Water intoxication
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. 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 (3 gallons) 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.
High risk factors
Gastroenteritis, particularly in infants and children
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 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.
Low body mass (infants)
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]
Endurance sports
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.
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 hyponatremic symptoms.
Medical conditions
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.
Treatment
Mild intoxication may remain asymptomatic and require only fluid restriction.
In more severe cases, treatment consists of:
Diuretics to increase urination, which are most effective for excess blood
volume
Saline given intravenously to restore sodium electrolyte levels
Vasopressin receptor antagonists
Prevention
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.
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