Water intoxication (also known as hyperhydration or water poisoning) is a potentially fatal disturbance in brain functions that results when the normal balance of electrolytes in the body is pushed outside of safe limits by over-consumption of water.[1] Normal, healthy (both physically and nutritionally) individuals have little to worry about accidentally consuming too much water. Nearly all deaths related to water intoxication in normal individuals have resulted either from water drinking contests, in which individuals attempt to consume more than 10 liters (10.5 quarts) of water over the course of just a few minutes, or long bouts of intensive exercise during which electrolytes are not properly replenished, yet massive amounts of fluid are still consumed.
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The severe diarrhea and vomiting associated with gastroenteritis can result in very large electrolyte losses. Gastroenteritis due to infectious agents (primarily rotavirus), is a major cause of infant and child death. Management of gastroenteritis requires replacing water and electrolytes in proportions that avoid both dehydration and water intoxication. Drinking water will replace lost water and avoid a dehydration, but if the person is unable to take any other drink or food then lost electrolytes will not be 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.
It can be very easy for children under 1 year old to absorb too much water, especially if the child is under nine months old. Because of their small body mass, it is easy to take in a large amount of water relative to body mass.[2]
Marathon runners are susceptible to water intoxication if they drink too much while running. This is caused when sodium levels drop below 135mmol/L when athletes consume large amounts of fluid. This has been noted to be the result of the encouragement of excessive fluid replacement by various guidelines. This has largely been identified in marathon runners as a dilutional hyponatremia. Medical personnel at marathon events are trained to immediately suspect water intoxication when runners collapse or show signs of confusion.
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.
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 hyponatremic symptoms.
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.
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.
Mild intoxication may remain asymptomatic and require only fluid restriction. In more severe cases, treatment consists of:
Water intoxication can be prevented if a person's intake of water and electrolytes closely matches his or her losses. The body's regulatory mechanisms provide a very generous margin of safety if the two are imbalanced, but some extreme activities (such as heavy, prolonged physical exertion), as well as disease states, can overwhelm or impair these mechanisms. Avoid situations that provoke extreme or prolonged perspiration. Drinking fluids that are specially balanced to replace lost electrolytes can also help to prevent intoxication. Eating regularly can provide needed electrolytes if only normal water is available for rehydration.
Sports drinks are popular among athletes because they provide the necessary electrolytes to support extended exercise. They help keep the body balanced and carrying the right amount of fluids. However, not all drinks advertised as sports drinks are suitable for this purpose, and professional advice should be sought for potentially risky situations such as those described above.
Note that a person's innate sense of thirst is more sensitive to overall dehydration than to changes in electrolytes. Thus, it is possible to develop water intoxication while trying to satisfy thirst, if one drinks a great deal of water over a short period. A dangerous drop in electrolytes, such as the hyponatremia that leads to water intoxication, will not have any effect on thirst if one is sufficiently dehydrated.
For people suffering from dehydration due to the heavy perspiration associated with heavy exertion or heat stress, drinking water to rehydrate is much more important than avoiding water intoxication, since the former is extremely common and the latter is rare. One should never avoid drinking water under such conditions; instead, other steps should be taken to ensure that electrolytes are replaced as well, as noted above.