Differences in cognitive function and S100 production after carotid endarterectomy under local or general anaesthetic

Background: Previous studies reported both improved (enhanced cerebral perfusion after carotid endarterectomy (CEA)) and diminished (intraoperative ischaemic injury) cognitive function (CF) following CEA. These studies were not adequately controlled for anxiety, general health and learning (repeated testing), and the influence of anaesthetic technique was not assessed. Methods: This study assessed CF (trained psychologist, seven computerized tests) before operation, and at 5 and 90 days after CEA performed under local anaesthesia (LA) (n = 34) or general anaesthesia (GA) (n = 13). Similar measurements in patients undergoing lower limb revascularization (n = 14) and unoperated subjects with asymptomatic carotid stenosis greater than 70 per cent (n = 16) tested twice, 3 months apart, controlled for the effects of anaesthesia, surgery and carotid arteriosclerosis. Additionally, jugular venous S100 levels (neuronal protein released following cerebral injury) were measured (before carotid clamping, and 1, 4 and 24 h after clamp release) in 18 of these patients (nine LA, nine GA). Results: Compared with controls, test performance in patients who had CEA under GA improved in one (executive CF 90 days; P = 0·028), but deteriorated in another (working memory 90 days; P = 0·038) while patients who had LA improved in three of seven tests (executive function, working memory) at 5 days (P = 0·03, 0·048, 0·036) and 90 days (P = 0·01, 0·05, 0·006). Further, a greater than 25 per cent improvement in one or more tests was more likely 90 days after CEA under LA (22 of 34 versus four of 13; P < 0·04) with improved executive function, speed and accuracy. S100 levels were lower after CEA under LA (1 h: 0 (0–30) versus 29 (8–98) µg ml−1, P < 0·05; 4 h: 0 (0–6) versus 22 (2–95) µg ml−1, P < 0·05; 24 h: 0 (0–1) versus 35 (14–77) µg ml−1, P < 0·01). Conclusion: This study demonstrated improved CF following CEA under LA which was associated with lower jugular venous S100 levels (marker of cerebral injury). These differences may reflect improved cerebral oxygenation (preservation of cerebral autoregulation). © 2000 British Journal of Surgery Society Ltd