lens insertion and repair of defects on the retina (back of the eye). Some cataract operations can also be performed under local anaesthesia, after local anaesthetic drops have been applied to the surface of the eye.

For surgery on the arm it is possible to provide satisfactory anaesthesia by blocking the major group of nerves (brachial nerve plexus) that supplies the shoulder and arm. A block may be performed at one of a number of different sites, including:

  • in the neck (interscalene)
  • above the collar bone (supraclavicular)
  • below the collar bone (infraclavicular)
  • and in the armpit (axillary).

For surgery on the leg it is possible to provide satisfactory anaesthesia by blocking the major group of nerves (sciatic nerve or femoral nerve) that supplies the hip, leg and foot. A block may be performed at one of a number of sites, including:

  • in the groin (inguinal)
  • under the buttocks
  • at the back of the knee (popliteal fossa)
  • and at the ankle.

The intravenous technique, or Bier’s block, can be used for operations on the arm, such as reduction of simple fractures of the wrist, and less commonly for procedures on the leg. With this technique, a special tourniquet with two cuffs is wrapped around the arm or leg to be anaesthetised. An intravenous cannula is inserted into a vein in the hand or foot, but no intravenous line is attached. The anaesthetist then lifts up the arm or leg and wraps a tight rubber bandage around it, to drain the blood. The tourniquet cuff closer to the head is then inflated and the rubber bandage is removed. The arm or leg is lowered and local anaesthetic is injected through the intravenous cannula. After at least five minutes, the lower tourniquet cuff is inflated. Once this has been secured, the upper cuff is released. This sequence ensures that the patient does not feel any pain from the tourniquet, which must remain inflated for at least 45 minutes. If the tourniquet is released prematurely, there would be an increased chance that the local anaesthetic will rush through the patient’s blood vessels to the heart and brain. The effect on the heart would be to decrease the heart rate and blood pressure. The effect on the brain might be to cause seizures or loss of consciousness.

General anesthesia

General anesthesia suppresses central nervous system activity and results in unconsciousness, complete muscle paralysis and total lack of sensation 2). The goal is to make and keep a person completely unconscious (or “asleep”) during the operation, with no awareness or memory of the surgery. General anesthesia can be given through an IV (which requires sticking a needle into a vein, usually in the arm) or by inhaling gases or vapors by breathing into a mask or tube. General anesthesia delivered intravenously will act quickly and disappear rapidly from the body. This allows patients to go home sooner after surgery. Inhaled anesthetics may take longer to wear off.

Surgeons use general anesthesia when they operate on internal organs and for other invasive or time-consuming procedures such as back surgery. Without general anesthesia, many major, life-saving procedures would not be possible, including open-heart surgery, brain surgery and organ transplants.

General anesthetics typically are very safe. But they can pose risks for some patients, such as the elderly or people with chronic illnesses such as diabetes. Also, side effects may linger for several days in some patients, especially the elderly and children.

General anesthesia side effects

General anesthesia is overall very safe; most people, even those with significant health conditions, are able to undergo general anesthesia itself without serious problems.

General anesthetics side effects—such as dangerously low blood pressure—are much less common than they once were. Still, as with any medical procedure, some risks exist. To minimize these risks, specialized doctors called anesthesiologists carefully monitor unconscious patients and can adjust the amount of anesthetic the patients receive.

In fact, your risk of complications is more closely related to the type of procedure you’re undergoing and your general physical health, rather than to the type of anesthesia.

Older adults, or those with serious medical problems, particularly those undergoing more extensive procedures, may be at increased risk of postoperative confusion, pneumonia, or even stroke and heart attack.

Specific conditions that can increase your risk of complications during surgery include:

  • Smoking
  • Seizures
  • Obstructive sleep apnea
  • Obesity
  • High blood pressure
  • Diabetes
  • Other medical conditions involving your heart, lungs or kidneys
  • Medications, such as aspirin, that can increase bleeding
  • History of heavy alcohol use
  • Drug allergies
  • History of adverse reactions to anesthesia

These risks are generally related to the surgery itself, not the anesthesia.

What is Anesthesia awareness ?

Estimates vary, but about 1 or 2 people in every 10,000 may be partially awake during general anesthesia and experience what is called unintended intraoperative awareness. It is even rarer to experience pain, but this can occur as well.

Because of the muscle relaxants given before surgery, people are unable to move or speak to let doctors know that they are awake or experiencing pain. For some patients, this may cause long-term psychological problems, similar to post-traumatic stress disorder.

This phenomenon is so rare that it’s difficult to make clear connections. Some factors that may be involved include:

  • Emergency surgery
  • Cesarean delivery
  • Depression
  • Use of certain medications
  • Heart or lung problems
  • Daily alcohol use
  • Lower anesthesia doses than are necessary used during procedure
  • Errors by the anesthesiologist, such as not monitoring the patient or not measuring the amount of anesthesia in the patient’s system throughout the procedure.

How you prepare for a general anesthesia

General anesthesia relaxes the muscles in your digestive tract and airway that keep food and acid from passing from your stomach into your lungs. Always follow your doctor’s instructions about avoiding food and drink before surgery.

Fasting is usually necessary starting about six hours before your surgery. You may be able to drink clear fluids until a few hours prior.

Your doctor may tell you to take some of your regular medications with a small sip of water during your fasting time. Discuss your medications with your doctor.

You may need to avoid some medications, such as aspirin and some other over-the-counter blood thinners, for at least a week before your procedure. These medications may cause complications during surgery.

Some vitamins and herbal remedies, such as ginseng, garlic, Ginkgo biloba, St. John’s wort, kava and others, may cause complications during surgery. Discuss the types of dietary supplements you take with your doctor before your surgery.

If you have diabetes, talk with your doctor about any changes to your medications during the fasting period. Usually you won’t take oral diabetes medication the morning of your surgery. If you take insulin, your doctor may recommend a reduced dose.

If you have sleep apnea, discuss your condition with your doctor. The anesthesiologist or anesthetist will need to carefully monitor your breathing during and after your surgery.

What you can expect from a general anesthesia

Before the procedure

Before you undergo general anesthesia, your anesthesiologist will talk with you and may ask questions about:

  • Your health history
  • Your prescription medications, over-the-counter medications and herbal supplements
  • Allergies
  • Your past experiences with anesthesia

This will help your anesthesiologist choose the medications that will be the safest for you.

During the procedure

Your anesthesiologist usually delivers the anesthesia medications through an intravenous line in your arm. Sometimes you may be given a gas that you breathe from a mask. Children may prefer to go to sleep with a mask.

Once you’re asleep, the anesthesiologist may insert a tube into your mouth and down your windpipe. The tube ensures that you get enough oxygen and protects your lungs from blood or other fluids, such as stomach fluids. You’ll be given muscle relaxants before doctors insert the tube to relax the muscles in your windpipe.

Your doctor may use other options, such as a laryngeal airway mask, to help manage your breathing during surgery.

Someone from the anesthesia care team monitors you continuously while you sleep. He or she will adjust your medications, breathing, temperature, fluids and blood pressure as needed. Any issues that occur during the surgery are corrected with additional medications, fluids and, sometimes, blood transfusions.

Blood transfusions may sometimes be necessary, such as during complex surgeries. The anesthesia care team monitors your condition and delivers blood transfusions when needed. Blood transfusions may involve risks. These risks are greater in people who are older, have low red blood cell volume or are undergoing complex heart surgeries.

After the procedure

When the surgery is complete, the anesthesia medications are stopped, and you slowly wake either in the operating room or the recovery room. You’ll probably feel groggy and a little confused when you first wake. You may experience common side effects such as:

  • Nausea
  • Vomiting
  • Dry mouth
  • Sore throat
  • Shivering
  • Sleepiness
  • Mild hoarseness

You may also experience other side effects after you awaken from anesthesia, such as pain. Side effects depend on your individual condition and the type of surgery. Your doctor may give you medications after your procedure to reduce pain and nausea.

What Type of Anesthesia Will You Get ?

