Sedation following cardiac surgery: evaluation of alfentanil and morphine in the presence of a computerized closed loop arterial pressure controller.

Forty patients who had undergone coronary artery graft surgery and who required vasodilator therapy for postoperative hypertension were given infusions of either alfentanil or morphine together with bolus doses of midazolam for sedation and analgesia while ventilation was controlled artificially. Sodium nitroprusside (SNP) was administered to both groups using a computer-controlled closed loop system which adjusted the infusion rate to maintain a preset target arterial pressure. Target pressure +/- 5, 10, 15 and 20 mm Hg was maintained longer in the group receiving alfentanil. This group also required less SNP per hour. No difference was noted between the groups in the time taken to regain spontaneous ventilation and to extubation of the trachea, although the alfentanil group tended to be sedated more deeply during the infusion. The main advantage of alfentanil over morphine at doses used in this study was its superior ability to attenuate hypertensive responses to noxious stimuli, providing improved haemodynamic stability.