[Cerebral symptoms in hyponatremia. Treatment and course]

Pronounced hyponatraemia results in serious neurological symptoms and the untreated condition is associated with a great mortality. An account is presented of nine hyponatraemic patients (plasma sodium 101-119 mmol/l) without cardiac, renal or hepatic disease who were admitted to a department for intensive care. In all of the patients, consciousness was compromised. Three patients had generalized convulsions and six patients had respiratory involvement which required respirator treatment in two patients. In one patient, the hyponatraemia had developed acutely. The remaining cases had developed chronically. One patient was confused for one month after admission and another patient developed classical central pontine myelinolysis after a latent period of seven days and which required admission for rehabilitation for several months. The remaining patients, including the acute patient, had recovered completely after a few days. The rate of correction for plasma sodium was calculated for the patients. Animal experimental and clinical accounts concerning the pathological physiology and treatment of hyponatraemia are reviewed. It is important to differentiate between acutely and chronically developed hyponatraemia as treatments differ considerably. Severe chronic hyponatraemia should be treated with a rate of correction of plasma sodium of 0.5 mmol/l/hour, and the normal range for plasma sodium should be aimed at after a couple of days. The risk involved in more rapid normalization is development of central pontine myelinolysis with severe neurological sequelae. Hypertonic sodium chloride must only be employed in cases of acutely developed hyponatraemia with convulsions. Acute hyponatraemia may otherwise be corrected with a rate of correction of plasma sodium of 1 mmol/l/hour or more.