The type and amount of anesthesia given to you will be specifically tailored to your needs and will depend on various factors, including:

  • the type of surgery
  • the location of the surgery
  • how long the surgery may take
  • your current and previous medical condition
  • allergies you may have
  • previous reactions to anesthesia (in you or family members)
  • medications you are taking
  • your age, height, and weight

The anesthesiologist can discuss the options available, and he or she will make the decision based on your individual needs and best interests.

Before Surgery

Although you may be able to talk to the anesthesiologist a day or two prior to the operation, you might not meet until that day. Either way, the anesthesiologist will go over your medical history and information thoroughly, so that he or she can make the right choice regarding anesthetic medications tailored to your individual needs.

To ensure your safety during the surgery, you’ll need to answer all of the anesthesiologist’s questions as honestly and thoroughly as possible. Things that may seem harmless could interact with or affect the anesthesia and how you react to it.

The anesthesiologist might order additional tests (such as X-rays or blood or laboratory tests) to help figure out the best possible personalized anesthetic plan for you.

In addition to doing a physical examination of your airways, heart, and lungs, the anesthesiologist will also want to get your medical history, which will include asking about:

  • your current and past health
  • your family’s health
  • any medications, supplements, or herbal remedies you are taking (consider bringing a list of exactly what you take, detailing how much and how often)
  • any previous reactions you or any blood relative has had to anesthesia
  • any allergies (especially to foods, medications, or latex) you may have
  • whether you smoke, drink alcohol, or take recreational drugs.

Eating and Drinking Before Anesthesia

The anesthesiologist, surgeon, or someone on the nursing staff will give you instructions about not eating or drinking before surgery. It’s important to make sure you don’t eat anything prior to surgery (usually nothing after midnight the day before the operation). You’ll get specific instructions based on your age, medical condition, and the time of day of the procedure.

Why is fasting important ?

If you vomit when you are awake, or even when you are asleep at night (and not anaesthetised), your reflexes prevent any of that vomit being aspirated (or inhaled) into your lungs. You cough and splutter to clear the area around the back of your throat and larynx. Then you can breathe again.

When anaesthetised (or very drunk, or affected by an overdose of sedatives or certain street drugs), you may be able to vomit but some of your protective reflexes do not work. There is therefore a possibility that fluid from the stomach will regurgitate – that is, run up your oesophagus and into the back of your throat. Should this happen when your level of consciousness is decreased, then you cannot protect yourself by swallowing and coughing. The fluid may then pass into your windpipe or trachea and down into your lungs. This is known as aspiration. Should you inhale some stomach contents, then there is the risk of suffocation, particularly if undigested food is present. The acid in your lungs may also cause severe wheezing and a lack of oxygen. Later, pneumonia may develop. This pneumonia is a particularly severe form because of the effect of the acid on the delicate tissue of the lungs.

How long do patients go without food or drink ?

Until about ten years ago, it was common for patients scheduled for elective surgery to fast from midnight on the night before surgery. If the operation was scheduled in the afternoon, patients had to fast for periods of up to 16 – 18 hours. In the late 1980s, a number of scientific studies were carried out that questioned the validity of this fasting policy. In some countries, professional organisations have changed their recommendations to allow shorter hours of fasting. For example, the Canadian Anaesthetists’ Society produced a revision to the Guidelines to the Practice of Anaesthesia in 1996. These new guidelines stated that fasting policies should take into account the age of the patient, as well as any medical problems that the patient might have. The guidelines also recommended that a patient should not eat any solid foods on the day of surgery, but could drink clear fluids up to three hours before the operation. Despite increasing amounts of scientific evidence about the safety of following guidelines such as these, standard textbooks of anaesthesia still recommend that patients be ‘ NPO ’ (‘Nil per os’ or ‘nothing by mouth’) for six to eight hours before anaesthesia and surgery. It is likely that such statements will change in the future, although anaesthetists still recommend in general that patients do not eat any solid food after midnight before the scheduled operation.

Emergency surgery

If you have been in an accident, are in pain, or have been given an injection of a painkiller, the speed at which food leaves your stomach and passes downwards is slowed. This results in you having what anaesthetists term a ‘ full stomach’, which increases the possibility of stomach contents being regurgitated back up the throat. Theoretically, your operation could be delayed until your stomach had emptied, although this is not always appropriate. There are ways of minimising the possibility of regurgitation of gastric contents. Some patients may need to have a nasogastric inserted through the nose, down the oesophagus, and into the stomach. The fluid in the stomach can then be suctioned out through the tube, although removing solids is still a problem. This technique is important in patients who have an obstruction of the bowel. Unfortunately, suctioning cannot ensure that the stomach is empty, but only one that is ‘less full’. Drugs that are currently used to lessen the risk of regurgitation include those to neutralize stomach acid, those to decrease acid production, and those to increase the downward emptying of the stomach.

If you are sick

In general, you should be as well as possible before undergoing any anaesthetic or surgery. Sometimes, of course, surgery is necessary and there may even be some degree of urgency to have the operation. Your surgeon, perhaps together with your anaesthetist, can weigh up your need for the operation and how urgent it is against any illness or condition you have. If you are scheduled for elective surgery, it is usual to delay the operation if you become unwell. In most cases, an optimal time will be suggested.

The final decision as to whether or not to delay your operation rests with your anaesthetist and your surgeon. It is best to contact them if you become unwell in the days leading up to your appointment. You may also wish to contact your family doctor for advice and possible treatment.

If you have a cold or the flu, it is likely that your anaesthetic and operation will be postponed. If you have a sore throat with no other symptoms, then your anaesthetist may consider that you can proceed, although your throat may be very sore afterwards. If the sore throat is an early sign of the development of a cold or the flu (and it isn’t always), then the resulting illness may be hastened and you may feel extremely unwell after the operation. Again, the decision to proceed rests with your anaesthetist and your surgeon, although if you decide not to proceed your wishes will be respected.

There is an increased probability of respiratory complications when anaesthesia is administered to a patient with an established cold or influenza. Your anaesthetist, however, is aware of the potential for complications and of the means of managing them safely. Diarrhoea is not a contraindication to anaesthesia or surgery unless it is part of a more generalised illness. One of the benefits of the developments in anaesthetic drugs and techniques is that anaesthesia is now relatively safe, even in patients who are severely ill.

In the Operating Room

If general anesthesia is used, the anesthesiologist will start transitioning you from the normal awake state to the sleepy state of anesthesia. This is called induction, which is usually done by either injecting medicine through an IV or by inhaling gases through a mask.

If, like lots of people, you’re afraid of needles, the good news is that you may not have to get one while awake. Anesthesiologists often will begin the induction process by using a breathing mask to help you relax. The mask delivers medication to make you sleepy before and during the surgery. That way, you won’t be awake when the IV is inserted for general anesthesia or when a shot is given to numb a certain part or area of the body for local or regional anesthesia.

When using general anesthesia, the anesthesiologist will monitor your vital signs, continue to deliver anesthesia, and keep you as comfortable as possible throughout the operation.

To help you breathe and/or to help deliver general anesthesia during the operation, the anesthesiologist might use an endotracheal tube (a plastic tube that’s placed into the windpipe through the mouth or nose) or laryngeal mask airway (or LMA — a mask with a tube that fits into the back of the mouth).

After Surgery

Once the operation or procedure is over, you’ll be taken to the recovery room or PACU (post-anesthesia care unit). In the PACU, nurses and the anesthesiologist will monitor your condition very closely to make sure you are making a smooth and comfortable transition from an anesthetized state to an awakened state.

If you had general anesthesia or were sedated, don’t expect to be fully awake right away — it may take a while and you may doze off for a bit. It usually takes about 45 minutes to an hour to recover completely from general anesthesia. In some cases, this period may be a bit longer depending on medications given during or after surgery.

Although every person has a different experience, you may feel groggy, confused, chilly, nauseated, scared, alarmed, or even sad as you wake up. Depending on the procedure or surgery, you may also have some pain and discomfort afterward, which the anesthesiologist can relieve with medications. When you have recovered from the anesthesia, you’ll be evaluated to make sure you’re ready to leave the recovery room.

