Physiological advantages of cerebral blood flow during carotid endarterectomy under local anaesthesia. A randomised clinical trial.
OBJECTIVE: to examine the effects of type of anaesthesia on cerebral blood flow during carotid endarterectomy (CEA). DESIGN: prospective randomised study. METHODS: thirty-four CEA procedures under local anaesthesia (LA) are compared to 33 procedures under general anaesthesia (GA). Mean middle cerebral artery velocity (MCAV(mean)) was monitored using Transcranial Doppler (TCD) and mean arterial pressure (MAP) assessed by continuous intra-arterial blood pressure transducer. RESULTS: pre-op MCAV(mean) and MAP were similar in both groups. Pre-clamp MCAV(mean) was similar in both groups and did not differ from pre-op values. With carotid clamping the MCAV(mean) significantly dropped in both groups. The post-clamp MCAV(mean) was significantly less in the GA group (p < 0.05), and the percentage reduction in MCAV(mean) significantly more for GA procedures (p < 0.05). Pre-clamp MAP was significantly elevated in LA procedures and significantly lowered in GA procedures. Pre-clamp MAP was significant less for GA procedures (p < 0.001). Post clamp MAP did not differ from pre-clamp levels in either group. There was no correlation between MCAV(mean) and MAP. Complication rate, combined death/stroke rates were similar in each group. CONCLUSION: LA CEA is associated with better preservation of the ipsilateral cerebral circulation and increased tolerance of the effects of carotid clamping. Changes in MCAV(mean) cannot be explained by variations in blood pressure between the two techniques.