What Causes Dehydration ?

Dehydration is usually caused by not drinking enough fluid to replace what you lose. The climate, the amount of physical exercise you are doing (particularly in hot weather) and your diet can contribute to dehydration ⁸⁾. You can also become dehydrated as a result of an illness, such as persistent vomiting and diarrhea, or sweating from a fever.

• This is a 2 part series on the topic of dehydration. For part 1 please visit here: https://healthjade.com/symptoms-and-signs-dehydration/

Your body may lose a lot of fluid from:

• Sweating too much, for example, from exercising in hot weather
• Fever
• Vomiting or diarrhea
• Urinating too much (uncontrolled diabetes or some medications, like diuretics, can cause you to urinate a lot)

You might not drink enough fluids because:

• You do not feel like eating or drinking because you are sick
• You are nauseated
• You have a sore throat or mouth sores

Older adults and people with certain diseases, such as diabetes, are also at higher risk for dehydration.

Illness

• Diarrhea, vomiting. Severe, acute diarrhea — that is, diarrhea that comes on suddenly and violently — can cause a tremendous loss of water and electrolytes in a short amount of time. If you have vomiting along with diarrhea, you lose even more fluids and minerals.

• Fever. In general, the higher your fever, the more dehydrated you may become. The problem worsens if you have a fever in addition to diarrhea and vomiting.

Sweating

You can also become dehydrated if you sweat excessively after a fever, exercise, or carrying out heavy, manual work in hot and humid weather conditions.

In these situations, it’s important to drink regularly to replace lost fluids. It doesn’t necessarily need to be hot for you to lose a significant amount of fluid from sweating.

Children and teenagers are particularly at risk because they may ignore the symptoms of dehydration, or not know how to recognise and treat them.

Alcohol

Dehydration can also occur as a result of drinking too much alcohol. Alcohol is a diuretic, which means it makes you wee more.

The headache associated with a hangover indicates that your body is dehydrated. You should try to drink plenty of water when you have been drinking alcohol.

Diabetes

If you have diabetes, you’re at risk of becoming dehydrated because you have high levels of glucose in your bloodstream. Your kidneys will try to get rid of the glucose by creating more urine, so your body becomes dehydrated from going to the toilet more frequently.

Increased urination

This may be due to undiagnosed or uncontrolled diabetes. Certain medications, such as diuretics and some blood pressure medications, also can lead to dehydration, generally because they cause you to urinate more.

Who Is at Risk of Dehydration ?

Anyone can become dehydrated, but certain people are at greater risk:

• Infants and children. The most likely group to experience severe diarrhea and vomiting, infants and children are especially vulnerable to dehydration. Having a higher surface area to volume area, they also lose a higher proportion of their fluids from a high fever or burns. Young children often can’t tell you that they’re thirsty, nor can they get a drink for themselves.

• Older adults. As you age, your body’s fluid reserve becomes smaller, your ability to conserve water is reduced and your thirst sense becomes less acute. These problems are compounded by chronic illnesses such as diabetes and dementia, and by the use of certain medications. Older adults also may have mobility problems that limit their ability to obtain water for themselves.

• People with chronic illnesses. Having uncontrolled or untreated diabetes puts you at high risk of dehydration. Kidney disease also increases your risk, as do medications that increase urination. Even having a cold or sore throat makes you more susceptible to dehydration because you’re less likely to feel like eating or drinking when you’re sick.

• People who work or exercise outside. When it’s hot and humid, your risk of dehydration and heat illness increases. That’s because when the air is humid, sweat can’t evaporate and cool you as quickly as it normally does, and this can lead to an increased body temperature and the need for more fluids.

That’s why it’s important to increase water intake during hot weather or when you’re ill.

Dehydration in the Elderly

Elderly individuals have a higher risk of developing dehydration than do adults. Dehydration is the most common fluid and electrolyte problem among the elderly. The usual causes of water loss are frequently absent in dehydrated elderly patients. Age-related changes in total body water, thirst perception, renal concentrating ability, and vasopressin effectiveness probably predispose to dehydration ⁹⁾. Dehydration related to infection, high-protein tube feedings, cerebral vascular accidents (strokes) and medication-related hypodypsia are particularly relevant for elderly patients. Appropriate treatment depends on accurately assessing the water deficit and slowly correcting that deficit.

The diminution of the sensation of thirst ¹⁰⁾, the decreased renal ability to concentrate urine, the relative resistance of the kidney to ADH, the diminution of renin activity and the low secretion of aldosterone, all increase the risk of dehydration. In addition, the elderly may encounter difficulties in gaining access to drinks because of diminution of mobility, visual troubles, swallowing disorders, cognitive alterations and use of sedatives. Fear of incontinence may lead some elderly people to limit their liquid intake. Low dietary intake also decreases the water intake that is held in aliments and contributes to a water deficit. Medications such as diuretics or laxatives can enhance water loss.

The clinical signs of dehydration include neuropsychic symptoms such as mental confusion, impaired cognitive functions ¹¹⁾, mucosal dryness, hypotonia of ocular globes, orthostatic hypotension and tachycardia ¹²⁾. Loss of body water also increases the risk of hyperthermia under conditions of high ambient temperature ¹³⁾. The risk of falls, kidney stones and urinary infections are also increased in dehydrated elderly individuals ¹⁴⁾. However, from a recent review, there was sufficient evidence to suggest that several stand‐alone tests often used to assess dehydration in older people (including fluid intake, urine specific gravity, urine colour, urine volume, heart rate, dry mouth, feeling thirsty and BIA assessment of intracellular water or extracellular water) are not useful, and should not be relied on individually as ways of assessing presence or absence of dehydration in older people ¹⁵⁾.

