Acute Water-intoxication from Compulsive Water-drinking

Abstract

Water -intoxication is not uncommon, though it can be overlooked or mistaken for Na depletion (Wynn and Rob, 1954). Most acute cases occur in surgical patients in the period immediately after operation when for one reason or another an excessive amount of fluid is given to a patient other than orally. Wynn and Rob (1954) have shown that for practical purposes if the blood sugar is normal the plas-ma-Na concentration defines the effective osmotic pressure. It is to the lowered plasma osmolarity and decrease in the osmolarity of the extracellular fluid, particularly where this is rapid (Cooke, 1960), that symptoms are due. The retained water is distributed through the whole of the body fluid and symptoms are those of cellular hydration, especially of the brain cells. The extracellular fluid is expanded but not sufficiently to produce pitting edema. The serum Na is lowered and symptoms may be expected with Na levels in the region of 120 mEq/1. Lower levels appear to be better tolerated when there is a slower onset. Cooke (1960) maintains that the appearance of symptoms of acute water-intoxication is more closely associated with the rate of change of serum-Na concentration than the absolute serum levels. Very low serum-Na concentrations are found only in cases of Na depletion. Another factor which it was suggested (Le Quesne and Lewis, 1953) may play a part in acute water-retention is excess production of antidiuretic hormone. This may follow surgical operations, trauma, hypotension, reduction in blood-volume, pain, fear, or virtually any stress. It is possible that withdrawal of alcohol in the first case reported might have acted as such a stress. Lastly, patients with latent or overt epilepsy are known to be more susceptible (Barlow and De Wardener, 1959), as are nervous or excitable dogs in animal experiments (Rowntree, 1926). This may also have been a factor in the first case reported. Prevention is more important than treatment. Limitation of fluid intake is obvious. When severe intoxication occurs intravenous hypertonic saline can be given. But caution must be exercised and K may be needed where the levels of K before treatment are normal or lower. Some cases with low serum-Na levels, however, are associated with hyperpotassaemia, which underlines the need for caution (Cooke, 1960).