An acceleromyographic train-of-four (TOF) ratio of 0.90 at extubation does not prevent postoperative pulmonary complications in surgical patients receiving non-depolarising muscle relaxants. This recent observation suggests that a more selective neuromuscular transmission monitoring parameter is mandatory to detect more precisely any remaining residual paralysis. The aim of our proof-of-concept study was to evaluate, in patients receiving rocuronium, the degree of 100-Hz, 5-s tetanic fade present when the acceleromyographic TOF ratio has recovered to 0.90.

Twenty adult patients scheduled for surgery under general anaesthesia were included. Before anaesthesia induction, a TOF-Watch SX™ and a VISUAL-ITF© (a prototype monitor for recording isometric force) were positioned on both hands. After induction but before rocuronium injection, a 100-Hz, 5-s tetanus (TET0) was delivered to both ulnar nerves. Thereafter, TOF stimulations every 15 s were delivered to both arms until a TOF ratio > 0.90 was recorded; then, a 100-Hz, 5-s tetanus (TET1) was recorded on the VISUAL-ITF© monitor. The values of the tetanic parameters (force) recorded at TET0 and TET1 were compared using a Wilcoxon rank sum test.

Compared to TET0, tetanic parameters of TET1 were significantly lower (median [range]): maximal force 36.4 [19.2−82.6] vs. 25.5 [5.0−42.4] Newton (p <  0.005); residual force 36.2 [18.2−82.0] vs. 5.5 [0.20–38.3] Newton (p < 0.0001) and residual force/maximal force ratio 0.98 [0.89−0.99] vs. 0.17 [0.03−0.90] (p <  0.0001).

Our results confirm that even when the acceleromyographic TOF ratios have recovered to above 0.90, the contralateral 100-Hz, 5-s tetanic stimulus may show tetanic fade characteristic of residual neuromuscular block, and may help improve the safety of tracheal extubation.