Hyponatremia and rhabdomyolysis: a possible relationship.

A 40-year-old schizophrenic presenting with an acute toxic psychosis was found to be severely hyponatremic with a serum osmolality of 217 mOsm/kg. The patient was combative and required physical restraints. Shortly after admission the patient's serum transaminase level was elevated, and the next day the CPK value was 175,000 IU. In addition, his serum and urinary myoglobin levels were markedly raised. Shortly after rhabdomyolysis was diagnosed, the patient developed reversible acute renal failure presumably secondary to the myoglobinuria. This report examines the possibility that the severe hyponatremia and hypoosmolality caused his skeletal muscles to become potassium depleted, leading to rhabdomyolysis during the stenuous exercise involved in his battling the restraints.