The differing effects of regional and general anaesthesia on cerebral metabolism during carotid endarterectomy

Abstract

To examine the effects of either regional (RA) or general (GA) anaesthesia upon parameters of cerebral metabolism (near infrared spectroscopy, continuous jugular venous oximetry) during carotid endarterectomy. Prospective, non-randomised, observational study. Sixty-five consecutive patients (33 RA; 32 GA) undergoing carotid endarterectomy. (i) Near infrared spectroscopy: measurement of concentrations of cerebral oxyhaemoglobin (HbO2), deoxyhaemoglobin (HHb) and oxidised cytochrome oxidase (caa3). (ii) Continuous jugular venous oximetry: O2 saturation of jugular venous blood (SJvO2). (iii) Stump pressure in internal carotid artery. A reduction in SJvO2 (RA: 13% (95% CI-3 to 29%) GA: 9% (95% CI-2 to 20%), p < 0.08) and a fall in caa3 levels (RA vs. GA: 25/31 vs. 19/31, p = 0.2) was more likely in patients given a RA following application of the carotid clamps. When HbO2 and caa3 did fall however spontaneous recovery occurred more often (RA vs. GA; caa3: 18/25 vs. 5/19, p < 0.005; HbO2: 30/31 vs. 4/28, p < 0.001). Although GA may offer a degree of cerebral protection by reducing cerebral metabolic rate (lower falls in SJvO2 and caa3) RA preserved cerebral autoregulation as judged by the spontaneous recovery in caa3 and HbO2 levels.