A. Jha 1 , K. Bernard 1 , D. Wilson 1 , R. Quinlin 1 ; 1 University of Pittsburgh Medical Center Shadyside, Pittsburgh, PA LEARNING OBJECTIVES: 1) To recognize rhabdomyolysis due to morphine. 2) To consider rhabdomyolysis in the differential diagnosis of post-operative renal failure. CASE INFORMATION: A 33-yr. old female underwent a laparoscopic`Roux-en-Y' gastroplasty under general anesthesia for morbid obesity. The anesthesia was induced by Midazolam, Fentanyl, Rocuronium and Succinylcholine. There was no masseter rigidity, or hyperthermia noted. Maintenance of anesthesia was done by Nitrous oxide, Propofol and Fentanyl. The patient had an uneventful perioperative course. There was no hematoma, or muscle tenderness following surgery. Morphine PCA was started. She has a past medical history of sleep apnea, hypertension, tubal ligation and hysterectomy without any complications. Her medications include Sertraline, Hydrochlorothiazide, Enalapril, and Albuterol inhaler. Her family history was unremarkable. The next morning she was found unresponsive and hypoventilating. An ABG revealed acute respiratory acidosis. She received Naloxone and the ABG normalized. Lab data revealed BUN -4 mg/dl, creatinine-2.0mg/dl (baseline -0.8), calcium -6.7 mg/dl, phosphorus-5.7mg/dl, magnesium-1.6mg/dl, sodium-138meq/L, potassium-4.1 meq/L, chloride-103 meq/L, C02-21meq/L, CPK-658 IU/L, CPK-MB-5.8 IU/L, Urine myoglobin-374( < 27mcg/L). EKG showed sinus tachycardia and an echocardiogram was normal. EEG, thyroid function, and serum Cortisol were normal. CPK levels increased to around 9400 IU/L and CPK-MB increased to 26 IU/L within two days. A diagnosis of morphine-induced rhabdomyolysis was made and patient was treated with D5Wand NaHCO3. Her Creatinine normalized the following day, and CPK, CPK-MB became normal on the 7th day. DISCUSSION: Prolonged surgery, electrolyte disturbances, infection and drugs are common causes of rhabdomyolysis and myoglobin-induced renal failure in the post-operative period. Morphine infrequently causes rhabdomyolysis. Proposed mechanism for morphine-induced rhabdomyolysis is myohypoxic necrosis and myocompression due to sedation related immobility. Reversal of narcotic effect with naloxone, withdrawing morphine, and hydration are the key components of management.