This review ¹⁶⁾ showed only three tests offers any ability to diagnose water‐loss dehydration in the elderly (including both impending and current water‐loss dehydration) as stand‐alone tests:

• expressing fatigue (sensitivity 0.71 and specificity 0.75), in one study with 71 participants, but two additional studies had lower sensitivity);
• missing drinks between meals (sensitivity 1.00 and specificity 0.77), in one study with 71 participants) and
• Bioelectrical impedance analysis (BIA) is a commonly used method for estimating body composition, and in particular body fat. BIA resistance at 50 kHz (sensitivities 1.00 and specificities of 1.00) in 22 people from two studies, but with sensitivities of 0.50 and specificity of 0.19 in 1947 people in two other studies.
• Drinks intake, urine osmolality and axillial moisture also showed limited diagnostic accuracy. No test was consistently useful in more than one study.

Combining two tests so that an individual both missed some drinks between meals and expressed fatigue was sensitive at 0.71 and specific at 0.92 ¹⁷⁾.

Dehydration in Infants

Infants have a higher percentage of water (75% of body weight at birth) ¹⁸⁾ than do adults. Several factors make infants more vulnerable to fluid and electrolyte imbalance than adults: the high surface-to-body-weight ratio, the limited ability to excrete solutes and to concentrate urine, the low ability to express thirst and the high rate of metabolic rate ¹⁹⁾. Problems of hydration may occur in case of fever (which increases insensible water loss), vomiting, diarrhoea and the use of formula not diluted appropriately. The adequate water intake for infants aged 0–6 months is 0.7 l/day ²⁰⁾.

Dehydration in Children

More than half of all children and adolescents in the U.S. are not getting enough hydration—probably because they’re not drinking enough water—a situation that could have significant repercussions for their physical health and their cognitive and emotional functioning, according to the first national study of its kind from Harvard T.H. Chan School of Public Health ²¹⁾. The study also found racial/ethnic and gender gaps in hydration status. Black children and adolescents were at higher risk of inadequate hydration than whites; boys were at higher risk than girls.

The researchers found that a little more than half of all children and adolescents weren’t getting enough hydration. Boys were 76% more likely than girls, and non-Hispanic blacks were 34% more likely than non-Hispanic whites, to be inadequately hydrated ²²⁾.

More worrisome, nearly a quarter of the children and adolescents in the study reported drinking no plain water at all ²³⁾.

The following children are at increased risk of dehydration ²⁴⁾:

• Children younger than 1 year, particularly those younger than 6 months
• Infants who were of low birthweight
• Children who have passed more than five diarrhoeal stools in the previous 24 hours
• Children who have vomited more than twice in the previous 24 hours
• Children who have not been offered or have not been able to tolerate supplementary fluids before presentation
• Infants who have stopped breastfeeding during the illness
• Children with signs of malnutrition.

What are symptoms and signs of dehydration ?

Clinical symptoms and signs of dehydration generally have poor sensitivity and specificity ²⁵⁾. Nevertheless, factors that have a sensitivity >80% are dry mucous membranes in the mouth and nose and longitudinal furrows on the tongue. Some other factors have good specificity (>80%): speech incoherence, extremity weakness, dry axilla and sunken eyes.

Dehydration can be mild, moderate or severe, depending on how much of your body weight is lost through fluids ²⁶⁾. Signs of mild-to-moderate and severe dehydration are listed in Table 2 ²⁷⁾. More recently, it has been shown that mild dehydration corresponding to only 1–2% of body weight loss in adults can lead to a significant impairment in both cognitive function (alertness, concentration, short-term memory) and physical performance (endurance, sports skills) ²⁸⁾, ²⁹⁾. Populations at particular risk of dehydration include the very young and the elderly.

Two early signs of dehydration are thirst and dark-coloured urine. This is the body’s way of trying to increase water intake and decrease water loss. However, thirst isn’t always a reliable early indicator of the body’s need for water. Many people, particularly older adults, don’t feel thirsty until they’re already dehydrated. From a recent dehydration in the elderly review ³⁰⁾ only two tests showed any ability to diagnose water‐loss dehydration in the elderly (including both impending and current water‐loss dehydration) as stand‐alone tests. expressing fatigue and missing drinks between meals were shown to be sensitive and specific to diagnose dehydration in the elderly. Furthermore, fluid intake, urine specific gravity, urine color, urine volume, heart rate, dry mouth, feeling thirsty and bioelectrical impedance analysis (BIA) assessment of intracellular water or extracellular water are not useful, and should not be relied on individually as ways of assessing presence or absence of dehydration in older people ³¹⁾.

Heat- and exercise-induced moderate acute dehydration resulted in a significant impairment of specific cognitive-motor functions such as short-term memory, working memory, perceptive discrimination, and visual-motor function ³²⁾, ³³⁾. The critical level of acute water deficit causing a decrease in cognitive performance occurred at a level of 2% or more ³⁴⁾. Adverse effects of acute moderate dehydration induced by heat or exercise were identical ³⁵⁾.

In contrast, reduced drinking in the presence of physiological needs may be particularly important in predisposing to subacute and chronic dehydration in the general population ³⁶⁾, ³⁷⁾. Water deprivation for 24 hours can induce a comparable level of water deficit, as acute heat or exercise testing during 0.5–2 hours ³⁸⁾, ³⁹⁾.

That’s why it’s important to increase water intake during hot weather or when you’re ill.

Table 1. Signs of dehydration in Adults

Some of the early warning signs of dehydration in adults include ⁴¹⁾, ⁴²⁾, ⁴³⁾:

• A dry mouth, lips and eyes
• Feeling thirsty and lightheaded
• Urinating less often than usual (less than three or four times a day)
• Passing small amounts of urine infrequently
• Dark-colored urine, strong-smelling urine
• Dry cool skin
• Feeling tired
• Headache
• Confusion
• Muscle cramps
• Dizziness, light-headedness and fainting.

Signs of severe dehydration in adults ⁴⁴⁾:

• Not urinating, or very dark yellow or amber-colored urine
• Dry, shriveled skin
• Irritability or confusion
• Dizziness or light-headedness
• Rapid heartbeat
• Rapid breathing
• Sunken eyes
• Listlessness
• Shock (not enough blood flow through the body)
• Unconsciousness or delirium

Dehydration can also lead to a loss of strength and stamina. It’s a main cause of heat exhaustion.

