AANA Journal /February 2004/Vol. 72, No. 1 57 T he transarterial approach to axillary brachial plexus block is a well-established method of producing regional anesthesia for surgeries at or below the elbow. 1-4 The transarterial approach is technically less difficult and reportedly results in a more reliable block compared with other approaches. 2-6 The reported failure rate of the transarterial approach, however, remains 20% to 30%. 2,3 It has been suggested in clinical trials that fail- ure of the transarterial approach may be secondary to injection of the local anesthetic outside the neurovas- cular sheath. 2,3 Cockings et al 3 provided clinical evi- dence suggesting that failure of the brachial plexus block using the axillary transarterial approach is com- monly due to advancement of the needle beyond the posterior wall of the neurovascular sheath. A 22- gauge, 1 1 / 2 -in, B bevel needle frequently is used for transarterial brachial plexus block. The failure rate at our institution using a 1 1 / 2 -in needle is similar to the 20% to 30% reported in the literature. The transarterial approach to brachial plexus block is a well-established method of producing anesthesia of the upper extremity. However, it is associated with a failure rate of 20% to 30%. Failure may be secondary to the common use of a relatively long needle, which can penetrate the posterior wall of the sheath and result in inadvertent injec- tion of the local anesthetic into the surrounding tissue. The purpose of this investigation was to compare success rates following transarterial brachial plexus block with a stan- dard 22-gauge, 1 1 / 2 -in, B bevel needle or a 26-gauge, 1 / 2 -in needle. We enrolled 98 subjects scheduled for elective surgery at or below the elbow and randomized them into 2 groups. The control group received a transarterial axillary block with a standard 22-gauge, 1 1 / 2 -in, B bevel needle, and the experi- mental group received a transarterial axillary block with a 26-gauge, 1 / 2 -in needle. Success was defined as no discom- fort at the time of incision. Success rates were compared using a c 2 test, and a P value of less than .05 was considered significant. The overall success rate was significantly higher with the 26-gauge, 1 / 2 -in needle (42/48 [88%]) than with the 22-gauge, 1 1 / 2 -in needle (39/49 [69%]; P = .035). Key words: Needle size, regional anesthesia, transarterial brachial plexus block, success rate. Effect of needle size on success of trans- arterial axillary block LCDR Lorraine A. English, CRNA, MS, NC, USN Okinawa, Japan LT Johnnie M. Holmes, CRNA, MS, NC, USN Camp Lejeune, North Carolina LCDR Joseph F. Burkard, CRNA, MS, NC, USN San Diego, California CAPT Charles A. Vacchiano, CRNA, PhD, NC, USN Pensacola, Florida Alexander Shin, MD Rochester, Minnesota CDR Joseph Pellegrini, CRNA, DNSc, NC, USN LCDR John P. Maye, CRNA, PhD, NC, USN Bethesda, Maryland In 1961, DeJong 5 published a report describing the use of a 26-gauge, 1 / 2 -in needle for transarterial axil- lary brachial plexus block. DeJong suggested the shorter needle was of ample length to penetrate the neurovascular sheath but not long enough to pierce the posterior wall of the sheath, regardless of the size of the patient. 5 However, DeJong did not reveal whether the use of this shorter needle improved the success rate. A thorough review of the literature revealed no previous study had examined the success rate associated with the use of a short, small-caliber needle. The purpose of this study was to compare the success rates following transarterial brachial plexus block using a 26-gauge, 1 / 2 -in needle or a standard 22- gauge, 1 1 / 2 -in, B bevel needle. Materials and methods The study was conducted in the main operating room of the Naval Medical Center, San Diego, Calif, follow- ing institutional review board approval. Informed