Comparison of measurements obtained with TOF-Cuff placed on the arm and the TOF-Scan on the adductor pollicis muscle during general anaesthesia using mivacurium: a prospective observational clinical trial

Adequate neuromuscular monitoring of patients is essential to verify complete recovery of neuromuscular function before tracheal extubation. This study aimed to assess the correlation between the values acquired from the brachialis muscle using TOF-Cuff and those obtained from the adductor pollicis muscle with TOF-Scan during anaesthesia with mivacurium. Twenty-five patients were enrolled in the observational clinical trial, with the TOF-Cuff positioned on the upper arm and the TOF-Scan on the thumb. Train-of-four (TOF) values were simultaneously recorded by both devices at 30-second intervals before intubation. Subsequently, measurements were taken every 5 min until the removal of the endotracheal tube. Bland-Altman analyses were conducted to compare assessed endpoints obtained by using the TOF-Cuff and the TOF-Scan. The median onset time measured with TOF-Cuff was numerically longer compared to the TOF-Scan score (120 s vs. 90 s, P = 0.42). Spearman rank correlation revealed a significant positive correlation between onset times measured by TOF-Cuff and TOF-Scan (R = 0.73, P = 0.0001, 95% CI 0.446 to 0.875). For the time to recovery assessed with both methods, Spearman correlation coefficient was R = 0.35 and did not reach statistical significance (P = 0.1). Multiplying the time to recovery from the last dose (according to TOF-Scan) by 0.43 to 2.66, provided concordance with the TOF-Cuff result for the entire range of study group. Conclusion. The concordance between the TOF-Scan on the adductor pollicis and the TOF-Cuff on the upper limb was found to be good. However, both devices showed a false-negative result in patients with clinical symptoms of preterm recovery.