Adaptation to acute and chronic hyponatremia: implications for symptomatology, diagnosis, and therapy

Hyponatremia is often associated with a broad spectrum of neurological symptoms, occasionally leading to death in severe cases. Recent studies have clearly indicated that too rapid correction of severe hyponatremia can cause brain demyelination, which also produces neurological morbidity and mortality in some cases. This has caused a clinical conundrum regarding optimal treatment of hyponatremia, and may leave physicians uncertain about the most appropriate therapy for this important group of patients. Despite ongoing controversy about treatment guidelines and outcomes for specific subgroups of patients, a synthesis of recent clinical and experimental results suggests that the treatment of hyponatremic patients entails balancing the risks of hyponatremia against the risks of correction for each patient on an individualized basis. Although variability for both risks is great and one cannot accurately predict those patients who will develop neurological complications from either hyponatremia or its correction, a general consensus for rational treatment guidelines has nonetheless emerged. Following a discussion of the physiology and pathophysiology of brain adaptation to hyponatremia, this review will focus on the present consensus approach to therapy of hyponatremic patients.