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-Jive consecutive patients (33 RA;32 GA) undergoing carotid endarterectomy. Methods: (i) Near infrared spectroscopy: measurement of concentrations of cerebral oxyhaemoglobin (HbO(2), deoxyhaemoglobin (HHb) and oxidised cytochrome oxidase (caa(3)). (ii) Continuous jugular venous oximetry: O-2 saturation of jugular venous blood (S)vO(2)). (iii) Stump pressure in internal carotid artery. Results: A reduction in SJvO(2) (XA: 13% (95% CI-3 to 29%) GA: 9% (95% CI-2 to 20%), p < 0.08) and a fall in caa(3) levels (RA vs. GA: 25/31 vs. 19/31, p = 0.2) was move likely in patients given a XA following application of the carotid clamps. When HbO(2) and caa(3) did fall however spontaneous recovery occurred more often (RA vs. GA;caa(3): 18/25 vs. 5/19, p<0.005; HbO(2): 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 SJvO(2) and caa(3)) XA preserved cerebral autoregulation as judged by the spontaneous recovery in caa(3) and HbO(2) levels.