Comparison of the TOFscan Simultaneous Measures at the Thumb and the First Toe During Recovery of Neuromuscular Function Following Rocuronium Administration

The development of advanced competence in laparoscopic surgery, robotic surgery and the broadening of indications for partial or total laparoscopy techniques created a novel environment where patients need to be deeply paralyzed and positioned in form fitting mattresses to ensure high quality exposure and security in extreme positioning. It is now undisputed that clinical evaluation done any other way than by a objective neuromuscular function monitor may produce faulty conclusions. The elements of the operating setup force anesthesiologists to adapt the way they monitor muscle relaxation since the hands are generally not available for neuromuscular function monitoring. In order to measure properly the level of residual paralysis, the thumb must be able to move freely in a device creating a light preloading on the adductor pollicis allowing to evaluate the force generated during standardized stimulation through accelerometry, the TOFscan device. The corrugator supercilli and orbicularis oculi muscles, an alternate positioning for the accelerometer is sometimes the fallback spot for monitoring. The problem with that muscle is that it does not have the same time curve sensitivity to muscle relaxant than the perilaryngeal muscle have. The investigators are looking for a good representation of the level of patency of the perilaryngeal muscle to ensure that the patient will be able to breath normally after extubation, they must turn to another target. Previous observations have suggested that the monitoring of the hallux flexor muscle could represent a valid alternative. The confirmation of this hypothesis would allow for easy, reproducible, evaluation of the level of muscle relaxation at the perilaryngeal muscles, helping to procure safer conditions for tracheal extubation. Neuromuscular blocking agents (NMBAs) are administered by anesthesiologists during general anesthesia to facilitate endotracheal intubation and/or surgical conditions. Postoperative residual neuromuscular blockade (rNMB), is an adverse event frequently observed after extubation in the postanesthesia care unit (PACU) after surgery. rNMB is associated with upper airway obstruction, reduced pharyngeal muscle coordination, decreased functional residual capacity, and impaired hypoxic ventilatory response and may lead to critical cardiopulmonary complications. To prevent those complications, monitoring NMBAs activity and timely and adequate dosage of reversal agents necessitate precise and valid monitoring.

The current literature supports the exclusive use of quantitative measurements of residual paralysis, subjective monitoring caries to much error in evaluating the level of blockade and is responsible for PACU residual paralysis and its complications. It is well accepted that no amount of rNMB is acceptable (TOF < 1) around extubation periods, a necessary step to ensure safety that relies on timely and correct dosage of the reversal agents.

When TOFscan measures are done on partially mobile thumbs, or transducers positioned in non-optimal fashion, the measure observed (deep blockade) will either delay the reversal procedure because of presumed very deep level paralysis or suggest high doses of reversal agents at a significant cost.

The investigators are confident that validating the measures done at the hallux flexor will allow for easy, relevant and valid estimation of residual paralysis and create a safer environment for muscle relaxation reversal and extubation.