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EDITORIAL

Metoprolol and Coronary Artery Bypass Grafting Surgery: Does Intraoperative Metoprolol Attenuate Acute ß-Adrenergic Receptor Desensitization During Cardiac Surgery?

John V. Booth, MBChB FRCA^*, Erin E. Ward, BS^*, Kelly C. Colgan, BS, Bonita L. Funk, BS^*, Habib El-Moalem, PhD^*, Michael P. Smith, BS^*, Carmelo Milano, MD, Peter K. Smith, MD, Mark F. Newman, MD^*, and Debra A. Schwinn, MD^*

Departments of *Anesthesiology, Surgery, and Medicine, Duke University Medical Center, Durham, North Carolina, for the Duke Heart Center Perioperative Desensitization Group

Address correspondence to John V. Booth, MB, ChB, FRCA, Box 3094, Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710. Address email to booth006{at}mc.duke.edu

Abstract

Cardiac surgery results in significant impairment of ß-adrenergic receptor (ßAR) function and is a cause of depressed myocardial function after surgery. We previously demonstrated that acute administration of ßAR blocker during cardiopulmonary bypass (CPB) in an animal model of coronary artery bypass grafting (CABG) surgery attenuates ßAR desensitization, whereas chronic oral ß-blockade therapy in patients undergoing CABG surgery does not prevent it. Therefore we hypothesized that acute administration of metoprolol during CABG surgery would prevent acute myocardial ßAR desensitization. A placebo-controlled initial phase (n = 72) was performed whereby patients were randomized to either metoprolol 10 mg or placebo immediately before CPB. Then a second dose-finding study was performed where patients received 20 mg (n = 20) or 30 mg (n = 20) of metoprolol. Hemodynamic monitoring, atrial membrane adenylyl cyclase activity, atrial ßAR density, and postoperative outcomes were measured. All groups showed similar decreases in isoproterenol-stimulated adenylyl cyclase activity (13%–24%). Cardiac output remained similar in all 4 groups throughout the intraoperative and postoperative period. In addition, patients receiving metoprolol 20 or 30 mg had less supraventricular arrhythmias 24 h postoperatively compared with patients receiving metoprolol 10 mg or placebo. Therefore, unlike our previous animal model of CABG surgery, metoprolol did not attenuate myocardial ßAR desensitization.

IMPLICATIONS: We investigated whether IV metoprolol given during cardiac surgery attenuates myocardial ß-adrenergic receptor (ßAR) desensitization. Although metoprolol did not reduce ßAR desensitization, the incidence of supraventricular arrhythmias was reduced by 75% in patients receiving 20 mg or 30 mg metoprolol.

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Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999