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In the UK, we are presently in the middle of a considerable heat wave, with July 2006 declared the UK’s hottest month on record.¹ Both the Department of Health and NHS Direct have been quick to disseminate health advice,² particularly to parents and healthcare workers responsible for the care of children, about the dangers of exposure to heat and dehydration. This advice has emphasised the need for adequate fluid intake, particularly that of water. Notably, parents have been encouraged to “give babies plenty of cooled boiled water throughout the day”.³Although we believe this to be a sound advice to parents in most situations, it is important for clinicians to be aware of the risks of water intoxication, especially in infants. Water intoxication in children is well described previously⁴ and on the increase, if not reaching epidemic proportions, in the United States.⁵ It can cause considerable morbidity and mortality from hyponatraemia, brain swelling and seizures. Primarily associated with inappropriate dilution of formula feeds, bottled water has been described previously as a noteworthy cause.^6,7 Children are at particular risk as it is thought that apart from immature renal function, infants have a powerful thirst drive, which may impede their ability to curb intake. Bhalla et al⁸reported four cases of hyponatraemic seizures in the UK that were secondary to excessive solute ingestion.

Being a paediatric intensive care retrieval service, we have recently dealt with previously normal hyponatraemic children presenting with abnormal neurology and seizures. A 1?year?old child presented with status epilepticus after a 2?day history of vomiting, during which hypotonic fluids were given. The child required intravenous lorazepam and one dose of rectal paraldehyde to terminate the seizure, and was intubated, ventilated and transferred to a regional paediatric intensive care unit. The concetration of serum sodium on attendance was 116?mmol/l. The child was subsequently fluid restricted for 48?h.

Depending on age and sex, about 40 to 60% of body weight is water (younger people retain more water). Any substantial drop below the normal amount results in a potentially serious medical condition called dehydration. The body routinely loses about five pints of water a day through urination, fecal matter, sweating, and water vapor exhaled during respiration. The fluids people drink combined with water in food usually make up for that loss.
Ignoring thirst and excessive sweat could lead to heat exhaustion. Severe dehydration can result from extreme diarrhea or any other disorder that causes rapid water loss. In extreme cases dehydration can lead to shock and even death.
Parts affected: Every cell in the body contains water. Both the amount of water and the concentration of electrolytes( important chemicals; including sodium and potassium, used as cellular signals) are important to normal bodily functions. Sweating and diarrhea do not only remove water but also lower the amount of electrolytes in the blood. Among the more immediate effects of the loss of electrolytes in serious dehydration are problems with the circulatory system (rapid heartbeat) and nervous system (loss of consciousness, shock).
Related symptoms: Dehydration is often accompanied by excessive thirst, weight loss, and dry mucous membranes. With heat exhaustion the patient sweats profusely, turns pale, and has cool skin, rapid breathing, and a high pulse rate. The person may be dazed and confused, but usually remains conscious.
Associations: Dehydration is a symptom of various disorders that result in excessive fluid loss, including cholera, dysentery, and other forms of severe diarrhea. Some of these diseases stimulate vomiting as well as diarrhea, which makes it more difficult to replace lost fluids.
Prevention and possible actions: Drinking fluids at regular intervals while working or exercising in hot weather can help prevent heat exhaustion and other problems associated with mild dehydration. Administering fluids that contain electrolytes can prevent damage from severe dehydration caused by cholera or other forms of severe diarrhea.

For individuals at rest, indirect calorimetric determinations on the effects of body size, growth, disease, gender, drugs, nutrition, age, and environment on metabolism are very useful. The resting metabolic rate per unit body mass is greater in males than in females, greater in children than in the aged, greater in small-sized individuals than in large ones, and greater under extremes of heat and cold than under normal conditions.

But How is Indirect Calorimetry Utilized During Exercise? Read More