THE TREATMENT OF SEVERE HYPONATREMIA

Severe hyponatremia may be chronic (days) or acute (hours), symptomati c or asymptomatic. Severe chronic symptomatic hyponatremia (serum sodi um concentration < 110 to 115 mM/liter) occurs most commonly in the sy ndrome of inappropriate antidiuretic hormone secretion (SIADH). The tr eatment of this hyponatremia is a challenge to practicing physicians, in part because an overly rapid correction of hyponatremia may cause b rain damage. The latter sometimes takes the form of central pontine my elinolysis (CPM). On the basis of available clinical and experimental literature, the rate of correction of this symptomatic hyponatremia sh ould be no more than 0.5 mM per liter per hour, and the initial treatm ent should be halted once a mildly hyponatremic range of the serum sod ium concentration has been reached (similar to 125 to 130 mM/liter). I n contrast, severe chronic asymptomatic hyponatremia map be treated su fficiently by a fluid restriction. On the other hand, severe symptomat ic acute hyponatremia should be treated promptly and rapidly, using hy pertonic saline, to initially reach a mildly hyponatremic level.