Comparison of train-of-four ratios measured with Datex-Ohmeda's M-NMT MechanoSensor™ and M-NMT ElectroSensor™.

Neuromuscular blockade is usually monitored using train-of-four (TOF) stimulation pattern. A TOF ratio of higher than 90 % is recommended to reduce the risk of adverse effects after anaesthesia. TOF ratio 90 % is used in clinical practice with all different neuromuscular monitors. Kinemyography (KMG) is one commercialized method to obtain numerical TOF values. We compared the KMG data obtained with Datex M-NMT MechanoSensor™ module, to the EMG data collected with Datex ElectroSensor™, during clinical anaesthesia. Ipsilateral comparisons of the sensors were performed in 20 female patients during clinical procedures in propofol-remifentanil anaesthesia. After initial bolus dose of rocuronium (0.6 mg/kg), the spontaneous recovery of TOF ratio and T1 % were monitored. KMG gave higher TOF values than EMG. The difference was significant at KMG TOF values of 40 % or higher. After anaesthetic induction, but before administration of rocuronium, both TOF sensor values drifted from the TOF value of 1.0, showing either significant spontaneous fade (T1 > T4) or tendency of reverse fade (T1 < T4). KMG overestimates the recovery from neuromuscular blockade when compared with EMG. KMG and EMG cannot be used interchangeably, and TOF ratio 90 % cannot be considered as adequate level of recovery with all monitoring devices.