A comparison of proximal and distal radial nerve motor responses in axillary block using triple stimulation.
OBJECTIVE
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Sia
Salvatore
S
Department of Anesthesiology, Centro Traumatologico Ortopedico, Azienda Ospedaliera Careggi, Via Santelli 41, 50134 Florence, Italy. sia3@interfree.it
Lepri
Antonella
A
Magherini
Manuela
M
Doni
Lorenzo
L
Di Marco
Pietro
P
Gritti
Gaetano
G
D000328:Adult; D000779:Anesthetics, Local / Q000008:administration & dosage; D001917:Brachial Plexus / Q000187:drug effects; D002045:Bupivacaine / Q000008:administration & dosage; D004311:Double-Blind Method; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D006801:Humans; D008012:Lidocaine / Q000008:administration & dosage; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D009407:Nerve Block / Q000009:adverse effects / Q000379:methods*; D010147:Pain Measurement / Q000379:methods; D011446:Prospective Studies; D011826:Radial Nerve / Q000187:drug effects*; D013997:Time Factors; D034941:Upper Extremity / Q000601:surgery
D000779:Anesthetics, Local; D008012:Lidocaine; D002045:Bupivacaine