Assessment of spontaneous neuromuscular recovery: A comparison of the TOF-Cuff^® with the TOF Watch SX^®

Background: TOF-Cuff^® is a modified blood pressure cuff used to monitor neuromuscular block. We compared the assessment of spontaneous neuromuscular recovery between TOF-Cuff^® (test device) and TOF Watch SX^® (reference device).

Methods: Forty patients aged 18-65 years undergoing elective surgery were enrolled. TOF-Cuff^® was installed on an upper arm and the TOF Watch SX^® on the thumb of the opposite side. Anaesthesia was induced and maintained with intravenous propofol and sufentanil. After induction, the devices were calibrated and continuous train-of-four (TOF) stimulation was started. A single intravenous dose of rocuronium (0.6 mg kg^-1 ) was administered for intubation. The primary outcome was total recovery time (time in minutes from the injection of rocuronium to a normalized TOF ratio of 90%). Agreement between the two devices was calculated using mean difference and limits of agreement.

Results: The primary outcome could be analysed in 27 patients because of 13 exclusions due to neuromuscular block reversal for shorter procedure surgical time, necessity of reinjection of rocuronium or technical failures of one of the two devices. Median total recovery time with the test device was 45 minutes (interquartile range [IQR] 38.5-61.5) and 63 minutes (IQR 51.1-74.5) with the reference device. Total recovery time with the test device was on average 16.4 minutes shorter (limits of agreement, -6.1 to 39); increasing total recovery time was associated with increasing difference. The TOF ratio of the reference device was on average 0.59 (SD 0.23) when the test device indicated complete recovery. The TOF ratio of the test device was on average 0.98 (SD 0.03) when the reference device indicated complete recovery.

Conclusion: When compared with the TOF Watch SX^® , TOF-Cuff^® overestimates spontaneous recovery of a rocuronium-induced neuromuscular block.