Increased administration of oxygen improves cerebral oxygenation during carotid endarterectomy

Abstract

Creation of an arteriovenous fistula is a common vascular procedure in patients with significant co-morbidities. Brachial plexus block is a safe alternative to general anaesthesia in these patients [1]. It has been shown that the regional sympathetic block associated with brachial plexus block produces a greater increase in brachial artery blood flow than general anaesthesia with less systemic hypotension [2]. Therefore we hypothesised that the favourable peri-operative haemodynamics under brachial plexus block may influence the rates of fistula patency. MethodsA prospective database of access surgery was used to identify 107 patients who had proximal radiocephalic, brachiocephalic and basilic transposition fistulas under general anaesthesia (n ¼ 75) or brachial plexus block (n ¼ 32) between 2003 and 2006. Anaesthetic technique was at the discretion of the anaesthetist at the time of surgery. Primary and secondary patency of the fistula and patients' survival are reported using Kaplan-Meier survival analysis (reported as cumulative outcomes at 12 months) and compared by the log rank test. ResultsPrimary failure occurred in 3/32 (9%) patients with brachial plexus block compared to 13/75 (17%) with general anaesthesia, although this did not reach statistical significance. There was an improvement in cumulative secondary patency in the brachial plexus block group compared to general anaesthesia (0.906 vs 0.597, respectively; p ¼ 0.04 (Fig. 1)). However, there was no difference in cumulative primary patency (0.574 vs 0.450; p ¼ 0.38) or cumulative patient survival (0.947 vs 0.696; p ¼ 0.99). DiscussionWe found a statistically significant improvement in the secondary patency of fistulae created under brachial plexus block compared with general anaesthesia. The optimum haemodynamics under brachial plexus block may be responsible for this effect. Other mechanisms may include prevention of chronic activation of the sympathetic nervous system. Brachial plexus block is a safe alternative to general anaesthesia that may offer benefits beyond the peri-operative period.

Cerebral oximetry during carotid clamping: is blood pressure raising necessary?

“…As a matter of explanation, an assumption is made that ipsilateral cerebral tissues are oxygen delivery dependent more than contralateral districts. Supporting this hypothesis, de Beer et al [12] reported that giving 100% oxygen during the clamping phase improves cerebral oxygenation without raising blood pressure. Our objection is that the choosing f i O 2 100% during carotid clamping may mask a deficit of perfusion in the non-monitored brain districts, giving a normal rSO 2 in the frontal lobes.…”