A comparison of four stimulation patterns in axillary block.

Abstract

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). 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. 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. 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.