Prophylactic Value of Beta Blockers

Abstract

The roles and safety of beta blockade following cardiac surgery have been controversial for three decades. In the 1960's and early 1970's it was feared that perioperative use of beta blockers would cause significant myocardial depression by either their direct antiadrenergic effects or the potentiation of the myocardial depressant effects of general anesthetics. Many recommended that beta blockers be discontinued from 48 hours [1,2] to as early as 2 weeks before surgery [3]. This practice was challenged after reports of worsening angina, myocardial infarction, ventricular tachycardia, and sudden death following the abrupt cessation of beta blockers in patients treated chronically with propranolol [4,5] as well as an increased incidence of perioperative complications in patients in whom beta blockers were discontinued preoperatively [6]. By the late 1970's the safety for continued beta blockade before and after cardiac surgery was demonstrated [7,8], and this strategy was tested for the prevention of postoperative complications, most often supraventricular arrhythmias. Herein we review the clinical trials testing various beta-adrenergic antagonists after cardiac surgery for the prevention of postoperative atrial fibrillation (Table 1) and offer recommendations for treatment. discontinuation 10 hours before surgery, or continuation of beta blockade until the day of surgery followed by low dose intravenous propranolol for 36 to 48 hours postoperatively. These three groups were compared also to 17 patients who did not receive propranolol either prior to or after surgery. The highest incidence of supraventricular arrhythmias was observed in the groups randomized to discontinuation of propranolol 48 or 10 hours before surgery when compared to the group receiving pre- and postoperative propranolol. The authors also noted a marked increase in the rate-pressure product during intubation and postoperative periods in the patients for whom the beta blocker was discontinued before surgery. The authors speculated that both findings were due to propranolol withdrawal following a hyperadrenergic response to stress.