Does Off-Pump Coronary Artery Bypass Surgery Reduce the Risk of Brain Injury?

(#2000-09999)

David A. Stump, PhD, Kashemi D. Rorie, PhD, Tim J.J. Jones, FRCS

Department of Anesthesiology, Wake Forest University School of Medicine, Winston-Salem, North Carolina

ABSTRACT

Documented evidence indicates that cardiopulmonary bypass (CPB) is an independent risk factor for end organ injury, particularly brain injury, following heart surgery. Because CPB and aortic cannulation are not performed during off-pump coronary artery bypass (OPCAB), it is expected that the incidence of brain injury attributable to these factors should be reduced with OPCAB. The mechanisms contributing to post-CPB neuropsychological deficits are uncertain. However, three major interrelated etiologic factors, hypo-perfusion, the systemic inflammatory response, and embolism are obvious suspects.

It is assumed that coronary artery bypass graft (CABG) surgery without CPB will diminish the potential for emboli. In essence, the avoidance of CPB during CABG surgery would be expected to reduce cerebral injury by reducing the cerebral embolic load, resulting in improved clinical outcomes. The number of ultrasonically detectable macroemboli delivered to the brain is the best predictor of neurobehavioral deficits. This article considers the results of studies indicating that a substantial portion of microemboli result from shed blood being reinfused via the CPB circuit.

Despite these expectations, recent studies examining the cerebroprotective effect of OPCAB procedures versus conventional coronary artery bypass (CCAB) have yielded inconsis-tent results. This article reviews the results of some of these studies and concludes that, collectively, the studies identify no clear superiority of either the OPCAB or the CCAB technique. Instead, they clearly suggest that patients undergoing these two procedures are not clinically similar. Whether the differences are due to the avoidance of CPB, patient selection bias, or a reduction in the number of coronary anastomoses in OPCAB patients remains unclear.

Until systematic, blinded, prospective studies are conducted comparing CABG with and without CPB, it cannot be positively concluded that CPB is an independent risk factor of cerebral complications following heart surgery. Although specific CPB components may be associated with increased risk of brain injury, it may be that other factors independent of CPB (e.g., blood product utilization or aortic manipulation) may impart a greater independent risk than CPB alone.

AUTHOR/ARTICLE INFORMATION

Address correspondence and reprint requests to: David A. Stump, PhD, Department of Anesthesiology, Wake Forest University School of Medicine, Winston-Salem, NC, 27157-1009; Phone: (336) 716-2329; Fax: (336) 716-3909; Email: dstump@wfubmc.edu.

Key Words: CABG, CPB, OPCAB, CCAB, neurobehavioral deficits, post-operative cognitive dysfunction, cerebral macroemboli, cerebral microemboli, reinfusion of shed blood