Performance of acceleromyography with a short and light TOF-tube compared with mechanomyography

Abstract

Disturbances in the thumb's movement interfere with the functioning of acceleromyography in many clinical settings. The short and light (SL) train-of-four (TOF)-Tube is a new version of a rigid tubular device that was designed to protect the thumb from external disturbances during surgery, even when the hand is not accessible by the anaesthesiologist. To compare the precision and performance of acceleromyography performed with the aid of the SL TOF-Tube (AMGTT) with standard isometric mechanomyography (MMG). Simultaneous arm-to-arm comparison of both methods in the same anaesthetised patient. A monocentric study, performed from September 2007 to June 2008. Nineteen ASA I to II patients scheduled to undergo lower limb orthopaedic surgery under general anaesthesia. Neuromuscular transmission monitoring during baseline, onset and spontaneous recovery of rocuronium-induced neuromuscular block. Initial baseline and repeatability coefficients were assessed during 10 consecutive measurements of the first twitch height (T1) and TOF T4/T1 ratio and compared using a z test. The spontaneous recoveries of defined blockade levels (onset, T1 25% of initial calibration and TOF ratio 0.9) were compared in terms of duration and intensity. Agreement between both techniques was assessed by the Bland-Altman method. The mean ± SD control TOF ratios were 98 ± 1% (MMG) and 103 ± 2% (AMGTT). The repeatability coefficients were higher (P < 0.001) and the onset was longer (mean 0.44 min) (P < 0.001) when they were measured by AMGTT. The recoveries of T1 25% and TOF ratio 0.9 were not significantly different between the two methods, and the limits of agreement were in the usual range of contralateral comparisons (-19 and +24% for TOF ratio 0.9). Compared with mechanomyography, acceleromyography performed with the aid of an SL TOF-Tube offered acceptable precision and equivalent performance during neuromuscular block recovery.