In many outpatient procedures, people are allowed to come home soon after the surgery is done. Before you leave the hospital, you’ll receive instructions for further recuperation at home and for a follow-up visit with the surgeon. Talk to the surgeon and/or the anesthesiologist about what to expect after the surgery and how you can stay as comfortable as possible.

Anesthesia is very safe. In today’s hospitals and surgery centers, highly trained professionals use a wide variety of modern medications and extremely capable monitoring technology to ensure that people are stable and as comfortable as possible before, during, and after their procedure.

Anesthesia drugs

Infiltrative anesthetics (for Local and Regional Anesthesia, sometimes in General Anesthesia for pain relief post op)

Infiltrative anesthesia is often administered in the office setting for local anesthesia.

There are two classes of infiltrative anesthetics, amides and esters, which create a reversible blockade of sodium channels within the nerve fibers 3). When choosing an anesthetic agent, it is important to consider the type of procedure, the length of time required for anesthesia, and the pharmacodynamics of each medication. Table 1 is an overview of commonly used infiltrative anesthetic agents 4). True allergies to local anesthetics are rare, especially with amide preparations 5). However, evidence suggests there is cross reactivity between agents within the same class 6). In patients with a possible allergy, skin testing should be considered when immunoglobulin E–mediated reactions cannot be ruled out using the history 7).

Anesthetic Agents

Lidocaine (Xylocaine), an amide, is the most commonly used infiltrative anesthetic and is available in several concentrations 8). For most procedures, a 0.5% or 1% solution is appropriate. Higher concentrations of lidocaine do not improve onset or duration of action and may increase the risk of toxicity 9). Adding epinephrine (concentration of 1:100,000 or 1:200,000) prolongs the duration of anesthesia, increases the maximum dose, and may aid hemostasis 10). Contrary to longstanding belief, the use of lidocaine with epinephrine on the nose, ears, digits, and penis appears to be safe 11), 12). However, many physicians still choose to avoid epinephrine use in these areas. Epinephrine should not be used in patients with peripheral artery disease.

Bupivacaine (Marcaine) is a widely used amide. It has a prolonged duration of action, but this also increases the risk of toxicity (4:1 risk of toxicity compared with lidocaine) and can cause a dose-dependent widening of the QRS interval, leading to ventricular fibrillation 13). Bupivacaine is contraindicated in pregnant women because of the increased bio-availability from decreased venous return 14).

Procaine (Novocain) and tetracaine (Pontocaine) are most often used for dental, topical, spinal, and epidural anesthesia.

Table 1. Commonly Used Infiltrative Anesthetic Agents

AgentConcentrationOnset*Duration*Maximum dose
mg per kgmL


Lidocaine (Xylocaine)

0.5%, 1%, or 2%†

Rapid: < 2 minutes

30 to 60 minutes

4 (up to 300 mg per dose)

0.5%: 60 1%: 30 2%: 15

Lidocaine with epinephrine‡

1% or 2%

Rapid: < 2 minutes§

1 to 4 hours

7 (up to 500 mg per dose)

1%: 50 2%: 25

Bupivacaine (Marcaine)

0.25% or 0.5%

Slow: 5 minutes

2 to 4 hours

2 (up to 175 mg per dose)

0.25%: 70 0.5%: 35


Procaine (Novocain)

1% or 2%

Moderate: 2 to 5 minutes

15 to 60 minutes

7 (up to 600 mg per dose)

1%: 60 2%: 30

Tetracaine (Pontocaine)


Slow: 5 to 10 minutes

2 to 3 hours

1.4 (up to 120 mg per dose)


*—Similar for all concentrations of each agent.

†—Higher concentrations provide no additional anesthetic effects.

‡—Epinephrine concentration may be 1:100,000 or 1:200,000.

§—May take up to 5 minutes for epinephrine to be effective.

[Source 15)]

General anesthetic

A general anesthetic (or anaesthetic) is a drug that can bring about a reversible loss of consciousness. Anesthesiologist (or anaesthetist) administers these drugs to induce or maintain general anesthesia to facilitate surgery. Some of these drugs are also used in lower dosages for pain management. The biological mechanisms of the action of general anesthetics are not well understood.

Mode of administration. Drugs given to induce general anesthesia can be either as gases or vapors (inhalational anesthetics) or as injections (intravenous anesthetics or even intramuscular). It is possible to deliver anesthesia solely by inhalation or injection, but most commonly the two forms are combined, with an injection given to induce anesthesia and a gas used to maintain it.

Inhalation general anesthetic

Inhalational anaesthetic substances are either volatile liquids or gases, and are usually delivered using an anesthesia machine. An anesthesia machine allows composing a mixture of oxygen, anesthetics and ambient air, delivering it to the patient and monitoring patient and machine parameters. Liquid anesthetics are vaporized in the machine. All of these agents share the property of being quite hydrophobic (i.e., as liquids, they are not freely miscible—or mixable—in water, and as gases they dissolve in oils better than in water).

Many compounds have been used for inhalation anaesthesia, but only a few are still in widespread use.

  • Desflurane, isoflurane and sevoflurane are the most widely used volatile anaesthetics today.

They are often combined with nitrous oxide. Older, less popular, volatile anaesthetics, include halothane, enflurane, and methoxyflurane. Researchers are also actively exploring the use of xenon as an anaesthetic.

Injection general anesthetic

Injectable general anesthetics are used for the induction and maintenance of a state of unconsciousness. Anaesthetists prefer to use intravenous injections, as they are faster, generally less painful and more reliable than intramuscular or subcutaneous injections.

Among the most widely used drugs are:

  • Propofol
  • Etomidate
  • Barbiturates such as methohexital and thiopentone/thiopental
  • Benzodiazepines such as midazolam
  • Ketamine is used in the UK as “field anaesthesia”, for instance at a road traffic incidents or similar situations where an operation must be conducted at the scene or when there is not enough time to move to an operating room, while preferring other anaesthetics where conditions allow their use. It is more frequently used in the operative setting in the US.

Benzodiazepines are sedatives and are used in combinations with other general anesthetics.

Anaesthetic equipment

Some of the drugs given by the anaesthetist are injected, but others are inhaled. To deliver these inhaled drugs, as well as oxygen, your anaesthetist uses an anaesthetic machine.

The anaesthetic machine is not a machine that makes anaesthetics, but a complex collection of equipment. It has three major components: a gas mixing and delivery system; an anaesthetic breathing system ( circuit) and a ventilator; and an array of monitors. Some recently developed machines have highly complex integrated electronic systems and are usually called anaesthesia workstations.

The gas mixing and delivery system

The anaesthetic machine is connected to a supply of purified gases. These gases usually include oxygen and nitrous oxide, and many machines also have a supply of compressed air. All the gases are mixed in a special device, which ensures accurate concentrations and limits the minimum amount of oxygen which can be used. To this gas mixture, the anaesthetist can add one of a range of additional, more powerful anaesthetic agents, known as inhalational agents. These come as a liquid and are placed in a device called a vaporiser, which converts them into a gas and adds them in carefully controlled concentrations to the gas mixture.

The anaesthetic breathing system (circuit) and ventilator

The anaesthetist determines the flow rate of the final mixture of gases supplied to the breathing system. This is a series of hoses about three centimetres in diameter, which connects to either the mask or the endotracheal tube, but also to a ventilator. The breathing circuit is often attached to a container of ‘soda lime’ granules: these absorb carbon dioxide that the patient exhales with each breath.

The ventilator is an automatic breathing device, which takes over the rhythmic inflating and deflating of the patient’s lungs in a programmed manner. The anaesthetist sets the gas flow, the oxygen concentration, the anaesthetic agent concentration, the amount of gas in each breath, and the number of breaths per minute.

The monitors

Some people think that anaesthetists do not do anything during an operation, once the anaesthetic has started. In fact, anaesthetists are very busy, watching and evaluating their patients, the progress of the operation, the surgeon, and all the other members of the Operating Room team. By watching and evaluating – or processing all this information – your anaesthetist is able, if necessary, to make moment-by-moment adjustments to the drugs and fluids that you need during your anaesthetic and operation. Your anaesthetist is also able to consider the plan for the next phases of your care, such as in the recovery room.

