This report describes a 4-month-old infant with multisystem organ failure w
ho developed severe hypernatremia (sodium 168 mEq/l) due to rapid free wate
r removal associated with acute peritoneal dialysis instituted for fluid ov
erload. The current report describes the pathophysiology of the hypernatrem
ia, and its correction by low-sodium hypertonic peritoneal dialysis without
compromising ultrafiltration or supplementing with free water. Although pe
ritoneal dialysis can cause hypernatremia, a modified solute concentration
in the dialysate can treat the hypernatremia successfully.