Comparison of axillary block techniques: is there a difference in success rates?

This study compared the success rates between two accepted methods of performing axillary blocks, the peripheral nerve stimulator (PNS) and the transarterial (TA) techniques. Success was based on blocking the nerves involved in the surgery. Following institutional review board approval and informed consent, 57 patients between the ages of 18 and 86 years of age scheduled for elective upper extremity surgery were studied. Patients were randomized and all blocks were performed according to the protocol for PNS and TA techniques using the dosage of local anesthetic based on patient weight. All patients were premedicated with fentanyl hydrochloride, 1 microgram/kg, and midazolam, 1 to 5 mg. Scoring was accomplished on a standardized form by one of two physicians, unaware of the technique, for 5 of the major nerves at 20 and 30 minutes after injection. Sensory blockade was determined by pinprick. Motor blockade was assessed according to a scale ranging from complete block to no effect. Two of the patients had vascular procedures, and the remainder were orthopedic procedures. There were no differences in the effectiveness on the musculocutaneous, radial, median, or ulnar nerves. There was a significant difference (P < 0.05) in the effectiveness at the axillary nerve. The transarterial technique was 66% effective as opposed to 47% for the PNS. There was no difference in the need for local supplementation or general anesthesia between the two groups. There were no significant side effects reported by the patients postoperatively. The axillary nerve was the only nerve with an increased success rate using the TA technique. This indicates that both techniques are equally acceptable.