Some of the information that your anaesthetist evaluates comes from special monitors. Two kinds of monitors are used to make continuous checks. One kind tells your anaesthetist all about you, including include your heart rate, blood pressure, and temperature. The other kind shows how the anaesthetic machine is functioning.

Measurements of how your body is reacting to the anaesthetic and operation or examination include:

  • Your heart rate (pulse) and rhythm: by feeling the pulse in your wrist or your neck, by using a stethoscope to listen to your heart, and by means of the electrocardiograph (ECG or EKG). The same monitor can also be used to detect if your heart is suffering any strain.
  • Your (arterial) blood pressure: by attaching a traditional inflatable cuff or sometimes by inserting a small tube or cannula (or catheter) directly into an artery.
  • The amount of oxygen in a small or peripheral artery: by attaching a device like a clothes-peg, known as a pulse oximeter to one of your fingers or toes or ear lobes, or to the tip of your nose. The result is known as your arterial oxygen saturation.
  • The amount of carbon dioxide (CO2) you breathe out: by using a carbon dioxide detector. The result is known as your end-tidal (end of each breath) carbon dioxide concentration. This measurement helps your anaesthetist to check on the function of your lungs and on your metabolism. This monitor is also used to ensure that the breathing tube is correctly placed in your windpipe or trachea and that the breathing circuit has not become disconnected.
  • How well you are breathing (or being breathed for): by using a stethoscope, so that your anaesthetist can ensure that your breathing tube is not inserted too deeply and that you do not have any areas of blockage in your lungs. Other methods to measure the adequacy of your breathing include the use of a special meter to assess the size or volume of each breath you take or are given, and a gauge to measure the pressure in your lungs between breaths and the pressure that is required to inflate your lungs with each breath.
  • Your nerve and muscle function: by using a peripheral nerve stimulator to check how the muscle relaxants are affecting your muscle activity and power.
  • Your temperature: by using a thermometer, to ensure that you don’t get too hot or too cold, since you lose some of your ability to control your temperature while anaesthetised.
  • How much urine you are producing: by inserting a catheter into your bladder during some operations and examinations. This allows your bladder to drain freely and also gives your anaesthetist an idea of how well your kidneys are functioning.
  • The pressures in your large veins and your heart: by inserting a special cannula into a large vein in either your neck or arm and passing the cannula through into the large blood vessel (superior vena cava) that leads to the heart. Sometimes the cannula is actually threaded through the chambers of the heart and into your pulmonary artery (which carries blood to the lungs.) As well as pressures, the cannula can determine how much blood your heart is pumping with each beat.
  • The depth of your anaesthetic, and whether or not you are unconscious (if you are having a general anaesthetic): by using a monitor that looks at small electrical impulses or ‘brain waves’ generated by the brain. (This is similar to an ECG of the brain.)This last monitor is not available in many centres. Currently most anaesthetists do not have access to a monitor that indicates if you are adequately anaesthetised or aware of your surroundings. This kind of monitor is still under development. But current anaesthetic practice is different from that of say, ten years ago, in that your anaesthetist can now measure with an anaesthetic agent monitor exactly how much anaesthetic agent you are receiving. This measurement tells your anaesthetist that you are receiving enough anaesthetic gas to ensure that you are unconscious.Your anaesthetist also constantly observes a number of measurements from the anaesthetic machine. These include:
    • the pressure of oxygen and nitrous oxide in the pipelines or tanks on the back of the machine from which these gases are delivered
    • the amount of oxygen flowing to you from the machine
    • the number of times each minute that the breathing machine (or ventilator) delivers a breath to you
    • the amount or concentration of anaesthetic agents in the gas you breathe in and out
    • that you are still connected to the breathing circuit, and that this circuit has not become disconnected.

This last observation is vital, because you may have been given drugs which stop you from breathing. If so, then you must remain connected to the breathing circuit to make sure that you continue to receive oxygen. If your breathing circuit becomes disconnected, you could suffer brain damage or death if the disconnection is not detected in time.

Specialty societies and regulatory bodies in anaesthesia have published guidelines describing the equipment and monitors necessary to provide anaesthetic care.

Examples are:

One function of these guidelines is to provide details of the absolute minimum type and number of monitors that should be present, functioning, and used before an anaesthetic is given. This is similar to the ‘Minimum Equipment List’ required in aviation before a pilot can take off.

By now you should also have an idea of the amount and complexity of information that your anaesthetist must constantly observe and monitor. Currently there is no ‘black box’ like the one used in aviation that can integrate all the measurements and provide a ‘flight profile’ for your anaesthetic and operation. Some new anaesthetic machines do incorporate automated record-keeping systems, which help to document and integrate some of this information. Automated systems offer advantages in that a record can be kept during emergencies when the anaesthetist may be very busy (as described later).

Another similarity with aeroplanes is that the anaesthetic machine also has self-checking and monitoring capabilities, so that problems can be easily identified. There is also always a back-up system, so that if the system fails, or there is a power blackout, the anaesthetist can safely carry the patient through such a crisis. In many ways the anaesthetist is indeed like a pilot, flying the plane, watching the instruments, and looking out the window (at the surgeon), always ready to take control if a problem occurs. This concept is also emphasised in the equipment guidelines mentioned above. In addition to listing pieces of equipment, these documents also recommend that the most important monitor of the anaesthetised patient is the continuous presence of an anaesthetist.

Anesthesia Recovery

After your operation or procedure, you are taken to one of several places. Most commonly, this is the recovery room (RR) where there are a number of other patients (depending on the size of the facility) also recovering from their anaesthetics. Other names for this area include the Post-Anaesthetic Recovery Room (PARR) or the Post-Anaesthesia Care Unit (PACU).

If you have undergone a very minor procedure, usually not involving an operation, and in a small surgical clinic or X-ray facility, you may be taken to a recovery ‘bay’ or place for a single patient. Your care should be the same as you would receive in a Recovery Room.

If you have only a local anaesthetic or monitored anaesthesia care, you might be discharged directly to the day care ward – for example, after cataract surgery under nerve block. Either your surgeon (in the case of local anaesthesia) or your anaesthetist makes this decision, on the basis of your being stable after the procedure and well recovered from any drugs which you have received.

If you were very ill before surgery, or you had major or complicated surgery (for example, open heart surgery), or complications arose during the course of anaesthesia or surgery, then you might be transferred to an intensive care unit (sometimes known as Intensive Therapy Unit) or high dependency unit. (These units are often referred to by their initials: ICU, ITU or HDU.) They offer a more highly specialised level of nursing and medical care.

When you are transferred to the Recovery Room, your anaesthetist provides the Recovery Room nurse with a brief report. This will include a description of:

  • your preoperative condition, including any medical illnesses and medications
  • the surgical procedure
  • the course of the anaesthetic, including any problems with your airway, any need for airway control in the Recovery Room, and the adequacy of recovery of muscle strength
  • intravenous cannulae
  • intraoperative fluid balance ( how much intravenous fluid you were given and how much fluid you lost, including blood loss)
  • any other important information.

While this description is being given, the nurse usually places an oxygen mask over your face to give you extra oxygen, and attaches a blood pressure cuff and a pulse oximeter. You may or may not be conscious at this stage. If you are not, then you will probably be positioned on your side, which may become a little uncomfortable as you awaken. This position, known as the ‘coma position’, is commonly used in any situation where a person’s ability to protect his or her airway may be weakened. In this position, the tongue falls forward, rather than backwards where it may obstruct breathing. In addition, if the person were to regurgitate or vomit, the vomitus would drain away from the mouth and not be sucked into the lungs.

You may still have a plastic airway or breathing tube in place. Exactly when this tube is removed depends in part on your condition and why the tube was inserted, and also on how conscious you are. Your anaesthetist might choose to remove the tube while you are still in the Operating Room. If you are still deeply unconscious when you arrive in the Recovery Room, your anaesthetist might leave the tube in until you ‘lighten’ or regain consciousness. (The process of removing the tube is known as extubation.) To many people, the thought of having a breathing tube in place while awake sounds unpleasant. However, what anaesthetists consider to be ‘awake’ in the Recovery Room is not quite the same as being fully conscious. In fact, being able to open the eyes and mouth and to take a breath on command are signs that you are probably awake enough to have the tube removed. Most patients do not remember any of this.

