Postoperative residual curarization: clinical observation in the post-anesthesia care unit

Neuromuscular blocking agents (NMBAs) are widely used during the induction and maintenance of anesthesia. Postoperative residual curarization (PORC) following the use of NMBAs still occurs even though intermediate-acting NMBAs were used. Train-of-four (TOF) stimulation is used to quantify the degree of neuromuscular blockade. The TOF ratio of 0.7 in the adductor pollicis muscle was associated with normal respiratory function. Pharyngeal function returned to normal while the TOF ratio reached 0.9. The aim of this study was to survey the PORC in the post-anesthesia care unit (PACU).

In this observational study, 308 patients who received general anesthesia with NMBAs were enrolled. Residual curarization was evaluated using the TOF-Watch acceleromyograph upon arrival in the PACU. Three consecutive TOF stimulations were applied and recorded at 15-second intervals. Two thresholds of TOF ratios (0.9 and 0.7) were used to assess the presence of residual curarization.

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 male and female patients were significant (p = 0.014). In terms of weight, the differences between the patients with ratios > 0.9 and < or = 0.9 were significant (p = 0.013). There were 67, 49, 15, and three patients who received reversal medication in the > 0.9 group, < or = 0.9 and > 0.7 group, and < or = 0.7 group, respectively. The differences of the TOF ratios between the patients who received and those who did not receive reversal medication were not significant (p = 0.91).

PORC is still a clinical problem in the modern PACU. Objective neuromuscular monitoring needs to be performed to ensure patient safety.