Low-Dose Neostigmine at 0.7 Train-of-Four Ratio Safely Accelerates Neuromuscular Recovery: A Prospective Observational Study

Chang-Hoon Koo,1,2,* Chang Ik Choi,3,* Insun Park,1,2 Sohyun Lee,1 Ah-Young Oh1,2 1Department of Anesthesiology and Pain Medicine, Seoul National University Bundang Hospital, Seongnam, Korea; 2Department of Anesthesiology and Pain Medicine, Seoul National University College of Medicine, Seoul, Korea; 3Department of Anesthesiology and Pain Medicine, Anyang Sam Hospital, Anyang, Korea*These authors contributed equally to this workCorrespondence: Ah-Young Oh, Department of Anesthesiology and Pain Medicine, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, Korea, Tel +82-31-787-7506, Fax +82-31-787-4063, Email [email protected]: Neostigmine is recommended to reverse the minimal depth of the neuromuscular blockade. However, neostigmine administered at a minimal blockade may cause paradoxical muscle weakness. This study aimed to assess the efficacy and safety of neostigmine administered at a train-of-four (TOF) ratio of 0.7 for neuromuscular recovery.Patients and methods: This prospective observational study included 54 patients who underwent thyroid surgery under intravenous anesthesia. Neostigmine 20 mcg/kg was administered when the TOF ratio spontaneously recovered to 0.7 during surgery. The recovery times were recorded based on the time from a TOF ratio of 0.7 to 1.0 and 0.9. Outcomes were compared with those of patients with spontaneous recovery, including recovery times and incidence of adverse events, such as paradoxical muscle weakness.Results: Neostigmine administration significantly reduced recovery time from a TOF ratio of 0.7 to 1.0 (4.9 vs 10.2 min, P = 0.001), from 0.7 to 0.9 (3.3 vs 6.7 min, P = 0.002), and from 0.9 to 1.0 (1.5 vs 4.3 min, P = 0.003), compared with spontaneous recovery. Importantly, no patients exhibited a reduction in the TOF ratio after neostigmine administration, nor did they develop clinical signs or symptoms of paradoxical muscle weakness after surgery.Conclusion: Administering 20 mcg/kg neostigmine at a TOF ratio of 0.7 is effective and safe, facilitating neuromuscular recovery without adverse effects. This treatment regimen can enhance surgical workflow efficiency and reduce patient recovery times while maintaining patient safety.Keywords: neostigmine, neuromuscular blockade, neuromuscular recovery, train-of-four ratio, paradoxical muscle weakness