POST TIME: 14 September, 2018 00:00 00 AM / LAST MODIFIED: 14 September, 2018 12:31:43 AM
Water Intoxication
By Dr Shamim Ahmed

Water Intoxication

To most of us, water intoxication, or water poisoning, is unfamiliar or unheard of. As physicians, we are often asked about the amount of fluid or glasses of water one should consume in a day. The answer is not easy and depends on a number of factors. However, as long as the colour of the urine is clear, the amount of water consumed should be considered as satisfactory.

One should be careful, particularly on hot, humid days that we often experience. Excessive water intake can lead to water intoxication, and ultimately death, because it acts on the body almost like a toxin. Under normal circumstances, an individual will not drink enough water to result in intoxication, but in a situation where judgment might be impaired by excessive sweating, heat stroke, drug use, or psychological distress, a large amount of water may be consumed too quickly. It could potentially lead to fatal disturbances in brain functions, resulting from imbalance of electrolytes in the body beyond safe limits due to over-hydration.

Water, just like any other substance, can be considered a poison when over-consumed in a specific period of time. Water intoxication mostly occurs when water is being consumed in a high quantity without giving the body the proper nutrients it needs to be healthy.

Under normal circumstances, accidentally consuming too much water is exceptionally rare. Nearly all deaths related to water intoxication occur when individuals attempt to drink large amounts of water following long bouts of intensive exercise, during which electrolytes are not properly replenished.

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 humidity for long periods must take care to drink and eat in ways that help to maintain electrolyte balance.

Water intoxication can lead to hyponatremia (low level of sodium), is a serious medical condition that results when someone drinks too much water too quickly. It can happen to athletes who drink too much after an event or to infants who are given too much water or heavily diluted milk formula. Hyponatremia occurs when the sodium levels in the body are heavily diluted, resulting in an overall loss of electrolyte balance.

Marathon runners are susceptible to water intoxication if they drink too much while running. This is caused when sodium levels drop below 135 mmol per litre when athletes consume large amounts of fluid. This may be due to excessive fluid replacement encouraged by various guidelines. This has largely been identified in marathon runners as dilutional hyponatremia.

At the onset of this condition, fluid outside the cells has an excessively low amount of solutes (such as sodium and other electrolytes) in comparison to that inside the cells, causing the fluid to shift (via osmosis) into the cells to balance its concentration. This causes the cells to swell. In the brain, this swelling increases intracranial pressure.

It is this increase in pressure which leads to the first observable symptoms of water intoxication: headache, changes in behaviour, confusion, irritability and drowsiness. These symptoms are sometimes followed by difficulty in breathing during exertion, muscle weakness and pain, twitching or cramping, nausea, vomiting, thirst and a dulled ability to perceive and interpret sensory information. As the condition persists, papillary and vital signs may result in bradycardia (slower heart rate) and widened pulse pressure. The cells in the brain may swell to the point where blood flow is interrupted resulting in cerebral edema.

Essentially, water intoxication drowns the cells of the body in fresh water. If a large amount of fluid is consumed over a short period of time, the cells will begin to swell because the kidneys cannot process the water quickly enough. The water starts to dilute the electrolyte levels in the body, and if enough water is consumed, the cells could actually burst. A low level of electrolytes can result in an irregular heartbeat, brain malfunction, and ultimately seizures and death.

Water intoxication can be prevented if a person's intake of water does not grossly exceed his or her fluid losses. Healthy kidneys are able to excrete approximately one litre of water per hour. However, stress (from prolonged physical exertion), as well as disease states, can greatly reduce this amount.

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.