Comparison of integrated evoked EMG between the hypothenar and facial muscle groups following atracurium and vecuronium administration

Abstract

In 17 healthy patients undergoing O2 · N2O · isoflurane anaesthesia, following atracurium or vecuronium administration, we compared simultaneous integrated evoked electromyograms (IEEMGS) during spontaneous recovery of the adductor digiti minimi (ADM) and orbicularis oris (OOM) muscle groups in response to train-of-four (TOF) stimulation of the ulnar and facial nerves, respectively. In all patients, the onset of neuromuscular recovery occurred first in the OOM. The time required to recover to a T4/T1 = 0.70 ± 0.01 (SD) was earlier in the OOM compared with the ADM muscles in both the atracurium (33.4 ± 5 vs46.5 ± 8,P< 0.005) and vecuronium (46.5 ± 12 vs 60.3 ± 20, P < 0.005) groups. When the OOM attained a T4/T1 = 0.70 ± 0.01, the simultaneous T4/T1 in the ADM was 0.29 ± 0.15 (P < 0.05) in the atracurium group and 0.41 ± 0.16 (P < 0.01) in the vecuronium group. We conclude that (1) the facial muscles (OOM) recover earlier than the hypothenar muscles (ADM) and (2) an EMG T4/T, = 0.70 in the facial muscles may not indicate adequate recovery of neuromuscular function. © 1991 Canadian Anesthesiologists.