Increased success rate with infraclavicular brachial plexus block using a dual-injection technique.

STUDY OBJECTIVE: To test the hypothesis that dual injection of the local anesthetic in coracoid infraclavicular brachial plexus block might enhance both sensory and motor block for anesthesia of the upper limb when compared with a single-injection technique.

DESIGN: Comparative, prospective, randomized, investigator-blinded study.

SETTING: University-affiliated hospital.

PATIENTS: 60 patients scheduled for surgery of the hand, forearm, or elbow.

INTERVENTIONS: Patients were randomly assigned to receive either a coracoid infraclavicular block guided by nerve stimulator with a single injection technique (Group 1) or a dual-injection technique (Group 2). Injection of 40 mL 1.5% mepivacaine was made after eliciting one evoked motor response in the upper limb with a nerve stimulator for coracoid infraclavicular block in Group 1 and injection of two separate doses of 20 mL 1.5% mepivacaine after elicitation of two motor responses in Group 2.

MEASUREMENTS: Assessment of sensory and motor block in the upper limb 5 and 20 minutes after the end of the injection of the local anesthetic. The time needed to elicit the second response and to inject the second dose of local anesthetic was also recorded.

MAIN RESULTS: Significantly higher rates of sensory block to pinprick on the distributions of axillary, musculocutaneous, radial, ulnar, and medial cutaneous of the forearm nerves were found in Group 2 at 20 minutes. Significantly higher rates of motor block for arm, wrist, and hand movements were found in Group 2 at 20 minutes.

CONCLUSIONS: Dual injection of local anesthetic guided by nerve stimulator increases the efficacy of coracoid block when compared with a single injection of the same dose of local anesthetic.