The body is affected even when you lose a small amount of fluid.

You should be able to reverse dehydration at this stage by drinking more fluids.

If dehydration is ongoing (chronic), it can affect your kidney function and increase the risk of kidney stones. It can also lead to muscle damage and constipation.

A baby or a young child may be dehydrated if they ⁴⁵⁾, ⁴⁶⁾, ⁴⁷⁾:

• have a sunken soft spot (fontanelle) on their head
• dry mouth and tongue
• sunken eyes, cheeks
• Listlessness or irritability
• no wet diapers for 3 hours or more
• have few or no tears when crying
• have fewer wet nappies (nappies will feel lighter)
• are drowsy
• a high fever
• unusually sleepy or drowsy.

Table 1. Symptoms and signs of clinical dehydration and shock in Children (Under 5 years)

Increasing severity of dehydration
	No clinically detectable dehydration	Clinical dehydration	Clinical shock
Symptoms (remote and face-to-face assessments)	Appears well	Appears to be unwell or deteriorating	–
	Alert and responsive	Altered responsiveness (for example, irritable, lethargic)	Decreased level of consciousness
	Normal urine output	Decreased urine output	–
	Skin colour unchanged	Skin colour unchanged	Pale or mottled skin
	Warm extremities	Warm extremities	Cold extremities
Signs (face-to-face assessments)	Alert and responsive	Altered responsiveness (for example, irritable, lethargic)	Decreased level of consciousness
	Skin colour unchanged	Skin colour unchanged	Pale or mottled skin
	Warm extremities	Warm extremities	Cold extremities
	Eyes not sunken	Sunken eyes	–
	Moist mucous membranes (except after a drink)	Dry mucous membranes (except for ‘mouth breather’)	–
	Normal heart rate	Tachycardia	Tachycardia
	Normal breathing pattern	Tachypnoea	Tachypnoea
	Normal peripheral pulses	Normal peripheral pulses	Weak peripheral pulses
	Normal capillary refill time	Normal capillary refill time	Prolonged capillary refill time
	Normal skin turgor	Reduced skin turgor	–
	Normal blood pressure	Normal blood pressure	Hypotension (decompensated shock)

Patients would merely be classified as follows: ‘no clinically detectable dehydration’, ‘clinical dehydration’ and ‘clinical shock’. With this assessment scheme the clinician would have to recognise the presence of clinical dehydration. This simplified scheme does not imply that the degree of dehydration is uniform, but rather acknowledges the difficulties in accurately assessing dehydration severity. The Guideline Development Group ⁴⁹⁾ recognised that experienced clinicians could distinguish marked differences in the severity of dehydration. They also considered that clinical signs were likely to be more pronounced and numerous in those with severe dehydration. However, firm recommendations linking clinical symptoms and signs with specific varying levels of dehydration were impossible. The crucial point however, is that the scheme (Table 3) is all that is required to guide fluid management ⁵⁰⁾.

Diagnosis of dehydration

Your doctor can often diagnose dehydration on the basis of physical signs and symptoms. If you’re dehydrated, you’re also likely to have low blood pressure, especially when moving from a lying to a standing position, a faster than normal heart rate and reduced blood flow to your extremities.

To help confirm the diagnosis and pinpoint the degree of dehydration, you may have other tests, such as:

• Blood tests. Blood samples may be used to check for a number of factors, such as the levels of your electrolytes — especially sodium and potassium — and how well your kidneys are working.
• Urinalysis. Tests done on your urine can help show whether you’re dehydrated and to what degree. They also can check for signs of a bladder infection.

In Infants and Children

In general, dehydration is defined as follows ⁵¹⁾:

• Mild: No hemodynamic changes (about 5% body wt in infants and 3% in adolescents)
• Moderate: Tachycardia (about 10% body wt in infants and 6% in adolescents)
• Severe: Hypotension with impaired perfusion (about 15% body wt in infants and 9% in adolescents)

However, using a combination of symptoms and signs to assess dehydration is a more accurate method than using only one sign. Another way to assess the degree of dehydration in children with acute dehydration is change in body weight; all short-term weight loss > 1%/day is presumed to represent fluid deficit. However, this method depends on knowing a precise, recent preillness weight. Parental estimates are usually inadequate; a 1kg error in a 10kg child causes a 10% error in the calculated percentage of dehydration—the difference between mild and severe dehydration ⁵²⁾.

Laboratory testing is usually reserved for moderately or severely ill children, in whom electrolyte disturbances (eg, hypernatremia, hypokalemia, metabolic acidosis or alkalosis) are more common, and for children who need IV fluid therapy. Other laboratory abnormalities in dehydration include relative polycythemia resulting from hemoconcentration, elevated blood urea nitrogen, and increased urine specific gravity.

Evidence from a single prospective study indicated that hypernatraemia was more common in young infants (<6 months) with diarrhoea ⁵³⁾. Children with hypernatraemic dehydration had an increased frequency of symptoms of central nervous system dysfunction. Using clinical assessment, the severity of dehydration was more often underestimated in hypernatraemic dehydration than in children with dehydration associated with a normal plasma sodium concentration.

Suspect hypernatraemic dehydration if there are any of the following ⁵⁴⁾:

• jittery movements
• increased muscle tone
• hyperreflexia
• convulsions
• drowsiness or coma.

Dehydration Treatment

• Children and adults who are severely dehydrated should be treated by emergency personnel arriving in an ambulance or in a hospital emergency room. Salts and fluids delivered through a vein (intravenously) are absorbed quickly and speed recovery.

