DEEP OR SUPERFICIAL CERVICAL PLEXUS BLOCK FOR CAROTID ENDARTERECTOMY

Abstract

106 Introduction At many institutions, including ours, carotid endarterectomy (CEA) is performed awake under cervical plexus block (CPB) using the patient's neurologic status as a continuous monitor of cerebral perfusion. A combination of deep and superficial CPB, with local supplementation of 1% lidocaine (LA) as required by the surgeon is used. Complications of deep CPB, particularly phrenic nerve palsy, which occurs in 60% of patients [1] and potential subarachnoid or vertebral artery injection may contraindicate its' use occasionally. In such patients, we have used superficial CPB alone to provide successful anesthesia. We hypothesized that superficial CPB is as effective as deep block for CEA surgery and compared the two in a prospective, randomized controlled trial. Methods Following ethics committee approval, 40 patients presenting for CEA gave written consent and were randomized to receive either a single-injection deep CPB at C4 [2] or a superficial CPB [3], both using 20 ml 0.375% bupivacaine. Blocks were assessed after 20 minutes by an anesthesiologist blinded as to which block had been placed. The main outcome measure was additional LA (1% lidocaine) given superficially or deep by the surgeons, who were also blinded to the type of block. The power calculation was based on showing 4 ml additional LA difference between the 2 groups. We also looked at: dermatomes affected by the block; paresthesia during CPB placement; muscle relaxation; time to first analgesia and visual analogue pain scores. Sedation with diazepam was titrated to effect but no IV analgesia was given. Post-operative analgesic requirements were assessed by recovery nurses blinded to the study and morphine or acetominophen given accordingly. Results All blocks were adequate for surgery to proceed. Seven patients in the deep group had demonstrable C5 sensory changes after the block. Median total additional LA were 6 (range 0.5-20) ml in the deep group and 6 (range 0-20) ml in the superficial group (Mann-Whitney U test, p=0.732). Patients receiving deep CPB who reported paresthesia during block placement (n=12) required less LA (median 2, range 0.5-20 ml) than those who did not report paresthesia (n=8) (median 9.5, range 6-15.5 ml) (Mann-Whitney U test, p=0.011). There were no differences in surgical exposure as assessed by the surgeons. Patients receiving deep blocks were less likely to need analgesia postoperatively (Table 1).Table 1: Analgesic requirements in the first 24 h after CEAConclusion CEA may be performed effectively under superficial CPB alone without the need for deep block. Although there were different analgesic requirements of the two groups, the serious potential complications of deep block may be avoided in patients with respiratory compromise by the use of superficial CPB alone. Actively seeking paresthesia when performing deep CPB increases its effectiveness.