A Comparison of Proximal and Distal Radial Nerve Motor Responses in Axillary Block Using Triple Stimulation

• Published in: Regional anesthesia and pain medicine Vol. 30; no. 5; pp. 458 - 463
• Main Authors: Sia, Salvatore, Lepri, Antonella, Magherini, Manuela, Doni, Lorenzo, Di Marco, Pietro, Gritti, Gaetano
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 01.09.2005; BMJ Publishing Group LTD
• Subjects: Adult; Anesthetic technique; Anesthetics, Local - administration & dosage; Axillary block; Brachial plexus; Brachial Plexus - drug effects; Bupivacaine - administration & dosage; Double-Blind Method; Electric Stimulation - methods; Female; Humans; Lidocaine - administration & dosage; Male; Motor Activity - drug effects; Nerve Block - adverse effects; Nerve Block - methods; Nerve stimulation; Pain Measurement - methods; Prospective Studies; Radial; Radial Nerve - drug effects; Regional; Regional anesthesia; Time Factors; Upper Extremity - surgery; Nerve stimulation; Anesthetic technique; Regional; Axillary block; Radial; Brachial plexus
• ISSN: 1098-7339; 1532-8651
• DOI: 10.1016/j.rapm.2005.06.002

Stimulation of the radial nerve at the axilla may cause either a proximal movement (forearm extension) or distal movements (supination, wrist or finger extension). In the most recent studies on axillary block, only a distal twitch was accepted as valid. However, this approach was based only on clinical experience. The aim of this study was to verify if a proximal motor response can be considered a satisfactory endpoint. This was a prospective, randomized, double-blinded study. One hundred fifty patients received a triple-injection axillary brachial plexus block in which the radial nerve was located by a proximal (group PROX) or a distal motor response (group DIST). Patients were assessed for sensory and motor block of the branches of the radial nerve by a blinded investigator at 5-minute intervals over 30 minutes. An 81% success rate for anesthetizing the sensory distal branches of the radial nerve was seen in group PROX; a significantly higher success rate was recorded in group DIST (95%). The onset time of sensory block for the distal branches of the radial nerve was significantly shorter in group DIST (9.9 ± 6 v 15.4 ± 7 minutes). The time to perform the block was slightly shorter and the localization of the nerve simpler in group PROX. The overall block success rate was not significantly different in the 2 groups. Local anesthetic injection at the proximal radial twitch significantly reduces the efficacy and prolongs the onset time of the radial nerve block. Searching for distal response is significantly more difficult and time consuming than searching for proximal response. However, it does not significantly increase patient discomfort or adverse effects.