Example in Hospital Emergency Room

A 7-mo-old infant has diarrhea for 3 days with weight loss from 10 kg to 9 kg. The infant is currently producing 1 diarrheal stool every 3 h and refusing to drink. Clinical findings of dry mucous membranes, poor skin turgor, markedly decreased urine output, and tachycardia with normal BP and capillary refill suggest 10% fluid deficit. Rectal temperature is 37° C; serum Na, 136 mEq/L; K, 4 mEq/L; Cl, 104 mEq/L; and HCO3, 20 mEq/L.

Fluid volume is estimated by deficits, ongoing losses, and maintenance requirements.

• The total fluid deficit given 1 kg wt loss = 1 L.
• Ongoing diarrheal losses are measured as they occur by weighing the infant’s diaper before application and after the diarrheal stool.
• Baseline maintenance requirements by the weight-based Holliday-Segar method are 100 mL/kg × 10 kg = 1000 mL/day = 1000/24 or 40 mL/h.

Electrolyte losses resulting from diarrhea in a eunatremic patient are an estimated 80 mEq of Na and 80 mEq of K.

IV Fluid Resuscitation

The patient is given an initial bolus of lactated Ringer solution 200 mL (20 mL/kg × 10 kg) over 30 min. This amount replaces 26 mEq of the estimated 80 mEq Na (sodium) deficit.

Deficits

• Residual fluid deficit is 800 mL (1000 initial − 200 mL resuscitation), and Na deficit is 54 mEq (80 − 26 mEq). This residual amount is given over the next 24 h. Typically, half (400 mL) is given over the first 8 h (400 ÷ 8 = 50 mL/h) and the other half is given over the next 16 h (25 mL/h). The fluid used is 5% dextrose/0.45% saline. This amount replaces the Na deficit (0.8 L × 77 mEq Na/L =62 mEq Na). When urine output is established, K is added at a concentration of 20 mEq/L (for safety reasons, no attempt is made to replace complete K deficit acutely).

Ongoing losses

Five percent dextrose/0.45% saline also is used to replace ongoing losses; volume and rate are determined by the amount of diarrhea.

Switch from intravenous hydration to oral rehydration solution once hydration is improved and the patient can drink. This will conserve IV fluids and reduce the risk of phlebitis and other complications.

Nasogastric tubes can be used to administer oral rehydration solution if patient is alert but unable to drink sufficient quantities independently.

Maintenance fluid

Five percent dextrose/0.2% or 0.45% saline is given at 40 mL/h with 20 mEq/L of K added when urine output is established. Alternatively, the deficit could be replaced during the initial 8 h followed by the entire day’s maintenance fluid in the next 16 h (ie, 60 mL/h); 24 h of maintenance fluid given in 16 h reduces mathematically to a rate of 1.5 times the usual maintenance rate and obviates the need for simultaneous infusions (which may require 2 rate-controlling pumps).

World Health Organization (WHO) Fluid Replacement or Treatment Recommendations

*Repeat once if radial pulse is still very weak or not detectable

Treatment of Dehydration at Home

A well-conducted systematic review did not find any significant difference in the incidences of hyponatraemia, hypernatraemia, the mean duration of diarrhoea, weight gain or total fluid intake in children treated with oral rehydration solution therapy compared with intravenous therapy ⁵⁶⁾. Although oral rehydration solution therapy was associated with a 4% higher risk of rehydration failure, when the analysis was conducted using a homogeneous definition of rehydration failure, no statistically significant difference was seen. Dehydrated children treated with oral rehydration solution therapy had a significantly shorter stay in hospital and those receiving intravenous therapy had a higher risk of phlebitis (vein inflammation) but no statistically significant differences were found between the oral rehydration solution therapy and intravenous therapy groups for the other complications – hypernatraemia, paralytic ileus, abdominal distension, peri-orbital oedema or seizures ⁵⁷⁾. Methodologically, there was great variation between the trials with regard to the study population characteristics, composition of oral rehydration solution solution and the modes of administration of oral rehydration solution solution.

The only effective treatment for dehydration is to replace lost fluids and lost electrolytes. The best approach to dehydration treatment depends on age, the severity of dehydration and its cause.

• Oral rehydration solution should contain complex carbohydrate or 2% glucose and 50 to 90 mEq/L of Na ⁵⁸⁾. Sports drinks, sodas, juices, and similar drinks do not meet these criteria and should not be used. They generally have too little Na and too much carbohydrate to take advantage of Na/glucose cotransport, and the osmotic effect of the excess carbohydrate may result in additional fluid loss. The Na/glucose cotransport in the gut is optimized with an Na:glucose ratio of 1:1.

Oral rehydration solution is recommended by the World Health Organization and is widely available in the US without prescription. Most solutions come as powders that are mixed with tap water.

An oral rehydration solution packet is dissolved in 1 Liter of water to produce a solution containing glucose 111, sodium 90, potassium 20, chloride 80 and bicarbonate 30, all in 311 mmol/l (standard WHO ORS with high 311 mmol/l with sodium:glucose ratio 1:3) ⁵⁹⁾ or sodium 75, potassium 20, chloride 65, citrate 10, and glucose 75 (WHO reduced-osmolarity ORS with 245 mmol/l low sodium:glucose ratio 1:1) ⁶⁰⁾. There is evidence from one high-quality systematic review indicating a significant reduction in the need for unscheduled IV fluids for the treatment of dehydration in children with diarrhoea when using low-osmolarity ORS solution (sodium 75, potassium 20, chloride 65, citrate 10, and glucose 75 (WHO reduced-osmolarity ORS with 245 mmol/l low sodium:glucose ratio 1:1)) compared with the previously recommended high-osmolarity WHO ORS solution (glucose 111, sodium 90, potassium 20, chloride 80 and bicarbonate 30, all in 311 mmol/l (standard WHO ORS with high 311 mmol/l with sodium:glucose ratio 1:3)). Moreover, the results suggest that low-osmolarity ORS solution leads to a greater reduction in stool output and vomiting. No difference was seen in the incidence of hyponatraemia. The other systematic review reported no statistically significant difference between oral rehydration solutions with different sodium contents in terms of treatment failure (need for IVT) in well-nourished children with gastroenteritis and dehydration ⁶¹⁾. It also failed to show any consistent trend in favour of either high- or low-sodium ORS solution for rehydration ⁶²⁾.

