Monitoring recovery from rocuronium-induced neuromuscular block using acceleromyography at the trapezius versus the adductor pollicis muscle: an observational trial

Abstract

We conclude that recording evoked acceleromyographic responses at the trapezius muscle is an acceptable alternative when monitoring from the adductor pollicis muscle is compromised. Nevertheless, we caution that recording a 90% TOF response at the trapezius muscle may overestimate functional recovery from the neuromuscular blockade. This trial was registered at ClinicalTrials.gov identifier, NCT01849198.

Monitoring recovery from neuromuscular block using acceleromyography at the trapezius muscle: problems that must be considered

“…Therefore, following ten minutes of train-of-four (TOF) stimulation, the AMG was recalibrated and ten T1 and TOF ratio values were recorded and served as controls. 1 In my opinion, this is a sign of insufficient signal stabilization. One explanation could be that the staircase phenomenon (frequency-dependent twitch potentiation) caused the signal drift of the control T1.…”

“…These varying staircase characteristics could be part of the reason why eight subjects were excluded because of signal drift. 1 Thus, the results of Soltesz et al would be more valid if they had used the recommended 50-Hz tetanic preconditioning before calibration to increase signal stability. 2,4 Nevertheless, the TOF ratio is not influenced by the staircase effect and may be more dependent on an elastic preload (Figure).…”

“…The authors concede that AMG at the trapezius muscle may overestimate neuromuscular recovery, but there are some other issues that also deserve further discussion. 1 The observational, sex-specific study design, with missing randomization of the stimulation sites, may limit the validity of the study. Furthermore, these investigators immobilised the stimulation arm, leaving the thumb free to move.…”

“…Furthermore, these investigators immobilised the stimulation arm, leaving the thumb free to move. 1 There is good evidence, however, that applying an elastic preload to the thumb (Hand AdapterÒ; Organon Ltd., Dublin, Ireland), decreases signal variability and can increase the precision of the onset and time course of the neuromuscular block. 2,3 In their study, calibration of the TOF-Watch SX (Essex Pharma GmbH, Munich, Germany) was performed using the Cal-2-mode with a stimulus impulse width of 0.1 msec -in contrast to the recommended standard width of 0.2 msec.…”

“…One explanation could be that the staircase phenomenon (frequency-dependent twitch potentiation) caused the signal drift of the control T1. 1,4 Because all T1 values are related to the control T1, low variability of this baseline is important for data precision. 2 A staircase effect rapidly increases T1 during TOF stimulation at the adductor pollicis muscle to 148% ± 19% of the baseline T1 after 15 min and then more slowly to 158% ± 26% after 25 min.…”