Water intoxication risk factors
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Risk Factors
Low Body Mass (Infants)
It can be very easy for children under a year old to absorb too much water – especially if the child is under nine months old, because with their small body mass, it is easy to take in a large amount of water relative to body mass. It is also possible for a child to absorb too much water if submerged in it.[1]
Endurance Sports
Marathon runners are susceptible to water intoxication if they drink only water while running. Although sweat is relatively hypotonic compared with body fluids, marathon runners perspire heavily for long periods, potentially causing their sodium levels to drop when they consume large amounts of fluids to quench their thirst. The replacement fluids may not contain sufficient sodium to replace what has been lost, and this puts them at high risk for water intoxication. Medical personnel at marathon events are trained to immediately suspect water intoxication when runners collapse or show signs of confusion. Properly designed electrolyte-replacement drinks and some sports drinks include electrolytes that make them roughly isotonic with sweat, which helps to prevent water intoxication.
Note that overconsumption of sodium (in drinks or also in food), as well as inadequate intake of water, can cause hypernatremia, a disorder that is nearly the opposite of water intoxication and equally dangerous. Improper use of salt tablets can cause hypernatremia also.
Overexertion and Heat Stress
Any activity or situation that promotes heavy sweating can lead to water intoxication when water is consumed to replace lost fluids. Persons working in extreme heat and/or humidity for long periods must take care to drink and eat in ways that help to maintain electrolyte balance. Persons using drugs such as MDMA ("Ecstasy") may overexert themselves, perspire heavily, and then drink large amounts of water to rehydrate, leading to electrolyte imbalance and water intoxication (See the case of Leah Betts). Even people who are resting quietly in extreme heat or humidity may run the risk of water intoxication if they drink large amounts of water over short periods for rehydration.
Psychiatric Conditions
Psychogenic polydipsia is the psychiatric condition in which patients feel compelled to drink large quantities of water, thus putting them at risk of water intoxication. This condition can be especially dangerous if the patient also exhibits other psychiatric indications (as is often the case), as his or her care-takers might misinterpret the hyponatraemic symptoms.
Specific Disease
Diarrhea and vomiting can result in very large electrolyte losses, and although drinking water will replace lost water, the lost electrolytes may not be adequately replaced, which can result in water intoxication. Replacement fluids for vomiting and diarrhea should be properly balanced to make them isotonic with the fluids lost in these conditions. Special formulations exist for oral rehydration therapy in these cases.
A great many disorders can affect electrolyte balance, especially disorders of the kidneys. Diuretic therapy, mineralocorticoid deficiency, osmotic diuresis (as in the hyperglycemia of uncontrolled diabetes), and the multiple disorders associated with AIDS are other common causes of electrolyte imbalance, although they do not always produce water intoxication.
Iatrogenic
When an unconscious person is being fed intravenously (for example, total parenteral nutrition or via a nasogastric tube) the fluids given must be carefully balanced in composition to match fluids and electrolytes lost. These fluids are typically hypertonic, and so water is often co-administered. If the electrolytes are not monitored (even in an ambulatory patient) either hypernatremia or hyponatremia may result.
Some neurologic/psychiatric medications (Trileptal, among others) have been found to cause hyponatremia in some patients. Patients with diabetes insipidus are particularly vulnerable due to rapid fluid processing.
References