Beneficial effect of continuation of propranolol through coronary bypass surgery

The safety and beneficial effect of continuation of propranolol (Pr) through coronary bypass surgery (CBS) was studied in two groups of patients. In the control group (50 patients) Pr was discontinued 24 h before CBS without reinstitution afterwards. In the propranolol group the drug was maintained up to 4 to 10 h before surgery and was restarted within 24 h afterwards. The incidence of subendocardial myocardial infarction was significantly lower in the Pr group (1 out of 30 vs 10 out of 50, p less than 0.05) while the incidence of transmural infarction was the same in both groups (3 out of 30, 10%, vs 5 out of 50, 10%). The incidence of supraventricular tachycardias during the first three postoperative days was significantly lower in the propranolol group compared to control (5% vs 30%, p less than 0.01). The 24 h urinary epinephrine and norepinephrine excretion was significantly greater than normal the day before surgery (136 +/- 12 vs 39 +/- 4 micrograms/24 h, p less than 0.01), and was still high two weeks after surgery (115.1 +/- 14 micrograms/24 h). There were no complications related to propranolol. The left ventricular function as measured from the systolic time intervals was the same pre- and postoperatively in both groups. The results of this study show that administration of propranolol up to 4 h before coronary bypass and reinstitution immediately afterwards is safe and beneficial.