Comparison between the Datex-Ohmeda M-NMT® module and a force-displacement transducer for monitoring neuromuscular blockade

Background and objective: The Datex-Ohmeda neuromuscular transmission module (M-NMT)(R) is a new monitor that is part of the AS/3(R) anaesthesia monitor. It incorporates a mechanosensor, which is a piezoelectric polymer attached to the hand. The module was compared with a force transducer in 30 patients requiring neuromuscular blockade. Methods: Anaesthesia was induced with fentanyl and propofol, and tracheal intubation was performed without muscle relaxants. Neuromuscular blockade was assessed by the test module on one arm and the force transducer on the other arm. When the response to train-of-four stimulation had been stable in both arms for 3 min, rocuronium 0.2 mg kg(-1) was injected intravenously. During recovery from blockade, the train-of-four ratio was measured in 15 patients, and the ratio of response to double-burst stimulation in the other 15 patients. Data analysis was by difference plots. Results: Both devices had acceptable coefficients of repeatability. The M-NMT(R) module was biased by +1.3% (upper limit of agreement 14.2%, lower limit - 12.9%) for the recovery of the train-of-four ratio, and by + 1.09% (17%, - 16%) for the recovery of double-burst stimulation ratio. Conclusions: The Datex-Ohmeda M-NMT(R) gives measurements that are repeatable and gives good enough correspondence with a force transducer that it can be used clinically to assess recovery of neuromuscular blockade, but the limits of agreement rule out research applications.