Acute hyponatremia in emergency care settings can be life-threatening due to neurological complications such as cerebral edema. While water intoxication is a well-recognized cause of acute severe hyponatremia with prominent neurologic manifestations, non-neurologic complications such as intravascular hemolysis are rarely reported. We report a rare case of acute hyponatremia, initially manifesting as intravascular hemolysis, due to water intoxication over just two hours.

A 67-year-old woman presented to the emergency department in an agitated state (Glasgow Coma Scale score of 13). She had a history of untreated depressive symptoms. She had intentionally confined herself to a bathroom for approximately two hours, repeatedly drinking tap water using a 500 mL bottle. Two hours after being found in the bathroom, she was taken to the emergency room. On arrival, serum sodium was 111 mEq/L and plasma osmolality was 233 mOsm/kg. Initial urine appeared reddish-brown, raising suspicion of hemoglobinuria. Laboratory findings revealed markedly elevated levels of creatine kinase, lactate dehydrogenase, and myoglobinuria, and undetectable serum haptoglobin. She was diagnosed with water intoxication causing intravascular hemolysis and rhabdomyolysis. She was managed with fluid restriction in the intensive care unit. As serum sodium normalized, her mental status fully recovered, and there was no recurrence of hemolysis and rhabdomyolysis.

Water intoxication over a short period may lead to intravascular hemolysis due to an abrupt decline in plasma osmolality. Clinicians should be aware that acute severe hyponatremia, including that due to water intoxication, may initially present as non-neurologic manifestations, and early detection of hemolysis is essential to prevent secondary life-threatening sequelae.