In conclusion, oral rehydration solution of reduced osmolarity (<270 mOsm/l) is preferable to solutions with a high osmolarity (>311 mOsm/l). Reduced osmolarity oral rehydration solution solution was associated with a lower incidence of failure to rehydrate and also a greater reduction in stool output.

Evidence from a well-conducted systematic review found no statistically significant differences in stool output or duration of diarrhoea when children with non-cholera diarrhoea were treated with rice-based oral rehydration solution solution compared with the traditional glucose-based oral rehydration solution solution. However, in children with cholera, rice-based oral rehydration solution solution was associated with a reduction in stool output and duration of diarrhoea ⁶³⁾.

Administration

Generally, 50 mL/kg is given over 4 h for mild dehydration and 100 mL/kg for moderate. For each diarrheal stool, an additional 10 mL/kg (up to 240 mL) is given. After 4 h, the patient is reassessed. If signs of dehydration persist, the same volume is repeated. Patients with diarrhea may require many liters of fluid/day.

• Or the approximate amount of oral rehydration solution (in milliliters) needed can also be calculated by multiplying the patient’s weight in kg by 75 ⁶⁴⁾.
• A rough estimate of oral rehydration rate for older children and adults is 100 ml oral rehydration solution every five minutes, until the patient stabilizes ⁶⁵⁾.
• During the initial stages of therapy, while still dehydrated, adults can consume as much as 1000 ml of oral rehydration solution per hour, if necessary, and children as much as 20 ml/kg body weight per hour.
• The volumes and time shown are guidelines based on usual needs. If necessary, amount and frequency can be increased, or the oral rehydration solution can be given at the same rate for a longer period to achieve adequate rehydration. Similarly, the amount of fluid can be decreased if hydration is achieved earlier than expected.
• If the patient requests more than the prescribed oral rehydration solution solution, give more.
• Patients should continue to eat a normal diet or resume a normal diet once vomiting stops.

Vomiting usually should not deter oral rehydration (unless there is bowel obstruction or other contraindication) because vomiting typically abates over time. Small, frequent amounts are used, starting with 5 mL every 5 min and increasing gradually as tolerated. The calculated volume required over a 4-h period can be divided into 4 separate portions. These 4 aliquots can then be divided into 12 smaller aliquots and given every 5 min over the course of an hour with a syringe if needed.

In children with diarrhea, oral intake often precipitates a diarrheal stool, so the same volume should be given in fewer aliquots.

Once the deficit has been replaced, an oral maintenance solution containing less Na should be used. Children should eat an age-appropriate diet as soon as they have been rehydrated and are not vomiting. Infants may resume breastfeeding or formula.

Signs of Adequate Rehydration

• Skin goes back normally when pinched
• Thirst has subsided
• Urine has been passed
• Pulse is strong

Infants and children

For infants and children who have become dehydrated from diarrhea, vomiting or fever, use an oral rehydration solution such as Pedialyte or Hydralyte. These solutions contain water and salts in specific proportions to replenish both fluids and electrolytes.

Babies

Start with about a teaspoon (5 milliliters) every one to five minutes and increase as tolerated. It may be easier to use a syringe for very young children.

Giving your baby regular sips (a few times an hour) of oral rehydration solution in addition to their usual feed (breastmilk, formula milk and water) will help to replace lost fluids, salts and sugars.

Avoid giving your baby fruit juice, particularly if they have diarrhoea and vomiting, because it can make it worse.

In a case–control study from Bangladesh ⁶⁶⁾, children aged between 1 and 35 months were selected for study inclusion if they had watery diarrhoea for 6 days or less at first presentation and had been breastfeeding up to the time of onset of diarrhoea. All were assessed for dehydration and were classified as ‘cases’ (with moderate to severe dehydration if there was a definite decrease in skin elasticity and presence of one or more of following signs: sunken eyes, failure to urinate for 6 hours, sunken anterior fontanelle, rapid and weak pulse) or as ‘controls’ (with no dehydration or mild dehydration if they did not fulfil those clinical criteria). Home oral rehydration solution therapy use was defined as giving either pre-packaged oral rehydration solution or home-made salt and sugar solution. There were 285 cases and 728 controls. After controlling for confounding factors (lack of maternal education, history of vomiting, high stool frequency, young age and infection with Vibrio cholerae), the risk of dehydration was five times higher in infants whose mothers stopped breastfeeding compared with infants whose mothers continued to breastfeed following the onset of diarrhoea ⁶⁷⁾. Similarly, the risk of dehydration was 1.5 times higher in infants who did not receive any oral rehydration solution therapy at home compared with those who received plentiful oral rehydration solution therapy (total volume ≥ 250 ml). Infants receiving smaller amounts of oral rehydration solution therapy (≤ 250 ml) before admission had an 18% higher risk of dehydration compared with those receiving plentiful oral rehydration solution therapy, but the risk was not statistically significant. Evidence from a case–control study indicated that cessation of breastfeeding in children with gastroenteritis was associated with an increased risk of dehydration. This study also suggested that oral fluid supplementation begun at home and given in good quantity was associated with a reduced risk of dehydration ⁶⁸⁾.

In children with gastroenteritis but without clinical dehydration:

• continue breastfeeding and other milk feeds.
• encourage fluid intake.
• discourage the drinking of fruit juices and carbonated drinks, especially in those at increased risk of dehydration.
• offer oral rehydration salt (ORS) solution as supplemental fluid to those at increased risk of dehydration.

Children

Children who are dehydrated should also take an oral rehydration solution such as Pedialyte or Hydralyte. These solutions contain water and salts in specific proportions to replenish both fluids and electrolytes.

