Mindray 3-directional NMT Module (a new generation “Tri-axial” neuromuscular monitor) versus the Relaxometer mechanomyograph and versus the TOF-Watch SX acceleromyograph

Recently introduced Mindray “3-directional” neuromuscular transmission transducer (NMT, Shenzhen, China) acceleromyograph) claim to monitor thumb movement in 3 different directions. We compared NMT with the gold standard Relaxometer® mechanomyograph (MMG, Groningen University, Netherlands) in Study-1 and with TOF-Watch SX™ (WTCH) acceleromyograph from which it was developed in Study-2. We used first twitch (T1%) and train-of-four (TOF) ratio rocuronium 0.6 mg kg−1 neuromuscular block to evaluate NMT diagnostic accuracy in indicating 3 clinically relevant time points namely; MMG T1 5% (95% twitch depression) for tracheal intubation, MMG T1 25% for repeat neuromuscular blocking agents (NMBAs) administration, and MMG 0.9 TOF ratio full neuromuscular block recovery. We compared onset time (time from beginning of rocuronium administration until maximal depression), Dur25 (time until T1 25% recovery) and Dur0.9 (time until 0.9 TOF ratio recovery). In Study-1, NMT showed low sensitivity in indicating MMG time for tracheal intubation, repeat NMBAs administration and full neuromuscular block recovery (6.25%, 38.9% and 38.9% respectively). NMT onset time, Dur25 and Dur0.9 (2:51 ± 00:57, 36:50 ± 24:25, 70:08 ± 25:27 min:s) were significantly longer than MMG (1:56 ± 00:46, 30:26 ± 20:24, 62:03 ± 20:01). In Study-2, NMT onset time, Dur25 and Dur0.9 (02:37 ± 00:53, 35:38 ± 11:54, 53:40 ± 13:49) were not significantly different than WTCH (02:23 ± 00:45, 33:27 ± 12:51, 53:57 ± 12:47). NMT could not efficaciously detect MMG time for tracheal intubation; NMBAs repeat dose administration or full neuromuscular block recovery. Data from NMT cannot be used interchangeably with MMG. Our study revealed that NMT Tri-axial acceleromyography seems to offer no advantage over the MMG gold standard or the classic Mono-axial TOF-Watch SX monitor.