Letters to the Editor: Letters & Announcements
To the Editor:
Assessing residual neuromuscular blockade using acceleromyography in postoperative awake patients can be deceptive because of the poor reproducibility of the train-of-four measurements (1). We think that neuromuscular blockade monitoring should not be performed in awake patients but rather should be performed before tracheal extubation. Moreover, the resulting measurements are probably less variable, making their interpretation easier.
To this aim, we investigated after Ethical Committee approval the train-of-four ratio variability in 20 patients under general anesthesia (propofol, sufentanil, rocuronium, and sevoflurane). At the end of surgery, two electrodes were placed over the ulnar nerve at the wrist. The four fingers were fixed with tape on the armboard. We used the TOF-Watch SX (Organon, Oss, The Netherlands) to stimulate the ulnar nerve (2 Hz 0.2 ms TOF, 50 mA intensity) and to record the evoked thumb responses twice at 15-s intervals (train-of-four ratio ranging from 0.6 to 1).
The evaluation of repeatability between each paired train-of-four ratio determinations was performed by assessing the bias, the precision, and the limits of agreement using the Bland and Altman method (2).
Our results show much less variability of acceleromyography measurements than Baillard et al. (Table 1). We conclude that acceleromyography should be performed before emergence from anesthesia to more easily ensure complete neuromuscular recovery.
Philippe E. Dubois
Maximilien J. Gourdin
Department of Anesthesiology
Department of Biostatistics
University of Louvain
University Hospital of Mont-Godinne
1. Baillard C, Bourdiau S, Le Tourmelin P, et al. Assessing residual neuromuscular blockade using acceleromyography can be deceptive in postoperative awake patients. Anesth Analg 2004;98:854–7.
2. Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986;8476:307–10.