If your child is finding it difficult to hold down fluids because of vomiting, give them smaller amounts more frequently. You may find it easier to use a spoon or a syringe.

Recommendation on oral rehydration therapy in children ⁶⁹⁾

In children with clinical dehydration, including hypernatraemic dehydration:

• use low-osmolarity ORS solution (240–250 mOsm/l)* for oral rehydration therapy
• give 50 ml/kg for fluid deficit replacement over 4 hours as well as maintenance fluid
• give the ORS solution frequently and in small amounts
• consider supplementation with their usual fluids (including milk feeds or water, but not fruit juices or carbonated drinks) if they refuse to take sufficient
• quantities of ORS solution and do not have red flag symptoms or signs (see Table 3)
• consider giving the ORS solution via a nasogastric tube if they are unable to drink it or if they vomit persistently
• monitor the response to oral rehydration therapy by regular clinical assessment.

However, some children may not tolerate oral rehydration therapy, either because they are unable to drink oral rehydration solution solution in adequate quantities or because they persistently vomit. In such cases, oral rehydration solution solution could be administered via a nasogastric tube, rather than changing to intravenous fluid therapy. This overcomes the problem of oral rehydration solution refusal. Continuous infusion of oral rehydration solution via a nasogastric tube might reduce the risk of vomiting.

Adults

• Most adults with mild to moderate dehydration from diarrhea, vomiting or fever can improve their condition by drinking more water or other liquids. Diarrhea may be worsened by full-strength fruit juice and soft drinks.

If you work or exercise outdoors during hot or humid weather, cool water is your best bet. Sports drinks containing electrolytes and a carbohydrate solution also may be helpful.

• Sports drink for exercise or working outdoors during hot and humid weather ⁷⁰⁾:

Sports drinks make an excellent fuel and hydration choice because they are a mix of carbohydrates and water. For exercise lasting anywhere from 60 minutes to
several hours, drinking carbohydrate beverages significantly boosts endurance performance compared to drinking water. According to some research, you can
expect an improvement in endurance of about 20 percent or more in workouts lasting over 90 minutes.

• Most commercial sports drinks supply a blend of sugars: four to nine percent solution, or 13 to 19 grams of carbs, per eight ounces.
• Drinking one-and-a-half to four cups per hour (more if you have heavy sweat losses) will provide you with both the fluid and carbs you need for endurance.
• Choose a beverage flavor you enjoy to encourage you to drink appropriate amounts.
• Fitness waters do not provide enough carbohydrate to boost endurance, but they can keep you hydrated.
• Drinking before and after exercise is also an important factor in maintaining proper hydration levels.

When you have diarrhea or gastroenteritis

Diarrhea is the passage of loose or watery stool ⁷¹⁾. For some, diarrhea is mild and will go away within a few days ⁷²⁾. For others, it may last longer. It can make you lose too much fluid (dehydrated) and feel weak. It can also lead to unhealthy weight loss.

The stomach flu (viral gastroenteritis) is a common cause of diarrhea ⁷³⁾. Medical treatments, such as antibiotics and some cancer treatments can also cause diarrhea.

How to Relieve Diarrhea

These things may help you feel better if you have diarrhea:

• Drink 8 to 10 glasses of clear fluids every day. Water is best.
• Drink at least 1 cup (240 milliliters) of liquid every time you have a loose bowel movement.
• Eat small meals throughout the day, instead of 3 big meals.
• Eat some salty foods, such as pretzels, soup, and sports drinks.
• Eat some high potassium foods, such as bananas, potatoes without the skin, and fruit juices.

Your provider may also recommend a special medicine for diarrhea. Take this medicine as you have been told to take it.

Eating When you Have Diarrhea

You can bake or broil beef, pork, chicken, fish, or turkey. Cooked eggs are also OK. Use low-fat milk, cheese, or yogurt.

If you have very severe diarrhea, you may need to stop eating or drinking dairy products for a few days.

Eat bread products made from refined, white flour. Pasta, white rice, and cereals such as cream of wheat, farina, oatmeal, and cornflakes are OK. You may also try pancakes and waffles made with white flour, and cornbread. But don’t add too much honey or syrup.

You should eat vegetables, including carrots, green beans, mushrooms, beets, asparagus tips, acorn squash, and peeled zucchini. Cook them first. Baked potatoes are OK. In general, removing seeds and skins is best.

Some desserts and snacks to try include fruit-flavored gelatin, fruit-flavored ice pops, cakes, cookies, or sherbet.

Things you Should Avoid Eating or Drinking

You should avoid certain kinds of foods when you have diarrhea, including fried foods and greasy foods.

Avoid fruits and vegetables that can cause gas, such as broccoli, peppers, beans, peas, berries, prunes, chickpeas, green leafy vegetables, and corn.

Avoid caffeine, alcohol, and carbonated drinks.

Limit or cut out milk and other dairy products if they are making your diarrhea worse or causing gas and bloating.

When to See a Doctor

See your health care provider if you have:

• The diarrhea gets worse or does not get better in 2 days for an infant or child, or 5 days for adults
• Stools with an unusual odor or color
• Nausea or vomiting
• Blood or mucus in your stool
• A fever that does not go away
• Stomach pain

Complications of Dehydration

Dehydration can lead to serious complications, including:

Permanent brain damage.

Death.

Heat Injury or Heatstroke

If you don’t drink enough fluids when you’re exercising vigorously and perspiring heavily, you may end up with a heat injury, ranging in severity from mild heat cramps to heat exhaustion or potentially life-threatening heatstroke ⁷⁴⁾.

Heat injuries (heatstroke) can occur due to high temperatures and humidity ⁷⁵⁾. Heat exhaustion or heatstroke can develop quickly over a few minutes, or gradually over several hours or days. You are more likely to feel the effects of heat sooner if:

• You are not used to high temperatures or high humidity.
• You are a child or an older adult.
• You are already ill from another cause (such as diabetes or a heart or lung condition) and dehydrated (e.g. gastro diarhhea) or have been injured.
• You are obese.
• You are doing strenuous exercise for long periods, such as military soldiers, athletes, hikers and manual workers. Even a person who is in good shape can suffer heat illness if warning signs are ignored.

