Comparison of the Performances of the Train-of-Four Ratio and the Modified Train-of-Four Ratio During Reversal of Deep Neuromuscular Blockade With Sugammadex

Neuromuscular blockers (NMB) agents are commonly used drugs in anesthesia for facilitating airway management, improving surgical conditions, and inducing immobility in critical situations. As a natural consequence of their use, postoperative residual neuromuscular block has been associated with serious postoperative complications such as upper airway obstruction, reintubation, atelectasis, pneumonia, prolonged stay in the post-anesthesia care unit (PACU), and decreased patient satisfaction. The incidence of residual block at the end of surgery and/or in the PACU is approximately 64% according to the literature .

Various factors contribute to the high incidence of residual neuromuscular block, including variability in the duration of action of neuromuscular blocker agents, variability in the time it takes for antagonist drugs to restore neuromuscular function, and clinicians' reliance on unreliable methods for assessing neuromuscular strength, such as continuous head lifting, grip strength, or respiratory measurements (e.g., tidal volume, inspiratory force), and the subjective evaluation of peripheral nerve stimulation responses . Residual neuromuscular block is a significant patient safety concern, and its detection and risk reduction are crucial for improving patient outcomes. One of the objective methods for assessing neuromuscular function is the Train of Four (TOF), which is an acceleromyographic peripheral nerve stimulator.

The effectiveness of TOF as an objective and quantitative assessment of neuromuscular block and its role in reducing postoperative complications has been demonstrated in numerous studies. In 2023, the "American Society of Anesthesiologists Practice Guidelines for Monitoring and Antagonism of Neuromuscular Blockade" presented it with a moderate level of evidence and a high recommendation level. Likewise, in 2023, the European Society of Anesthesiology and Intensive Care's "Perioperative Management of Neuromuscular Blockade" guideline recommended TOF monitoring as part of routine perioperative monitoring with a 1B level of evidence .

TOF involves delivering four brief electrical impulses to a peripheral nerve at a frequency of 2 Hz and evaluating the resulting "twitches." The ratio of the response to the fourth stimulus to the response to the first stimulus (T4/T1) is referred to as the TOF ratio. Acceptable recovery of neuromuscular function is defined as a TOF ratio greater than or equal to 0.9. In a prospective study conducted in 2022 by Schmartz and colleagues, they compared a modified TOF ratio (T4/Tr) to the classic TOF ratio (T4/T1) against a reference measurement and demonstrated that the T4/Tr ratio is a better indicator of readiness for adequate recovery and safe extubation from non-depolarizing neuromuscular blockade compared to the classic TOF ratio (T4/T1) . This result suggests that the classic TOF ratio may overestimate the degree of true neuromuscular recovery, potentially leading to early tracheal extubation, increased risk of postoperative pulmonary complications, and endangering patient safety.

The aim of our study is to determine whether the differences in mTOF/classic TOF durations, as shown by Schmartz and colleagues in spontaneous neuromuscular recovery, also result in significant differences when rocuronium is reversed with sugammadex.