Treatment of severe hyponatremia: Conventional and novel aspects

Hyponatremia is a frequent electrolyte disorder. A hyponatremia is called a cute severe (<115 mM) when the duration has been <36 to 48 h. Such patients often have advanced symptoms as a result of brain edema. Acute severe hypo natremia is a medical emergency. It should be corrected rapidly to approxim ately 130 mM to prevent permanent brain damage. In contrast, in chronic sev ere hyponatremia (>4 to 6 d), there is no brain edema and symptoms are usua lly mild. In such patients, a number of authors have recommended a correcti on rate <0.5 mM/h to approximately 130 mM to minimize the risk of cerebral myelinolysis. Sometimes it is not possible to diagnose whether a severe hyp onatremia is acute or chronic. In such cases, an initial imaging procedure is helpful in deciding whether rapid or slow correction should be prescribe d. The modalities of treatment of severe hyponatremia have so far consisted of infusions of hypertonic saline plus fluid restriction. In the near futu re, vasopressin antagonists will become available. Preliminary experience h as already demonstrated their efficiency of inducing a sustained water diur esis and a correction of hyponatremia.