You’re more likely to experience problems if you’re dehydrated, there’s little breeze or ventilation, or you’re wearing tight, restrictive clothing.

Certain medications can also increase your risk of developing heat exhaustion or heatstroke, including diuretics, antihistamines, beta-blockers, antipsychotics and recreational drugs, such as amphetamines and ecstasy.

The following make it harder for the body to regulate its temperature, and make a heat emergency more likely:

• Drinking alcohol before or during exposure to heat or high humidity
• Not drinking enough fluids when you’re active on warmer or hot days
• Heart disease
• Certain medicines: Examples are beta-blockers, water pills or diuretics, some medicines used to treat depression, psychosis, or ADHD
• Sweat gland problems
• Wearing too much clothing

Symptoms of Heatstroke

Heat cramps are the first stage of heat illness. If these symptoms are not treated, it can lead to heat exhaustion and then heat stroke.

Heat stroke occurs when the body is no longer able to regulate its temperature, and it keeps rising. Heat stroke can cause shock, brain damage, organ failure, and even death.

The early symptoms of heat cramps include:

• Muscle cramps and pains that most often occur in the legs or abdomen
• Very heavy sweating
• Fatigue
• Thirst

Later symptoms of heat exhaustion include:

• Headache
• Dizziness, lightheadedness
• Weakness
• Nausea and vomiting
• Cool, moist skin
• Dark urine

The symptoms of heatstroke include (call your local emergency number right away):

• Fever — temperature above 104°F (40°C)
• Irrational behavior
• Extreme confusion
• Dry, hot, and red skin
• Rapid, shallow breathing
• Rapid, weak pulse
• Seizures
• Unconsciousness

First Aid for Heatstroke

If you think a person may have heatstroke or heat emergency:

• Have the person lie down in a cool place. Raise the person’s feet about 12 inches (30 centimeters).
• Remove any unnecessary clothing to expose as much of their skin as possible.
• Apply cool, wet cloths (or cool water directly) to the person’s skin and use a fan to lower body temperature. Place cold compresses on the person’s neck, groin, and armpits.
• Fan their skin while it’s moist – this will help the water to evaporate, which will help their skin cool down.
• If alert, give the person a beverage to sip (such as a sports drink or water), or make a salted drink by adding a teaspoon (6 grams) of salt per quart (1 liter) of water.
• Give a half cup (120 milliliters) every 15 minutes. Cool water will do if salt beverages are not available.
• For muscle cramps, give beverages as noted above and massage affected muscles gently, but firmly, until they relax.
• If the person shows signs of shock (bluish lips and fingernails and decreased alertness), starts having seizures, or loses consciousness, call 911 and give first aid as needed.

Stay with the person until they’re feeling better. Most people should start to recover within 30 minutes.

If the person is unconscious, you should follow the steps above and place the person in the recovery position until help arrives (see below). If they have a seizure, move nearby objects out of the way to prevent injury.

Follow these precautions:

• DO NOT give the person medications that are used to treat fever (such as aspirin or acetaminophen). They will not help, and they may be harmful.
• DO NOT give the person salt tablets.
• DO NOT give the person liquids that contain alcohol or caffeine. They will make it harder for the body to control its internal temperature.
• DO NOT use alcohol rubs on the person’s skin.
• DO NOT give the person anything by mouth (not even salted drinks) if the person is vomiting or unconscious.

Prevention of Heatstroke

Heat exhaustion and heatstroke can often be prevented by taking sensible precautions when it’s very hot.

During the summer, check for heatwave warnings, so you’re aware when there’s a potential danger. The government uses a system called Heat-Health Watch to warn people about the chances of a heatwave. This is a system of four different warning levels based on the expected temperature.

The first step in preventing heat illnesses is thinking ahead.

• Find out what the temperature will be for the whole day when you will be outdoors.
• Think about how you have dealt with heat in the past.
• Make sure you will have plenty of fluids to drink.
• Find out if there is shade available where you are going.
• Learn the early signs of heat illness.

To help prevent heat illnesses:

• Wear loose-fitting, lightweight and light-colored clothing in hot weather.
• Rest often and seek shade when possible.
• Avoid exercise or heavy physical activity outdoors during hot or humid weather.
• Drink plenty of fluids every day. Drink more fluids before, during, and after physical activity.
• Be very careful to avoid overheating if you are taking drugs that impair heat regulation, or if you are overweight or elderly.
• Be careful of hot cars in the summer. Allow the car to cool off before getting in.
• NEVER leave a child sitting in a car exposed to the hot sun, even after opening windows.

Stay out of the heat

• Keep out of the sun between 11am and 3pm.
• If you have to go out in the heat, walk in the shade, apply sunscreen and wear a hat and light scarf.
• Avoid extreme physical exertion.
• Wear light, loose-fitting cotton clothes.

If you’re travelling to a hot country, be particularly careful for at least the first few days, until you get used to the temperature.

Cool yourself down

• Have plenty of cold drinks, and avoid excess alcohol, caffeine and hot drinks.
• Eat cold foods, particularly salads and fruit with a high water content.
• Take a cool shower or bath.
• Sprinkle water over your skin or clothing, or keep a damp cloth on the back of your neck.

If you’re not urinating frequently or your urine is dark, it’s a sign that you’re becoming dehydrated and need to drink more.

Keep your environment cool

• Keep windows and curtains that are exposed to the sun closed during the day, but open windows at night when the temperature has dropped.
• If possible, move into a cooler room, especially for sleeping.
• Electric fans may provide some relief.
• Turn off non-essential lights and electrical equipment, as they generate heat.
• Keep indoor plants and bowls of water in the house, as these can cool the air.

