Physicians managing patients under hypothermia or after major operations, particularly cardiac procedures, will observe with increasing frequency an acute, seemingly paradoxical hyponatremia. The low serum sodium concentration develops abruptly, apparently out of proportion to the amount of fluid recently administered, and without producing any of the symptoms of water intoxication which might be expected to accompany such rapid dilution of electrolytes. As the underlying mechanism of this deceptive hyponatremia often is not appreciated, incorrect diagnosis and potentially harmful therapy may follow its discovery. A discussion of the problem therefore seems warranted.
Report of Cases
Typically, this type of hyponatremia has been discovered after 24 hours of therapeutic hypothermia or on the day following major surgery. On routine determination, a previously normal serum sodium concentration unexpectedly has been found below 120 mEq/liter in asymptomatic patients, as demonstrated in the following cases:
—A 13-year-old girl aspirated secretions 36 hours after