Does off-pump coronary artery bypass surgery reduce the risk of brain injury?

Documented evidence indicates that cardiopulmonary bypass (CPB) is an indep endent risk factor for end organ injury, particularly brain injury, followi ng heart surgery. Because CPB and aortic cannulation are not performed duri ng off-pump coronary artery bypass (OPCAB), it is expected that the inciden ce of brain injury attributable to these factors should be reduced with OPC AB. The mechanisms contributing to post-CPB neuropsychological deficits are uncertain. However, three major interrelated etiologic factors, hypo-perfu sion, 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 du ring CABG surgery would be expected to reduce cerebral injury by reducing t he cerebral embolic load, resulting in improved clinical outcomes. The numb er of ultrasonically detectable macroemboli delivered to the brain is the b est predictor of neurobehavioral deficits. This article considers the resul ts of studies indicating that a substantial portion of microemboli result f rom 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 inconsistent results. This article reviews the results of so me of these studies and concludes that, collectively, the studies identify no clear superiority of either the OPCAB or the CCAB technique. Instead, th ey clearly suggest that patients undergoing these two procedures are not cl inically similar. Whether the differences are due to the avoidance of CPB, patient selection bias, or a reduction in the number of coronary anastomose s 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 ind ependent risk factor of cerebral complications following heart surgery. Alt hough specific CPB components may be associated with increased risk of brai n injury, it may be that other factors independent of CPB (e.g., blood prod uct utilization or aortic manipulation) may impart a greater independent ri sk than CPB alone.