Urinary excretion of morphine during and after valvular and coronary-artery surgery

The urines of 34 patients anesthetized with morphine for mitral-valve or aortic-valve replacement operations or for coronary-artery disease revascularization procedures were analyzed for morphine and morphine-3-glucuronide before, during and for two hours after operation. Patients who had coronary-artery disease had higher urinary flow rates and excreted greater proportions of the administered morphine during induction of anesthesia, throughout operation, and for two hours postoperatively than patients with valvular heart disease. Correlation of total urinary output with total free morphine excreted after two hours in the recovery room was high, r = .84. Urinary morphine in the glucuronide form increased progressively from the time of induction of anesthesia to the postoperative period and was greater than 91 per cent for all patients after two hours in the recovery room. Patients who had coronary-artery disease required mechanical postoperative ventilation for significantly shorter periods than did those with valvular heart disease. The duration of postoperative ventilation was negatively correlated with total urinary output and total free morphine excreted in the urine from induction of anesthesia until two hours postoperatively (r = .80 and r = .77, respectively). The data demonstrate that urinary excretion of free morphine and morphine-3-glucuronide during and early after operation is greater in patients who have coronary-artery disease than in those with valvular heart disease. The findings also suggest that duration of mechanical ventilation after morphine anesthesia and operation is inversely related to urinary output and excretion of free morphine. (Key words: Analgesics, narcotic, morphine; Biotransformation (drug), morphine.)