In the longer term, it can help to have your loft and cavity walls insulated, as this will keep the heat in when it’s cold and keep it out when it’s hot. Using light-colored, reflective external paint on your house may also be useful.

Look out for others

• Keep an eye on isolated, elderly, ill or very young people and make sure they are able to keep cool.
• Ensure that babies, children or elderly people are not left alone in stationary cars.
• Check on elderly or sick neighbours, family or friends every day during a heatwave.
• Be alert and call a doctor or social services if someone is unwell or further help is needed.

Urinary and kidney problems

• Prolonged or repeated bouts of dehydration can cause urinary tract infections, kidney stones and even kidney failure.

Seizures

• Electrolytes — such as potassium and sodium — help carry electrical signals from cell to cell. If your electrolytes are out of balance, the normal electrical messages can become mixed up, which can lead to involuntary muscle contractions and sometimes to a loss of consciousness.

Low blood volume shock (hypovolemic shock)

• This is one of the most serious, and sometimes life-threatening, complications of dehydration. It occurs when low blood volume causes a drop in blood pressure and a drop in the amount of oxygen in your body.

How to Prevent Dehydration

Since dehydration can be a life-threatening, drink small amounts of water over a period of time can prevent dehydration. Taking too much all at once can overload your stomach and make you throw up. For people exercising in the heat and losing a lot of minerals in sweat, sports drinks can be helpful. Avoid any drinks that have caffeine.

What is Viral gastroenteritis (stomach flu)

Viral gastroenteritis is present when a virus causes an infection of the stomach and intestine. The infection can lead to diarrhea and vomiting. It is sometimes called the “stomach flu.”

Causes of Viral gastroenteritis

Gastroenteritis can affect one person or a group of people who all ate the same food or drank the same water. The germs may get into your system in many ways:

• Directly from food or water
• By way of objects such as plates and eating utensils
• Passed from person to person by way of close contact.

Many types of viruses can cause gastroenteritis. The most common viruses are:

• Norovirus (Norwalk-like virus) is common among school-age children. It may also cause outbreaks in hospitals and on cruise ships.
• Rotavirus is the leading cause in children. It can also infect adults who are exposed to children with the virus, and people living in nursing homes.
• Astrovirus.
• Enteric adenovirus.

People with the highest risk for a severe infection include young children, older adults, and people who have a suppressed immune system.

Symptoms of Viral gastroenteritis

Symptoms most often appear within 4 to 48 hours after contact with the virus. Common symptoms include:

• Abdominal pain
• Diarrhea
• Nausea and vomiting

Other symptoms may include:

• Chills, clammy skin, or sweating
• Fever
• Joint stiffness or muscle pain
• Poor feeding
• Weight loss

Exams and Tests for Viral gastroenteritis

The health care provider will look for signs of dehydration, including:

• Dry or sticky mouth
• Lethargy or coma (severe dehydration)
• Low blood pressure
• Low or no urine output, concentrated urine that looks dark yellow
• Sunken soft spots (fontanelles) on the top of an infant’s head
• No tears
• Sunken eyes

Tests of stool samples may be used to identify the virus that is causing the sickness. Most of the time, this test is not needed. A stool culture may be done to find out if the problem is being caused by bacteria.

Treatment of Viral gastroenteritis

The goal of treatment is to make sure the body has enough water and fluids. Fluids and electrolytes (salt and minerals) that are lost through diarrhea or vomiting must be replaced by drinking extra fluids. Even if you are able to eat, you should still drink extra fluids between meals.

• Older children and adults can drink sports beverages such as Gatorade, but these should not be used for younger children. Instead, use the electrolyte and fluid replacement solutions or freezer pops available in food and drug stores.
• Do NOT use fruit juice (including apple juice), sodas or cola (flat or bubbly), Jell-O, or broth. These liquids do not replace lost minerals and can make diarrhea worse.
• Drink small amounts of fluid (2 to 4 oz. or 60 to 120 mL) every 30 to 60 minutes. Do not try to force down large amounts of fluid at one time, which can cause vomiting. Use a teaspoon (5 milliliters) or syringe for an infant or small child.
• Babies can continue to drink breast milk or formula along with extra fluids. You do NOT need to switch to a soy formula.

Try eating small amounts of food frequently. Foods to try include:

• Cereals, bread, potatoes, lean meats
• Plain yogurt, bananas, fresh apples
• Vegetables

If you have diarrhea and are unable to drink or keep down fluids because of nausea or vomiting, you may need fluids through a vein (IV). Infants and young children are more likely to need IV fluids.

Parents should closely monitor the number of wet diapers an infant or young child has. Fewer wet diapers is a sign that the infant needs more fluids.

People taking water pills (diuretics) who develop diarrhea may be told by their provider to stop taking them until symptoms improve. However, DO NOT stop taking any prescription medicine without first talking to your provider.

Antibiotics do not work for viruses.

You can buy medicines at the drugstore that can help stop or slow diarrhea.

• Do not use these medicines without talking to your provider if you have bloody diarrhea, a fever, or if the diarrhea is severe.
• Do not give these medicines to children.

Outlook (Prognosis) for Viral gastroenteritis

For most people, the illness goes away in a few days without treatment.

Possible Complications of Viral gastroenteritis

Severe dehydration can occur in infants and young children.

When to See a Medical Professional

See your provider if diarrhea lasts for more than several days or if dehydration occurs. You should also contact your provider if you or your child has these symptoms:

• Blood in the stool
• Confusion
• Dizziness
• Dry mouth
• Feeling faint
• Nausea
• No tears when crying
• No urine for 8 hours or more
• Sunken appearance to the eyes
• Sunken soft spot on an infant’s head (fontanelle).

Prevention of Viral gastroenteritis

Most viruses and bacteria are passed from person to person by unwashed hands. The best way to prevent stomach flu is to handle food properly and wash your hands thoroughly after using the toilet.

A vaccine to prevent rotavirus infection is recommended for infants starting at age 2 months.