Comparison of the effect of on-pump and off-pump coronary artery bypass grafting on neurological events

Cerebral injury has been a recognized complication of cardiac surgery since the 1950s [1] and is still the most significant and disabling complication of coronary artery bypass grafting (CABG). Although cerebral injury also occurs after major non-cardiac surgical procedures [2], it is more common and severe after operations using cardiopulmonary bypass (CPB), supporting the potentially deleterious effects of extracorporeal circulation. Over the last decade, improvements in anaesthetic and surgical techniques, as well as in postoperative management, have resulted in a reduction in mortality following CABG. This, however, has not been paralleled by a reduction in cerebral injury, as patients with a higher risk profile increasingly constitute the surgical population. Cerebral injury can be broadly classified, in decreasing order of severity but increasing incidence, as stroke, delirium (encephalopathy) and neurocognitive dysfunction. The aetiology of postoperative cerebral injury is multifactoral. Stroke is largely caused by embolic debris during aortic manipulation while delirium and neurocognitive dysfunction are more closely linked with the use and conduct of CPB. CPB has three main pathophysiological mechanisms: gaseous and solid cerebralmicroembolization, intraoperative hypotension and/or hypoperfusion and the systemic inflammatory response syndrome [3]. Intraoperative cerebral microembolization is probably the most important mechanism [4, 5]. Brown and colleagues demonstrated large numbers of lipidmicroemboli in the brains of patients who died after cardiac surgery and whose numbers correlated with the duration of CPB [5]. Recently we have confirmed the occurrence of both gaseous and particulate cerebral microemboli during CPB and that both are substantially reduced with off-pump CABG [6]. This chapter explores current concepts of the incidence, pathophysiology and prevention of cerebral injury in on-pump and off-pump surgery. © Springer-Verlag Berlin Heidelberg 2006.