Background and Goal of Study: Acceleromyography (AMG) is used in clinical practice to monitor neuromuscular blockade. However, problems remain in obtaining stable values, making the interpretation of results difficult (1). Furthermore, the thumb must move freely which is frequently impossible under the sheets during the surgical procedure.
This study compares train-of-four ratios (TOFr) recorded at the end of surgery with mechanomyography (MMG), electromyography (EMG) and AMG protected inside the TOF-tube, a rigid tubular device allowing safe positioning of the hand while ensuring thumb mobility under the surgical sheets (2).
Materials and Methods: After Ethical Committee approval, neuromuscular blockade was investigated in 20 informed patients under general anaesthesia. Two consecutive TOFr (15s interval) were obtained on both hands simultaneously using on one side MMG and EMG, and on the other AMG installed inside the TOF-tube. The evaluation of repeatability between each paired TOFr was performed by assessing the bias, the precision, and the limits of agreement using the Bland and Altman method.
Results: Expressed in % as mean ± SD
Mean TOFr was 75 ± 15 at the end of surgery.
Conclusion: Inside the TOF-tube, its protective device, AMG shows an inter-measurement variability of the same magnitude as EMG. This allows a better interpretation of AMG results during the surgical procedure.
1 Baillard et al. Assessing residual neuromuscular blockade using acceleromyography can be deceptive in postoperative awake patients. AnesthAnalg 2004;98:854-7.
2 Dubois P.E. et al. TOF-tube: a new protection for NMB monitoring. EJA 2001;18 Suppl 21:A89.