Adverse neurologic events: risks of intracardiac versus extracardiac surgery

Abstract

Intracardiac operations such as valve replacements have typically carried a higher risk (4.2% to 13%) of overt central nervous system outcome, compared with coronary artery bypass grafting (CABG) procedures (0.6% to 5.2%). This is likely owing to the increased risk of macroembolization of air or particulate matter from the surgical field during intracardiac surgery. The periods of highest risk for emboli are during aortic cannulation and especially during release of aortic clamps and weaning from bypass. The number of embolic events measured with transcranial Doppler is significantly higher in patients undergoing valve surgery compared with coronary surgery, particularly during cardiac ejection and immediately after bypass. However, there is current evidence that neurologic risk is increasing in patients undergoing CABG owing to the tendency to operate on older patients with more severe aortic atherosclerosis and cerebrovascular disease. Patients having an intracardiac procedure combined with a CABG procedure may be at particularly high risk for adverse neurologic outcome. For all cardiac surgical patients, there is some cause for optimism in that risk may be minimized by improved assessment (e.g., intraoperative transesophageal or epiaortic echocardiographic scanning of the ascending aorta to identify patients at risk) and monitoring (e.g., detection of embolic phenomena, using transesophageal echocardiography or transcranial Doppler technology). Furthermore, in the future, development and testing of more ideal cerebroprotective drugs may allow amelioration of neurologic injury, either by pretreating all patients at risk, or possibly even by delaying treatment until after the suspected occurrence of an insult.