Monitoring the Depth of Neuromuscular Blockade

Purpose of Review: In 2023, the American Society of Anesthesiologists published its first practice guideline document regarding the monitoring and antagonism of neuromuscular blockade. Those guidelines specifically recommend the use of QUANTITATIVE neuromuscular blockade monitoring — and recommend AGAINST relying on clinical assessments or dependence on the use of peripheral nerve stimulator (PNS — qualitative monitoring). This article reviews the data behind those recommendations. Recent Findings: We describe the general failure of most clinical assessments (e.g., head lift, grip strength) to verify full reversal [as defined as a train-of-four (TOF) ratio of > 0.9 using quantitative methods] as well as the insensitivity of information obtained by the use of a PNS, such as the visual assessment of the TOF, tetanus, or double-burst stimulation (DBS) — although we recognize that a PNS can be used to titrate intraoperative dosing of neuromuscular blocking drugs and under very limited conditions can allow successful reversal with either neostigmine or sugammadex. Finally, we review quantitative technology and pros and cons of different methods (acceleromyography, electromyography, kinemyography) and attempt to provide evidence that even with the use of sugammadex, it is impossible to reliably ensure complete reversal without such quantitative monitoring. Summary: Careful — and ideally quantitative — neuromuscular blockade monitoring is the only known method for ensuring complete reversal after any surgical procedure involving non-depolarizing relaxants.