Effect of intraoperative propranolol on serum creatine kinase MB release in patients having elective cardiac...

Intraoperative beta blockade has been evaluated as an adjunct to hypothermic cold blood potassium cardioplegia by quantitating serum creatine kinase MB release. Randomization of 80 patients having coronary artery bypass grafting and 18 patients having valve replacement with or without bypass grafting resulted in 46 of the former and seven of the latter receiving propranolol 0.05 mg/kg 4 to 5 minutes before aortic cross-clamping. Among patients having bypass grafting, infarct size (in gram-equivalents) was 7.9 +/- 0.7 gm-Eq for the propranolol group and 10.3 +/- 0.8 (p less than 0.05) for the control group. Ischemic times were 71.6 +/- 2.8 and 78.3 +/- 3/4 minutes (p = NS), respectively. In valve replacement, infarct size was 9.9 +/- 1.9 gm-Eq for those receiving propranolol and 12.6 +/- 2.0 (p = NS) for the control subjects; ischemic times were 99.4 +/- 12.5 and 80.5 +/- 5.7 minutes, respectively. When the two groups receiving propranolol were combined, infarct size was 8.2 +/- 0.6 gm-Eq versus 10.9 +/- 0.7 (p less than 0.01). When ischemic time was plotted against infarct size, analysis by linear regression revealed a significant correlation for patients receiving propranolol and having bypass grafting (p less than 0.01) and for all patients receiving propranolol (p less than 0.01). These data demonstrate a modest reduction of infarct size with intraoperative propranolol as an adjunct to our standard management of patients having aortic cross-clamping. Quantitation of creatine kinase MB release is the best clinically available method for assessing alterations in techniques of myocardial preservation.