Block of the brachial plexus branches by the humeral route. A prospective study in 503 ambulatory patients. Proposal of a nerve-blocking sequence.

BACKGROUND: Brachial plexus is usually approached by the supraclavicular or axillary route. A technique for selective blockade of the branches of the plexus at the humeral canal using electrolocation has recently been proposed. The aim of the present study was to assess the feasibility of this technique in the ambulatory patient and to determine the optimal sequence of nerve-blocking.

METHODS: The nerves originating from the brachial plexus were located in the humeral canal, at the junction of the proximal and the middle third of the arm, with a stimulator and blocked using either lidocaine or a mixture of lidocaine and bupivacaine, depending on the anticipated duration of surgery. The minimal stimulating intensity eliciting an adequate response, type of local anaesthetic and injected volume, and time of onset of surgical anaesthesia were collected.

RESULTS: The study included 503 consecutive ambulatory patients due to undergo surgery of the elbow, wrist or hand in one year. Suitable anaesthesia was obtained with the humeral blockade in 82.1% of cases. In the remaining 17.9%, an additional block at the elbow was required, mainly for ulnar and median nerves. The onset times of sensory blocks were the longest for the median nerve, similar for the radial and ulnar nerves, shorter for the musculocutaneous nerve and the shortest for the medial brachial and antebrachial cutaneous nerves. The difference was more significant with the lidocaine-bupivacaine mixture, than with lidocaine alone (P<0.001 vs P<0.05, respectively). The onset times of motor blocks were the longest for the median nerve (P<0.05) and the shortest for the musculocutaneous nerve (P<0.001). Neither nervous nor vascular complications occurred.

CONCLUSION: This study shows that the nerve block at the humeral canal is an efficient and safe technique. Considering the onset times of nerve blocks, the following sequence for blockade can be recommended: median, ulnar, radial, musculocutaneous, medial (brachial and antebrachial) cutaneous nerves. The selective blockade of the main nerves of the upper limb at the humeral canal can be recommended for surgery of the forearm and the hand in the ambulatory patient.