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

OBJECTIVES: 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.

DESIGN: Prospective, non-randomised, observational study.

MATERIALS: Sixty-five consecutive patients (33 RA; 32 GA) undergoing carotid endarterectomy.

METHODS: (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.

RESULTS: 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).

CONCLUSIONS: 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.