Single stimulation of the posterior cord is superior to dual nerve stimulation in a coracoid block

BACKGROUND: Both multiple injection and single posterior cord injection techniques are associated with extensive anesthesia of the upper limb after an infraclavicular coracoid block (ICB). The main objective of this study was to directly compare the efficacy of both techniques in terms of the rates of completely anesthetizing cutaneous nerves below the elbow. METHODS: Seventy patients undergoing surgery at or below the elbow were randomly assigned to receive an ICB after the elicitation of either a single radial nerve-type response (Radial group) or of two different main nerve-type responses of the upper limb, except for the radial nerve (Dual group). Forty milliliters of 1.5% mepivacaine was given in a single or a dual dose, according to group assignment. The sensory block was assessed in each of the cutaneous nerves at 10, 20 and 30 min. Block performance times and the rates of complete anesthesia below the elbow were also noted. RESULTS: Higher rates of sensory block of the radial nerve were found in the Radial group at 10, 20 and 30 min (P<0.05). The rates of sensory block of the ulnar nerve at 30 min were 97% and 75% in the Radial and in the Dual groups, respectively (P<0.05). The rate of complete anesthesia below the elbow was also higher in the Radial group at 30 min (P<0.05). CONCLUSIONS: Injection of a local anesthetic after a single stimulation of the radial nerve fibers produced more extensive anesthesia than using a dual stimulation technique under the conditions of our study.