• T Suzuki, N Fukano, O Kitajima, S Saeki, and S Ogawa.
• Department of Anesthesiology, Surugadai Nihon University Hospital, 1-8-13, Kanda-Surugadai, Chiyoda-Ku, Tokyo 101-8309, Japan. suzukit@cd5.so-net.ne.jp
• Br J Anaesth. 2006 Jan 1;96(1):44-7.

BackgroundThis study was designed to recognize the importance of normalizing postoperative acceleromyographic train-of-four (TOF) ratio by the baseline TOF value obtained before neuromuscular block for ensuring adequate recovery of neuromuscular function.MethodsIn 120 patients, TOF responses of the adductor pollicis to the ulnar nerve stimulation were monitored by acceleromyography (AMG) during anaesthesia using propofol, fentanyl and nitrous oxide. Control TOF stimuli were administered for 30 min. A TOF ratio measured at the end of control stimulation was regarded as a baseline value. Neuromuscular block was induced with vecuronium 0.1 mg kg(-1) and was allowed to recover spontaneously. Duration to a TOF ratio of 0.9 as calculated by AMG (DUR-raw 0.9) was compared with that of 0.9 as corrected by the baseline TOF ratio (i.e. 0.9 x baseline TOF ratio; DUR-real 0.9).ResultsBaseline TOF ratios ranged from 0.95 to 1.47. The average TOF ratios observed every 5 min were constant throughout control stimulation from at time zero mean (SD) [range]; 1.11 (0.09) [0.94-1.42] to at 30 min 1.13 (0.11) [0.95-1.47]. The DUR-real 0.9 was 91.0 (18.0) [51.3-131.0] min and was significantly longer than the DUR-raw 0.9 (81.2 (16.3) [41.3-123.0] min).ConclusionsBaseline TOF ratios measured by AMG are usually more than 1.0 and vary widely among patients. Therefore a TOF ratio of 0.9 displayed postoperatively on AMG does not always represent adequate recovery of neuromuscular function and should be normalized by baseline value to reliably detect residual paralysis.

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