Once your anaesthetist is confident that your vital signs are stable and that your safety is assured, the process of ‘transfer of care to the Recovery Room nursing staff’ occurs. This means that the nurses are now responsible for your care and your anaesthetist may leave you to return to the Operating Room to start the anaesthetic for the next patient on the surgical list.

Who will look after you ?

The Recovery Room provides specialised nursing staff that has specific training in the management of common problems of partially anaesthetised patients. Following general anaesthesia, patients in the Recovery Room may develop difficulty breathing. For example, after tonsillectomy, there is always the risk of swelling and bleeding from where the tonsils were removed, making it more difficult for patients to breathe. cardiovascular problems are also of concern. Low blood pressure ( hypotension) can occur because of blood loss or from blood pooling in the veins which dilate as body temperature is restored to normal. High blood pressure ( hypertension) may be due to pain, pre-existing hypertension, and an increased concentration of carbon dioxide in the blood or from having a full bladder. Common but less life-threatening problems include pain, nausea and vomiting. Usually your anaesthetist will leave orders for painkillers or analgesics, drugs to combat nausea and vomiting (anti-emetics), and intravenous fluids. These orders may be written after consultation with your surgeon, but your anaesthetist is the doctor in charge of your care in the Recovery Room.

What will I see ?

At first your vision is likely to be somewhat blurred. It is not uncommon to see more than one nurse or anaesthetist, despite the fact that only one is present at your bedside! Gradually you will be able to focus better. Although it is reassuring to be able to see clearly, many hospitals do not recommend that you take your glasses with you to the Operating Room. (This is because of the possibility that they might be mislaid or dropped while you were unconscious.) In that case, you would not be able to wear your glasses until you returned to the ward. Some hospitals do allow you to keep your spectacles with you.

If the hospital allows your relatives to be with you in the Recovery Room, it may be best to leave your spectacles with them. (Some hospitals do not allow any visitors in the Recovery Room.) If your child normally wears glasses, then it is a good idea to have them available, so that the Recovery Room nurse can give them to your child as he or she awakens.

What will I hear ?

In general, your hearing will not be significantly affected, although you may well forget instructions that are given to you during the early recovery period. Some people complain that sounds are louder than normal, but this is usually only temporary and is due to complex interactions between the various anaesthetic drugs and your hearing mechanism. A few patients may develop sudden loss of hearing in one or both ears after an anaesthetic and operation. One reason for this problem is the effect of pressure from the nitrous oxide on the eardrum and Eustachian tube (inside the ear). These patients may complain of pain and / or clicking and popping in the ear, like that which occurs in an aeroplane when climbing or descending. Very rarely, the mechanism of the hearing loss cannot be explained and hearing may or may not recover. However, this complication is extremely rare.

If you normally wear a hearing aid, you may choose to leave it in during the operation. This can be helpful if you have significant hearing loss and are having your operation under regional anaesthesia, when you might need to hear what your anaesthetist is saying to you. Other patients might choose not to wear their aids, especially if they fit loosely and do not provide good hearing. Some patients would prefer not to hear anything that goes on in the Operating Room or the Recovery Room and therefore leave the aids at their bedside.

What will I say ?

You may say all sorts of things, mostly related to your sense of disorientation or your surprise at being awake so soon. You may refer to pain or other discomfort, which can then be treated appropriately. Occasionally, patients say suggestive things to their medical or nursing staff, because the effect of the drugs is to temporarily remove some inhibitions. This is very uncommon, and if it does occur, it is always treated with discretion. This type of reaction lasts only a brief time and patients have no memory of the event. If relatives are present, they should not be concerned.

Will I be in pain ?

Your anaesthetist endeavours to ensure that you are as pain-free as possible at the end of your operation or procedure. This is not always easy to achieve. Some of the anaesthetic drugs provide some pain relief, but need to be stopped at the end of the anaesthetic so that you regain consciousness. A number of techniques are used to control postoperative pain, most being started during the anaesthetic. These techniques can be modified as necessary in the early postoperative phase in the Recovery Room, so that you have the maximum possible comfort. With some conditions, however, complete obliteration of pain may not be possible without risk of complications, especially where control of breathing may be affected.

Will I feel sick ?

You may feel nauseated and it is not uncommon for patients to vomit or ‘dry retch’ once or twice in the Recovery Room. Often this will bring up some mucous or bile-stained fluid, and is usually the only time that vomiting occurs, although some nausea may continue. Your anaesthetist may have given you some anti-emetic drugs during the anaesthetic if vomiting is thought likely to be a problem. Even if an anti-emetic has not already been given, it is not too late to administer some in the Recovery Room, and the nurse will arrange for it to be given.

Will I be cold ?

You may feel cold, and shivering is not uncommon in the Recovery Room. This is due partly to the fact that anaesthesia decreases the body’s ability to maintain a normal temperature, resulting in loss of body heat. Shivering is also due to some of the anaesthetic drugs that ‘switch on’ the shivering mechanism in the recovery phase.

In recent years, much more attention has been paid to ensuring preservation of body heat during surgery so that postoperative shivering is now less common. Devices such as warm water mattresses, warm air blankets, insulation wraps, and warmers for intravenous fluids and anaesthetic gases have contributed to this improvement.

Children in the Post-Anaesthesia Care Unit (PACU)

Children often go through a period of disorientation and restlessness which may be difficult to manage for a short time as they regain consciousness. This affects younger children more frequently and is quite normal, although rather distressing to parents or guardians. The reaction is more common after short procedures where there is minimal use of potent painkillers or other sedatives. The restlessness may be prevented or treated by the use of sedatives, either at the time or given as premedication. However, the effect of any of these drugs is to prolong recovery time significantly. If this type of distress has been a concern on previous occasions or with siblings, you should discuss the management with your child’s anaesthetist.

Children are frequently able to drink while still in the recovery room. Usually babies can be breast-fed, unless there is some particular reason to not do so.

In most modern surgical suites it is usual to allow parents to sit with their children as they awaken from anaesthesia. You may be encouraged to do so, once the nurse caring for your child is satisfied that all vital signs are stable and recovery is proceeding normally. You should ask your hospital or anaesthetist as to whether or not they allow this practice.

Some young children do not wake easily after an anaesthetic, especially if the anaesthetic coincides with the child’s normal sleep pattern. This is more likely if the recovery phase coincides with the child’s usual bedtime and if the child is normally a heavy sleeper. The situation may be quite disturbing to parents, but is quite normal. The use of painful stimulation to ‘wake the child up’ is discouraged.

Discharge from Post-Anaesthesia Care Unit (PACU)

Anaesthetists and nurses use specific criteria to determine if a patient is fit enough to be discharged from the recovery room. A patient must:

  • be able to breathe properly without assistance
  • have stable vital signs (for example, blood pressure and heart rate)
  • be awake (except children, see separate section) and orientated

If there is any bleeding from the surgical site, it should be well controlled and minimal.

In general, when a patient meets all these criteria, the nurse may discharge the patient from the Recovery Room without the anaesthetist being present. However, some patients require review by their anaesthetist, even if they meet the discharge criteria. Other patients might not meet the criteria, despite having spent what appears to be an appropriate length of time in the Recovery Room. This might be because of complications from the operation or anaesthetic, or from problems with pre-existing conditions. These patients might require further consultation (e.g. by a cardiologist or referral to an HDC or ICU).

The nurses are responsible for maintaining a record of the patient’s condition in the Recovery Room. They are also responsible for conveying relevant information to the ward, unit or clinic to which the patient is to be transferred. Depending on the operation, most patients stay for a minimum of 30 minutes in the Recovery Room, although this time may be increased to a few hours if the patient has undergone a very complex operation. Occasionally patients may have to stay longer in the Recovery Room, although they are ready for discharge because of administrative problems within the hospital, such as a lack of nurses or porters to transport the patient, or a lack of beds on the ward.

