Monitoring of neuromuscular block for safe anesthesia: FAQs for proper understanding

In August 2025, the Japanese Society of Anesthesiologists revised the section on neuromuscular block monitoring in its guidelines "Monitoring for Safe Anesthesia". The revised section states: "When using neuromuscular blocking agents and antagonists, it is recommended to quantitatively evaluate the depth of neuromuscular block and confirm a TOF ratio of ≥ 0.9 at the hand before tracheal extubation," replacing the previously revised 2019 statement, which simply recommended "Monitor the depth of neuromuscular block when using neuromuscular blocking agents and antagonists." The latest revision explicitly states the use of quantitative neuromuscular monitoring and recommends objectively determining a TOF ratio of ≥ 0.9 for adequate recovery. Currently, rocuronium is the primary neuromuscular blocking agent used in Japan. However, its duration of action is influenced by factors such as age, sex, patient condition, and type of anesthetic agent and, therefore, shows significant individual variation. Therefore, neuromuscular monitoring is essential for maintaining an appropriate depth of neuromuscular block and avoiding rocuronium overdose. Quantitative monitoring of the TOF ratio is particularly essential during emergence from anesthesia, as it also serves as an indicator for calculating the optimal dose of the rocuronium antagonist sugammadex. Failure to administer the optimal dose of sugammadex carries risks of residual neuromuscular blockade and recurarization, potentially leading to critical respiratory complications postoperatively, such as hypoxia, atelectasis, or pneumonia. Evaluation of the TOF ratio in hand muscles indicates recovery of the upper airway muscles, which are highly sensitive to rocuronium. This would facilitate safe tracheal extubation and ensure adequate ventilatory recovery.