Monitoring neuromuscular blockade at the vastus medialis muscle using phonomyography.
OBJECTIVE
The vastus medialis muscle has been recently proposed as a new site for monitoring neuromuscular blockade (NMB). The purpose of this study is to compare NMB at the vastus medialis with the adductor pollicis muscle using phonomyography (PMG).


METHODS
Fifteen patients were enrolled in the study. Anesthesia was induced with remifentanil 0.25 to 0.5 microg x kg(-1) x min(-1), followed by propofol 2 to 2.5 mg(-1) x kg(-1) iv. Analgesia was provided by remifentanil 0.05 to 0.25 microg x kg (-1) x min(-1) iv throughout surgery. A small piezo-electric microphone was attached to the middle of the thenar mass of the right hand to record acoustic signals produced by the contraction of the adductor pollicis muscle. A second microphone was fixed to the medial part of the thigh, 10 cm over the patella, to record the response from the vastus medialis muscle. The ulnar nerve and the im branches of the femoral nerve were stimulated using train-of-four stimulation every 12 sec. Onset, maximum effect, and offset of neuromuscular block were measured after mivacurium 0.2 mg x kg(-1) iv and compared.


RESULTS
At the vastus medialis muscle, the onset of NMB was significantly shorter at 1.9 +/- 0.6 min vs 2.8 +/- 0.7 min, the maximum effect less pronounced at 85 +/- 11% vs 96 +/- 2% and recovery of NMB to 25%, 75%, 90% of twitch control height more rapid than at the adductor pollicis muscle at 17 +/- 2.2 min vs 21.6 +/- 4.2 min, 26.7 +/- 6.5 vs 21 +/- 4.1 min and 30.7 +/- 6.6 vs 35.9 +/- 7.1 min, respectively.


CONCLUSIONS
PMG can be used to measure NMB at the vastus medialis muscle. We found a shorter onset time, less pronounced maximum effect and more rapid recovery of NMB at the vastus medialis muscle than at the adductor pollicis muscle.
Michaud
Guillaume
G
Neuromuscular Research Group (NRG), Department of Anesthesiology, Centre Hospitalier de l'Université de Montréal (CHUM) Hôtel-Dieu, Université de Montréal, Montréal, Québec, Canada.
Trager
Guillaume
G
Deschamps
Stéphane
S
Hemmerling
Thomas M
TM
D000328:Adult; D000768:Anesthesia, General; D004558:Electric Stimulation; D005260:Female; D006225:Hand / Q000294:innervation; D006801:Humans; D007546:Isoquinolines; D008297:Male; D008875:Middle Aged; D000077590:Mivacurium; D016343:Monitoring, Intraoperative; D018482:Muscle, Skeletal / Q000187:drug effects*; D009213:Myography; D019148:Neuromuscular Blockade; D003473:Neuromuscular Nondepolarizing Agents
D007546:Isoquinolines; D003473:Neuromuscular Nondepolarizing Agents; D000077590:Mivacurium