Back on the ward

After discharge from the recovery room, you are transported to a ward. This may be a regular ward, where you will spend at least one night. The length of time spend in the hospital ward varies according to the severity and length of your operation, and to a certain extent the complexity of anaesthesia.

Alternatively, you may be taken to a day ward, where you spend only a few hours before going home. Many procedures (up to 70 per cent in some countries) are now performed on a day-stay basis, with the patient staying in the hospital or clinic for less than 24 hours. Not all procedures are suitable for discharge home so soon, especially major operations involving surgery on the brain, or within the chest or abdominal cavities, or surgery requiring continuous intravenous or epidural pain relief, such as after total hip replacement.

No matter how long you stay, the nurses will ensure that you are continuing to follow the expected course of recovery from your anaesthetic and operation.

Postoperative pain relief

The management of postoperative pain is a continuation of the pain control provided during your anaesthetic. Both your anaesthetist and your surgeon may be involved in prescribing the drugs used for relieving your pain.

There are several options for postoperative pain control, which can be distinguished by the route or manner by which these drugs are given. These options include the following.

  • Oral or rectal analgesics and anti-inflammatory drugs

These drugs include paracetamol or acetaminophen (alone and with codeine), codeine phosphate, anileridine, tramadol, buprenorphine, indomethacin, and ketorolac. Most of them are taken as tablets, although a syrup may be used for children. Many of these drugs may also be given as suppositories. They are used for mild to moderate pain and are suitable for patients who are staying in hospital after minor operations or who are to be discharged home the day of the operation. These drugs have few common side effects, apart from constipation with codeine and the risk of reduced breathing if an overdose of anileridine is taken. There have been a few rare cases of sudden onset of kidney failure in patients who have been given ketorolac, although the evidence proving such a link is not clear.

  • Intramuscular injections

Most often this route is used for the administration of opiate or narcotic analgesics. These are given on an intermittent basis, usually every few hours. A typical order would be ‘ morphine 10 mg im q4h prn’ (which translates to ‘give 10 mg of morphine intramuscularly every four hours – but no sooner – if the patient wishes it’). This technique provides adequate, but not very good, pain control. Shortly after receiving the injection, the patient gets the effect of a large amount of drug, which may reduce breathing and produce sedation and even confusion. Then the effect of the drug wears off, leaving the patient in pain until the next injection. The use of intramuscular injections is declining in popularity, not only because continuous administration methods provide better pain control, but also because of the discomfort of the injection.

  • Continuous intravenous infusion

With this technique, opiates or narcotics are delivered directly via an intravenous cannula at a predetermined rate. This provides a steady concentration of drug in the bloodstream (in contrast to the intramuscular technique which gives a variable blood concentration). Nursing or medical staff may adjust the rate of infusion, according to the pain relief obtained.

  • Continuous subcutaneous infusion of analgesics

This is similar to the intravenous method, except that the fluid is pumped through a fine needle into the tissues just under the skin, usually on the abdomen. Because the volume of fluid is small, there is little swelling or discomfort and the drug is well absorbed.

  • Patient controlled analgesia (PCA)

This is another method of intravenous injection of opiates or narcotics, except that the patient controls the analgesia by pushing a button to determine when the injection is given. The administration of the drug is determined by a pump that has been programmed to deliver a fixed, safe dose of drug every time the patient requests it. There is a maximum hourly dose and a ‘lock-out’ interval that can be adjusted to prevent overdose. (This is similar to bank machines, which have limits on withdrawals.)

This technique is based on the principle that if the patient who has become sleepy will not push the button until the effect of the drug wears off. Of course, this principle requires that only the patient, and not a friend or family member, pushes the PCA button. Often anaesthetists are in charge of programming these pumps, although surgeons or specially trained nurses may also do so. If necessary, the dose and timing of the drug may be adjusted by reprogramming. Drugs commonly administered by this method include morphine, pethidine ( meperidine), and fentanyl. Some doctors also prescribe a constant infusion (or a ‘background infusion’) of a small amount of drug, so that there is always some pain relief present. However, this technique carries a greater risk of reduction of breathing, than does the ‘demand’ technique alone, although it is useful in certain patients with extreme pain.

  • Spinal narcotic injection

Some anaesthetists like to add a small amount of an opiate or narcotic when they inject local anaesthetic into the spinal at the time of the operation. This can provide very good pain relief. For example, a woman having a caesarean section might not need any other pain medication after the operation if she has received some spinal (‘intrathecal’) opiate or narcotic.

  • Spinal or epidural infusions

Continuous infusions of local anaesthetics and/or narcotic analgesics into the spinal fluid or epidural space may be given for several days after surgery. The advantage with this technique is that there is little sedation, compared with other methods. These methods are particularly useful for patients undergoing chest operations (thoracotomies) or upper abdominal operations, or major orthopaedic surgery to the hips and legs. These operations are painful and most patients require large amounts of intramuscular opiates or narcotics to provide adequate pain relief, with the possible risk of reduced breathing. The use of an epidural or spinal means that the patient can actually be pain-free.

  • Nerve blocks

In addition to general anaesthesia, some anaesthetists like to perform a nerve block – to provide analgesia (pain relief) of the area in which the operation or procedure is to take place. This is commonly done for children undergoing circumcision (with a penile nerve block) or hernia repair (with a caudal anaesthetic). Some anaesthetists believe that blocking pain nerves before the patient has any pain actually decreases the amount of pain relief required. This is termed ‘pre-emptive analgesia’.

Two other important points must be made about pain management. The first is the role of the acute pain Service (APS). In the 1970s, researchers began to investigate different methods for the relief of postoperative pain. Then in the 1980s, anaesthetists started to apply this knowledge to improve pain relief. These methods included all those described above. Use of these different techniques has varied widely between institutions; however, most large anaesthetic departments provide a postoperative analgesia service (or Acute Pain Service). Successful programmes rely on the assistance of dedicated, specially trained nursing support.

The other important point about pain management is that all patients who receive opiates or narcotics are at risk of reduced breathing. Some patients need to be looked after in special care units, not only because of the narcotics but for other medical or surgical reasons. Other patients require frequent monitoring, but can be cared for with regular nursing.

Are there other methods of pain relief ?

There are other methods of pain relief that do not involve the administration of drugs. These ‘non-pharmacological’ methods include:

  • Application of warmth: Heated gel or beanbag pads may be used, as may infrared lamps. Great care must be taken to avoid burning the skin, especially in the elderly and those with fragile skin or poor circulation. Lamps, in particular, should only be used for a short time.
  • Distraction: This is a method of pain relief which is useful in patients of all ages, but particularly in children. The idea is to concentrate the mind on something other than the pain. This can be done by reading, doing puzzles, story-telling, looking out a window at a busy street, and even watching television.
  • Relaxation: Three ways of relaxing and reducing the psychological awareness of pain are listening to music, meditating, and having a massage.

Anesthesia risks

Anesthesia today is safer than in the past, complications do occur. In very rare cases, anesthesia can cause complications (such as strange heart rhythms, breathing problems, allergic reactions to medications, and even death). One large study showed that about 10 per cent of patients experienced some problem during or after the anaesthetic. The complication could be as major as brain damage (but extremely rare) or as minor as muscle soreness (but more common). The most frequent complications are nausea, vomiting and sore throat. Anaesthetists are trained to recognise and manage complications quickly, and many will undergo part of this emergency training in simulators, much like airline pilots do.

The likelihood of a complication occurring is proportional to a variety of factors related to the patient’s health, the kind of procedure (complexity of the surgery being performed) and the type of anesthesia used. Be sure to talk to your doctor, surgeon, and/or anesthesiologist about any concerns.

The accompanying lists describe some of the complications that may occur during or after an anaesthetic. This lists are selective and do not include all complications.

