Severe hyponatraemia: Current concepts on pathogenesis and treatment

Severe hyponatraemia (serum sodium < 120 mEq/L) is a serious electrolyte di sorder associated with life-threatening neurological complications. It deve lops most often when the ability of the kidney to excrete free water is Imp aired. The initial adaptation of the brain to hyponatraemia includes loss o f water, sodium, potassium and chloride Into the cerebrospinal fluid and th e late adaptation consists of the loss of organic osmolytes. Adaptation of the brain to hyponatraemia causes potential problems during therapy, as re- adaptation requires a considerably longer time. Rapid correction of hyponat raemia may lead to the development of the osmotic demyelination syndrome. T hough the ideal treatment for severe hyponatraemia remains controversial, a consensus regarding therapeutic guidelines has emerged. The rate of correc tion and the type of infusate depend on the duration and cause of the hypon atraemia, clinical presentation, volume status, renal function and the seru m potassium level. The prognosis of the osmotic demyelination syndrome is r ather dismal although several therapeutic modalities have been tried.