Clinical pharmacology of the new beta-adrenergic blocking drugs. Part 10. Beta-adrenoceptor blockade and coronary artery surgery

Abstract

In an attempt to resolve the controversy concerning propranolol therapy in patients undergoing coronary artery revascularization surgery, 54 consecutive patients with stable angina pectoris receiving chronic propranolol therapy entered a randomized trial and were compared with 17 patients on no propranolol therapy (group I). The 54 patients were divided into three treatment groups: in group II (n = 17) propranolol was abruptly withdrawn 48 hours prior to surgery, in group III (n = 18) propranolol was abruptly withdrawn 10 hours prior to surgery, in group IV (n = 19) propranolol was maintained until the day of surgery, half the usual dose was given 2 hours prior to surgery, and intravenous propranolol was administered every four hours postoperatively. Patients in group II and III had significantly higher increases in the rate-pressure product (RPP) during intubation, and in the postoperative periods compared to patients in groups I and IV. Group IV had the lowest increase in RPP during intubation and a significantly lower incidence of postoperative supraventricular arrhythmias. Patients abruptly withdrawn from propranolol, at 10 or 48 hours preoperatively, are more prone to increments in myocardial oxygen demands than those patients not treated with propranolol postoperatively or who were maintained on the drug. Plasma renin activity, although lower in patients treated with propranolol (group IV), did not seem to play a role in the RPP increments seen. The increased sympathetic tone associated with intubation and the postoperative period most likely contribute to the increments in RPP and the increased incidence of arrhythmia. These data show that (1) propranolol may be given safely to patients at the time of coronary artery bypass and may be maintained postoperatively without a decrement in left ventricular performance; (2) there is a “rebound effect” or increased sympathetic activity in patients who have propranolol abruptly withdrawn 10 or 48 hours prior to surgery. This “rebound effect” causes a marked increase in myocardial oxygen demands during intubation and the postoperative periods, with an increased incidence of arrhythmias. (3) Continuous propranolol treatment up until the time of surgery with maintenance of intravenous therapy in the immediate postoperative period provides protection against these complications. (4) The data and implications can reasonably be expected to apply to propranolol-treated patients with angina pectoris undergoing general anesthesia and noncardiac surgical procedures.