Most complications can be prevented by giving the anesthesiologist complete information before the surgery about things like:

  • your current and past health (including diseases or conditions such as recent or current colds, or other issues such as snoring or depression)
  • any medications (prescription and over-the-counter), supplements, or herbal remedies you are taking
  • any allergies (especially to foods, medications, or latex) you may have
  • whether you smoke, drink alcohol, or take any recreational drugs
  • any previous reactions you or any family member has had to anesthesia

To ensure your safety during the surgery or procedure, it’s extremely important to answer all of the anesthesiologist’s questions as honestly and thoroughly as possible. Things that may seem harmless could affect how you react to the anesthesia.

It’s also important that you follow the doctor’s recommendations about what not to do before the surgery. You probably won’t be able to eat or drink (usually nothing after midnight the day before) and may need to stop taking herbal supplements or other medications for a certain period of time before surgery.

You can rest assured that the safety of anesthetic procedures has improved a lot over the years, thanks to advances in technology and the extensive training anesthesiologists receive. The more informed, calm, and reassured you are about the surgery and the safety of anesthesia, the easier the experience will probably be.

Anesthesia side effects

Common Side Effects of Anesthesia

You will most likely feel disoriented, groggy, and a little confused when waking up after surgery. Some other common side effects, which should go away fairly quickly, include:

  • nausea or vomiting, which can usually be alleviated with anti-nausea medication
  • chills or shakiness
  • sore throat (if a tube was used to help with breathing)

Complications during anaesthesia


Allergy to anaesthetic drugs is rare. The severity of allergic responses can range from mild (wheeze and rash) to severe (life-threatening anaphylactic reactions). As well as anaphylactic or immune-related reactions, some patients develop anaphylactoid reactions. Although this type of reaction does not involve antibodies, these reactions may also be severe, through the release of histamine.

If a patient is undergoing a general anaesthetic and is unconscious, the signs of an anaphylactic reaction may vary. The diagnosis is made by the recognition of such things as low blood pressure, wheezing, hives, rash, swelling (oedema) around the eyes or in the mouth and throat, and breathing difficulties.

Anaesthetists are trained to recognise and treat allergic reactions in the Operating Room. However, an important part of treatment of any allergic reaction is prevention. If you have any history of swelling of the face or generalised itching, you should let your anaesthetist know. Skin testing can be used to identify allergens (substances that cause allergic reactions). This may be helpful in identifying the particular drugs causing a reaction in those patients who apparently are ‘allergic to anaesthesia’.

The prevention of latex allergy includes removing all latex containing materials from the Operating Room, where possible. Most Operating Rooms have a special equipment kit for use in caring for latex-allergic patients.

Adverse drug reactions

Some patients may react abnormally to one or more drugs used during anaesthesia. Usually there will be some warning of this from prior experience, or knowledge of the particular condition or health of the patient. Occasionally, however, there is little warning, and the anaesthetist must be constantly alert to the potential for abnormal reactions.

Some patients develop complications because of the interaction of specific anaesthetic drugs with a pre-existing condition. There are very few ‘anaesthetic diseases’, that is, specific diseases for which anaesthetic drugs must be carefully selected so as to minimise the risk of problems. However, these diseases do exist. The following brief description of two of these conditions is not meant to replace a more definitive source of information.

Malignant hyperthermia or malignant hyperpyrexia

Malignant hyperthermia or malignant hyperpyrexia consists of an unexplained rise in body temperature and muscle rigidity during anaesthesia, due to a massive increase in metabolism. Consumption of oxygen and production of carbon dioxide also rise markedly. Predisposition to malignant hyperthermia is an inherited condition and occurs in about 1 in 40,000 patients. Malignant hyperpyrexia is triggered after exposure to specific anaesthetic drugs – the volatile anaesthetic agents (such as isoflurane) and suxamethonium. Triggering may occur on the first exposure to these drugs or even after repeated and uncomplicated anaesthetics.

Treatment of an episode of malignant hyperpyrexia consists of stopping the triggering drug, stopping the operation if possible, and administering a drug called dantrolene. This is the only specific drug treatment for this syndrome; without it, about half of all patients who suffer a malignant hyperthermia reaction will die. Other treatment is also important, in the form of extra oxygen, cooling, and resuscitative drugs and fluids.

The principal test for malignant hyperpyrexia is one performed on a piece of biopsied muscle, although unfortunately some tests appear to show that the patient has the condition when in fact the patient does not. (This is known as a ‘false positive’ test result.) As more genetic patterns are recognised in families with malignant hyperpyrexia, some susceptible patients may be diagnosed using genetic marking. The patient and close relatives should all be tested. A patient who has had an malignant hyperpyrexia reaction or a positive test should obtain some form of Medic Alert notification and carry this at all times.

If a patient with known malignant hyperpyrexia requires an operation, then the Operating Room should be specially prepared. No volatile anaesthetic agents should be used in the room for 12 hours and, if possible, the patient should be scheduled as the first case of the day. A ‘safe’ technique consists of avoiding the known triggering agents and is not difficult to achieve. Drugs that are considered ‘safe’ include nitrous oxide, thiopentone, propofol, midazolam, narcotics, muscle relaxants such as curare or vecuroniun, and any of the local anaesthetic drugs. The patient’s condition, including temperature, should be carefully monitored as with any general anaesthetic. This monitoring should continue into the postoperative period. Some patients have been reported to have a reaction after a ‘safe’ anaesthetic, but these reactions apparently have not been severe.

Plasma cholinesterase deficiency

Plasma cholinesterase deficiency or pseudocholinesterase deficiency (PChD) is an enzyme deficiency that affects the metabolism of some anaesthetic drugs, thus lengthening their action. These drugs include certain types of local anaesthetic agents and suxamethonium. It is important to remember that having PChD does not mean that the patient is ‘allergic’ to these drugs, but simply that the drug takes longer to wear off.

If a patient with PChD is given suxamethonium, then the muscle relaxation from the drug may last for several hours, instead of a few minutes. During this time, the patient is unable to move or breathe spontaneously, and requires artificial ventilation. sedation, which makes the period of the profound weakness less unpleasant, is used while the action of the drug wears off.

PChD may be inherited and is found in less than 0.01 per cent of the population. The condition may also occur in patients with liver failure and certain tumours, as well as in those exposed to specific drugs, such as ecothiopate, and to certain insecticides. Some women at the end of pregnancy may develop a very mild form of PChD which disappears after birth of the baby. The enzyme deficiency can be confirmed by a special blood test.

Heart attack or stroke

It is possible to suffer a heart attack during the course of an anaesthetic. However, if one does occur, it is more likely to be on the second or third day after the operation. The risk of having a heart attack or myocardial infarction (MI) is very low, but patients who have suffered an MI in the past should consider not having elective surgery during the following six months.

Other patients with severe hardening of the arteries of the neck (carotids) are not only at risk of myocardial infarction, but also of a stroke (cerebro-vascular accident or CVA). Again, this is a rare but serious complication of anaesthesia.

Obstructed breathing

  • Laryngospasm

Sometimes, especially at the beginning or end of an anaesthetic, the vocal chords in the larynx (voice box) may close, making it very difficult for any air or oxygen to pass to and from the lungs. The condition can be likened to “choking”, and if allowed to continue, can result in a lack of oxygen entering the bloodstream. Anaesthetists are trained to deal effectively with this potentially serious complication, sometimes requiring the emergency administration of drugs to relax all muscles.

  • Difficult airway

Some patients have particular anatomical features of their neck and mouth that make management of their airway, or intubation difficult. The anaesthetist will make a judgement as to the likelihood of such a problem, during the pre-anaesthetic assessment. If he or she suspects that there may be a difficult airway, the anaesthetist will ensure that additional specialised equipment and expert assistance is immediately available.

  • Bronchospasm

Bronchospasm refers to a narrowing of the major airway branches in the lung. The result is similar to severe asthma with wheezing. When it occurs, the flow of air is reduced, especially when breathing out (exhaling). Commonly, bronchospasm is easily treated by deepening the anaesthetic, removing the stimulus, or giving drugs such as salbutamol, aminophylline, or steroids. For particularly severe reactions, adrenaline may be required.

