Simultaneous determination of neuromuscular block at the larynx, diaphragm, adductor pollicis, orbicularis oculi and corrugator supercilii muscles.

We simultaneously determined the neuromuscular blocking effect of mivacurium 0.2 mg kg(-1) at five muscles in 20 women undergoing gynaecological surgery. Evoked electromyographic responses were obtained using surface electromyography (EMG) at the adducting laryngeal muscles, the diaphragm (lateral to vertebrae T12/L1 or L1/L2) and the adductor pollicis muscle and acceleromyographic (AMG) responses were measured at the orbicularis oculi and the corrugator supercilii muscle. Onset time and times for the first twitch response (T1/T0) to return to 25, 75 and 90% at the adducting laryngeal muscles and the diaphragm were significantly (P<0.005) shorter than at the adductor pollicis, the corrugator supercilii or the orbicularis oculi muscles (mean (SD) onset time: 89 (26) s and 78 (17) s to 202 (45) s, 152 (41) s, 194 (40) s; T1/T0=25%: 10.4 (1.5) and 11.4 (1.2) min versus 20.5 (3.9), 15.9 (3.3), 16.3 (3.7) min; T1/T0=90%: 15.5 (1.6) and 16.1 (1.6) min versus 27.4 (4.6), 21.5 (3.8), 23.3 (5.1) min). Onsetand clinical duration of neuromuscular block at the larynx and the diaphragm after mivacurium 0.2 mg kg(-1) are shorter than in the peripheral muscles. Monitoring of neuromuscular block in the diaphragm was successfully used in all patients.