The effects of morphine and halothane anaesthesia on urine norepinephrine during and after coronary artery surgery.

Urine concentrations and excretion rates of norepinephrine were measured in 28 patients anaesthetized with halothane or morphine before, during and for two hours after aortocoronary artery grafting procedures. All patients were paralyzed with d-tubocurarine, intubated and respiration was controlled. Urine was obtained for 90 minutes before induction, during induction, before, during and after bypass and postoperatively. In patients anaesthetized with halothane, urinary norepinephrine concentrations and excretion rates were not significantly different from preoperative values until the postoperative period. Patients anaesthetized with morphine did not have urine norepinephrine concentrations different from preoperative values until bypass, when they became significantly increased. All subsequent urine norepinephrine concentrations and excretion rates were significantly elevated when compared to preoperative values. These findings do not indicate a mechanism but they do demonstrate that morphine anaesthesia is associated with increased urinary and probably also increased plasma levels of norepinephrine during and after cardiopulmonary bypass in patients undergoing coronary artery operations.