[Tolerance and efficacy of peripheral nerve blocks for carpal tunnel release].

INTRODUCTION: Several peripheral nerve block techniques (PNB) are performed for hand surgery. Their tolerance by patients or their efficacy are poorly described. We evaluated them for blocks at the wrist and at the brachial canal.

PATIENTS AND METHODS: Cohort of outpatients undergoing open carpal tunnel release under PNB with arm tourniquet. Various anaesthetic protocols existed in our staff. The primary end points were a moderate to severe pain (greater than 3/10 on a numerical rating scale) felt during needle puncture, nerve stimulation, mepivacaine injection, at the surgical site (intraoperatively) or at the arm tourniquet, an intraoperative lidocaine supplementation, the occurrence of vasovagal events. For each primary end point, a logistic regression analyzed: the effects of gender, age, operated side, Emla(®)application, sedation before PNB (midazolam-sufentanil), wrist or brachial canal approach, musculocutaneous or radial block were using.

RESULTS: Between January 2007 and June 2010, 551 consecutive patients were analyzed. Puncture pain, mepivacaine injection pain, pain tourniquet and vasovagal events were associated with wrist block (P=0.003, relative risk=1.86; P<0.001, RR=4.22; P<0.001, RR=4.52; P=0.035, RR=6.40). An intraoperative pain greater than 3/10 at the surgical site, or a supplementation by the surgeon were associated with the absence of musculocutaneous block (P=0.013, RR=2.44; P=0.013, RR=2.51).

DISCUSSION: Wrist blocks are less tolerated than brachial canal blocks. The musculocutaneous nerve might often participate in the palm sensitive innervation. For open carpal tunnel release, median, ulnar and musculocutaneous nerves blocks at the brachial canal should be preferred.