A comparison of four stimulation patterns in axillary block

BACKGROUND AND OBJECTIVES: Insufficient spread of the local anesthetic toward the retroarterial region of the neurovascular space may be responsible for inconsistent anesthesia of the upper limb after single-injection axillary block. We hypothesized that injection of the local anesthetic on a single radial-nerve stimulation would produce the same extent of anesthesia as either a single median-nerve stimulation, a double-stimulation technique (radial and musculocutaneous nerves), or a triple-stimulation technique (radial, musculocutaneous, and median nerves). METHODS: One hundred twenty patients were randomly assigned to receive an axillary block by either median-nerve, radial-nerve, radial-nerve plus musculocutaneous-nerve, or triple-nerve stimulation with 40 mL of plain 1.5% mepivacaine. Patients were assessed for sensory block by the pinprick method at 5 and 20 minutes. RESULTS: Radial-nerve stimulation produced more extensive anesthesia than did median-nerve stimulation. The rate of anesthesia at 20 minutes in the median-nerve cutaneous distribution was similar after median-nerve stimulation or radial-nerve stimulation. The ulnar nerve was more frequently blocked at 20 minutes after radial-nerve stimulation than after median-nerve stimulation. Extent of anesthesia at 20 minutes after radial-nerve plus musculocutaneous-nerve stimulation was similar to that produced by triple-nerve stimulation, except for lower rates of anesthesia that corresponded to the median nerve. All of the differences were statistically significant. CONCLUSIONS: Musculocutaneous-nerve stimulation and radial-nerve stimulation play predominant roles in the success of axillary brachial plexus block, although a triple-nerve stimulation technique is still required to produce complete anesthesia of the upper limb.