Effect of carotid revascularization on cerebral autoregulation in combined cardiac surgery†

Abstract

Objectives: Combined carotid artery endarterectomy (CEA) and coronary artery bypass grafting surgery is considered to reduce long-term stroke risk for patients with severe carotid artery stenosis. The benefits of CEA for improving cerebral perfusion during subsequent cardiopulmonary bypass (CPB) are unclear. The purpose of this pilot study was to assess cerebral autoregulation and cerebral oximetry in patients undergoing combined CEA and cardiac surgery with those undergoing cardiac surgery without significant carotid artery stenosis or with uncorrected stenosis.

Methods: Cerebral autoregulation was monitored continuously in 257 patients with the cerebral oximetry index (COx). COx represents a moving Pearson's correlation coefficient between low-frequency changes in regional cerebral oxygen saturation (rScO2) and mean arterial pressure that has been validated in previous investigations. Impaired autoregulation was defined as a value of COx ≥0.3.

Results: Nineteen patients had prior CEA, 8 underwent combined CEA and cardiac surgery, 8 had uncorrected stenosis >70% and 197 had stenosis <50%. Combined, patients with stenosis >70% had a higher COx before CPB compared with those with stenosis <50% (median, 0.26, 25th percentile and 75th percentile [p25-p75], 0.18-0.33 vs 0.18, p25-p75, 0.07-0.27, respectively, P = 0.054). Patients who underwent combined CEA and cardiac surgery had a higher COx before surgery compared with those with prior CEA (P = 0.027) and stenosis <50% (P = 0.026). There were no differences in average COx or rScO2 during CPB in patients undergoing combined CEA and cardiac surgery compared with those with prior CEA (P = 0.53, 0.27) and those with stenosis <50% (P = 0.71, 0.19), respectively. During CPB, patients with uncorrected stenosis had an average COx of 0.36 (p25-p75, 0.28-0.56) indicating cerebral autoregulation impairment, and lower rScO2 compared with patients with prior CEA (P = 0.006) and stenosis <50% (P = 0.005).

Conclusions: While higher at baseline, patients undergoing CEA immediately before cardiac surgery had COx and rScO2 measurements during CPB similar to those with non-significant stenosis in contrast to those patients with uncorrected stenosis who had evidence of impaired autoregulation and lower rScO2. These preliminary results suggest the potential utility of COx, possibly for complimenting patient selection for CEA as well as for individual patient management during surgery.

Keywords: Cardiopulmonary bypass; Carotid endarterectomy; Cerebral autoregulation; Cerebral oximetry.