Assessment of Neuromuscular Transmission by the Evoked Acceleration Response. An Evaluation of the Accuracy of the Acceleration Transducer in Comparison with a Force Displacement Transducer

This paper presents preliminary observations on an acceleration-responsive transducer designed to monitor neuromuscular transmission. Simultaneously evoked acceleration and tension responses of the adductor pollicis muscles were studied. Registrations were obtained during recovery from atracurium-induced block in 29 individuals in neurolept II anaesthesia (Group I) and in 4 ICU patients (Group II) sedated with pentobarbital or midazolam. Regression analysis of 1567 train-of-four (TOF) registrations, in regard to TOF-ratio (T4/T1) and first twitch ratio (T1/T0), demonstrated regression coefficients (b) and correlation coefficients (r) in the range 0.91-1.06 and 0.89-0.98, respectively. During 1 Hz single twitch stimulation and post-tetanic count stimulation, b and r were in the range 0.85-1.03 and 0.77-0.90, respectively. Following administration of edrophonium (n = 6, Group I) a deviation of T1/T0 regression values was observed in four individuals, i.e. 0.48 (b) and 0.56 (r). This investigation proved a good level of accuracy of the acceleration transducer compared to the force displacement transducer during spontaneous and neostigmine-induced recovery from atracurium block. The acceleration transducer-based system does not require a rigid suspension and seems to have a good monitoring potential in clinical assessment of neuromuscular transmission.