Spread of injectate associated with radial or median nerve-type motor response during infraclavicular brachial-plexus block: an ultrasound evaluation.
OBJECTIVE
We have compared ultrasound characteristics of spread during infraclavicular brachial-plexus blocks by use of electrically evoked radial-nerve- or median-nerve-type distal motor responses to guide the injection of 30 mL of 1.5% mepivacaine.


METHODS
Consecutive patients who required surgery distal to the upper arm were prospectively included in this study. With radial- or median-evoked distal motor response at a stimulating current intensity of less than 0.5 mA, patients were distributed into 2 equal groups. An independent investigator blinded to the evoked response described ultrasound characteristics of the spread of local anesthetic and assessed block quality 30 minutes after placement. A quality diffusion score proportional to the extent and intensity of spread around the axillary artery was used, and dynamic movements during injection were noted.


RESULTS
Thirty-two patients were included. With radial-nerve-type motor response, the success rate of infraclavicular plexus block was 100%, but 3 supplemental axillary blocks were requested with median-nerve-type motor response. Quality diffusion scores were significantly higher with radial-nerve-type as compared with median-nerve-type motor response (P = .03). Injection after radial-nerve-type motor response resulted in a typical and reproducible ultrasound feature of posterior local-anesthetic spread associated with medial and upper movement of the axillary artery. With median-nerve-type motor response, failed blocks were associated with a specific posterior displacement of the axillary artery that resulted from superficial spread.


CONCLUSIONS
We have demonstrated that as compared with median-nerve-type motor response, injection performed after a radial-nerve-type motor response promoted reproducible and remarkable ultrasound spread characteristics associated with complete sensory block of the 3 cords at 30 minutes.
Bloc
Sébastien
S
Department of Anesthesiology, Private Hospital, Claude Galien, Quincy-sous-Snart, Paris, France.
Garnier
Thierry
T
Komly
Bernard
B
Asfazadourian
Hugues
H
Leclerc
Pascal
P
Mercadal
Luc
L
Morel
Bertrand
B
Dhonneur
Gilles
G
D000328:Adult; D000368:Aged; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000493:pharmacokinetics; D001365:Axilla; D001917:Brachial Plexus / Q000187:drug effects; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D006801:Humans; D007267:Injections; D008297:Male; D008475:Median Nerve / Q000187:drug effects / Q000502:physiology; D008619:Mepivacaine / Q000008:administration & dosage / Q000493:pharmacokinetics; D008875:Middle Aged; D009407:Nerve Block / Q000009:adverse effects* / Q000295:instrumentation; D011446:Prospective Studies; D011826:Radial Nerve / Q000187:drug effects / Q000502:physiology; D018084:Ultrasonography, Interventional
D000779:Anesthetics, Local; D008619:Mepivacaine