Postoperative Residual Curarization: Clinical Observation in the Post-anesthesia Care Unit

Background: Neuromuscular blocking agents (NMBAs) are widely used during the inductionand maintenance of anesthesia. Postoperative residual curarization(PORC) following the use of NMBAs still occurs even though intermediateactingNMBAs were used. Train-of-four (TOF) stimulation is used to quantifythe degree of neuromuscular blockade. The TOF ratio of 0.7 in the adductorpollicis muscle was associated with normal respiratory function.Pharyngeal function returned to normal while the TOF ratio reached 0.9. Theaim of this study was to survey the PORC in the post-anesthesia care unit(PACU).Methods: In this observational study, 308 patients who received general anesthesiawith NMBAs were enrolled. Residual curarization was evaluated using theTOF-Watch acceleromyograph upon arrival in the PACU. Three consecutiveTOF stimulations were applied and recorded at 15-second intervals. Twothresholds of TOF ratios (0.9 and 0.7) were used to assess the presence ofresidual curarization.Results: TOF ratios less than 0.7 and 0.9 were observed in 15 (5%), and 97 (31%)patients, respectively. The differences of the TOF ratios between the maleand female patients were significant (p = 0.014). In terms of weight, the differencesbetween the patients with ratios > 0.9 and ≦ 0.9 were significant (p= 0.013). There were 67, 49, 15, and three patients who received reversalmedication in the > 0.9 group, ≦ 0.9 and > 0.7 group, and ≦ 0.7 group,respectively. The differences of the TOF ratios between the patients whoreceived and those who did not receive reversal medication were not significant(p = 0.91).Conclusion: PORC is still a clinical problem in the modern PACU. Objective neuromuscularmonitoring needs to be performed to ensure patient safety.