Reducing the Risk of Myocardial Revascularization: Relevance of Multimodal Brain Monitoring

Abstract

Perioperative neurologic events in heart surgery are the most devastating complications. Although myocardial revascularization without cardiopulmonary bypass (CPB) has reduced the incidence of cerebrovascular accidents, they still remain a reality that the cardiothoracic surgeon is unable to completely eliminate. The events leading to a neurologic complication are related to hemodynamic instability and embolization of aortic debris at the time a side-biting clamp is applied. Combined events may eventually impact the brain to varying degrees, ranging from a temporary confusional state to a full-blown stroke from which meaningful recovery may be impossible. This report describes the interventions necessary to maintain hemodynamic stability, the role of brain monitoring required, and how to safely achieve complete off-CPB myocardial revascularization and minimize the incidence of neurologic complications. Cardiac interventions include maintaining sinus rhythm, providing adequate blood supply to all vital organs, and avoiding induction of myocardial ischemia, which may induce supraventricular, ventricular arrhythmias, or both. These interventions depend upon an experienced surgical team (anesthesiologist, cardiologist, surgeon, and operating room and intensive care unit recovery nurses). Anticipation of myocardial ischemia may require loading the patient with antiarrhythmic drugs, and placement of intracoronary shunts and intraaortic balloon pump support. Patience from the surgeon is often required to allow time for the specific intervention to act. In addition to interventions to maintain a balance between the demand and supply of oxygen, we frequently rely on "intermittent hypotensive anesthesia'' while performing the distal and proximal coronary anastomoses. Hypotension may lead to inadequate oxygen supply to the brain, so multimodal brain monitoring becomes mandatory. We use a combination of transcranial brain oximetry and electroencephalographic compressed spectral array. This combined monitoring results in a safer surgical procedure, allowing the hemodynamic interventions to be performed rationally and without interruption of the surgical procedure.