Patients with asthma or chronic obstructive lung disease (COPD) and smokers may develop wheezing or bronchospasm. Bronchospasm may also occur in previously healthy patients during an allergic reaction due to drugs or blood products or after aspiration of gastric contents. Bronchospasm may also occur after such procedures as insertion of the breathing tube.

  • Pneumothorax

In this condition, air (or another gas) enters the normally empty space between the lungs and the chest wall. If not detected and treated, this can be life threatening as the gas expands and compresses the heart and the major blood vessels in the chest, preventing blood from entering or leaving. Most often a patient has a small but undiagnosed leak in the lining of the lung. This leak increases with the use of artificial ventilation. The problem may occur spontaneously in those with congenital swellings (bullae) of the lungs, patients with chronic lung disease and emphysema, or in asthmatics. In addition, the lining of the lung may be accidentally punctured by some injections around the neck or in the chest region.

Complications after anaesthesia

Nausea and vomiting

Postoperative nausea and vomiting is one of the most common postoperative complications, affecting up to as many as 40 per cent of patients. The patient most likely to vomit is a young, non-smoking, overweight woman who has undergone gynaecological surgery. Also at risk are patients with a history of postoperative nausea and vomiting and those with a history of motion sickness (in a car or aeroplane or at sea).

All anaesthetic agents have been blamed, with opiates or narcotics most often implicated. Indeed, the anaesthetic is most often blamed for all postoperative nausea and vomiting, even when nausea and vomiting occurs days after the operation and all traces of the anaesthetic have disappeared from the body.

Other factors may contribute, including:

  • preoperative conditions, such as vomiting, increased pressure in the brain, intoxication with alcohol or other drugs
  • operations on the eyes, the inner ear, the testicles, or tonsil
  • postoperative conditions, such as the presence of blood in the stomach (which no anti-emetic can counter) or blockage of the bowel
  • pain and anxiety
  • the presence of other vomiting patients or the smell of food
  • rapid movement (as on a stretcher) or even slight elevation of the head from the pillow
  • painkillers given during the anaesthetic or in the postoperative period.

Many of these factors can be avoided or treated, to reduce the chance of postoperative nausea and vomiting occurring. Your anaesthetist makes all attempts to ensure that you do not suffer from postoperative nausea and vomiting. However, complete prevention of this complication is not possible.

Dental damage

Although anaesthetists are very careful to avoid contact with the teeth, damage may occur when metal or hard plastic instruments are used to maintain an open airway, to help with insertion of the breathing ( endotracheal) tube, or to suck out secretions from the mouth and back of the throat. In most cases, damage occurs at the time of tracheal intubation, in about one in every 1000 intubations. Dental damage may also occur when a patient bites down on an oral airway during recovery from anaesthesia. The force generated is enough to break both natural and restored teeth and has been noted in between a quarter and a half of all reported cases of dental damage.

Although human teeth are very strong, they become more brittle with age. Just as you may chip a tooth while eating, the same may occur during intubation. Cosmetic dental work, with veneers, crowns or bridges, is a particular concern, as these structures are not as strong as natural teeth.

If you have had dental work, especially on your front teeth, then you should inform your anaesthetist and discus any concerns you might have. You should also point out any teeth which are loose. You may be able to lessen the risk of damage by having an alternative technique to general anaesthesia, such as regional anaesthesia (if appropriate). However, in some cases, general anaesthesia with an endotracheal tube is necessary. Attempting to avoid tracheal intubation, for example by using a mask, may lead to other complications, such as aspiration of stomach contents into the lungs. Some anaesthetists try to prevent dental damage by removing the oral airway before their patients regain consciousness and replacing it with a soft short tube placed in one nostril. (This is known as a nasal airway.)

Should any of your teeth be damaged or lost during an anaesthetic or operation, or while you are in the recovery room, you will need emergency treatment. This includes re-insertion of the tooth (if appropriate) and emergency dental consultation (if available). Great effort should be made to locate any missing teeth and you may need to have a chest X-ray to ensure that you have not inhaled the tooth. If you have and the tooth is not removed from your lung, then there is a high probability of pneumonia.

Similarly, children may undergo anaesthesia when their first teeth are about to be lost. These first teeth are very easily dislodged, and you should tell the anaesthetist which teeth are loose. Sometimes parents request the anaesthetist remove a tooth that is about to fall out!

Adults with loose teeth should see a dentist, if possible, before their anaesthetic. The same suggestion applies if any of the teeth are badly broken or decayed. In addition, professional dental cleaning is recommended for patients who have gum disease, especially for those patients who are scheduled to have a major operation.


Patients often develop a small bruise at the site of insertion of the intravenous cannula, in the back of the hand, in the forearm near the wrist, or in the bend of the elbow. These bruises can become painful and may take a week or so to resolve. Elderly patients, and those with fragile skin and veins, bruise more easily and the bruise often takes longer to disappear.

Eye problems

Various types of eye damage may occur. The cornea or surface of the eye may be scratched when the eyelids are not completely closed, particularly if the face is covered with drapes or towels. Some anaesthetists choose to secure the eyelids closed with tape – although certain patients may develop skin reactions and others may complain of loss of eyelashes after removal of the tape. Other anaesthetists choose to insert a lubricating ointment into the eye – although eye infections have been reported if the ointment is contaminated. Some patients have complained of blurring of vision for a few hours postoperatively, because of the residual ointment. However, corneal damage may occur even if the eye is lubricated and taped shut. The presence of make-up, such as mascara, is potentially hazardous.

Blindness after both general and regional anaesthesia is rare, but it can occur. Loss of vision may result from pressure on the eye. It may be that the arteries at the back of the eye (retina) become compressed, thus depriving the eye of oxygen. Smokers are more at risk than are nonsmokers, because nicotine constricts or narrows arteries, further depriving the eye and the brain of oxygen. Temporary blindness may also occur after spinal anaesthesia for resection of the prostate gland in men. This is due to the effect of a special chemical in the fluid placed in the bladder by the surgeon during the course of the operation.

Nerve damage

Almost any nerve can be damaged. Nerves of the face may be damaged by pressure from the anaesthetic breathing circuit or from the anaesthetist’s fingers holding the facemask on and the chin forward. The most common nerve injury is to the ulnar nerve at the elbow, from compression against a hard surface. In general, the prevention of nerve damage is by careful positioning and padding of the patient during anaesthesia. In the past, the cause of postoperative nerve damage was always thought due to improper positioning of the patient; however, some patients who develop nerve damage have been found to have a pre-existing problem.


Sometimes, instead of passing the breathing (endotracheal) tube through your mouth, your anaesthetist chooses to pass it into one nostril and down the back of the throat and into your voice box ( larynx). This change in route may still involve insertion of the laryngoscope into your mouth, so that your anaesthetist can see where he or she is placing the tube. Nasal intubation is normally used for operations around the face and mouth.

Insertion of the tube through the nostril often results in some bleeding from the nose after the tube is removed. This bleeding normally stops after a few minutes, although seeing the nose bleed may be distressing to family members.

Blood clots

Certain patients are at increased risk of having blood clots – for example, those taking oral contraceptives or hormone replacement. Certain surgical procedures also increase the risk of clots, such as operations that last several hours or are on the lower part of the body. In general, anaesthetics do not increase the risk of having a blood clot.

Brain damage

Some operations may lead to a decrease in intellectual ability, for example, after major brain or open heart surgery. Other patients are at risk because of pre-existing medical conditions, such as age-related loss of memory. Elderly patients, particularly those with progressive heart disease, high blood pressure or a history of minor strokes may suffer permanent changes after anaesthesia. This may be a result of a change in critical blood supply to certain parts of the brain, altering specific chemicals in the brain.

Blood supply to the brain may be subtly altered by a decrease in the amount of carbon dioxide in the blood and by slight changes in blood pressure. Many anaesthetic drugs have side effects which can alter blood flow, although modern drugs are less likely to produce these effects.

On rare occasions, patients have suffered brain damage due to lack of oxygen delivery to the brain. Even though all aspects of the anaesthetic are carefully monitored during an anaesthetic, sometimes problems can occur.

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