Purpose: A train-of-four ratio (TOF ratio) of >0.9 should be the clinical cut-off to avoid residual paralysis. However, it is not rare to extubate patients without measurement of the TOF ratio, although the safe interval from the last administration of rocuronium assuring a TOF ratio of >0.9 has not been established in the daily clinical setting. In this study, to estimate the safe interval to avoid residual paralysis, we retrospectively selected patients in whom the TOF ratio was measured during remifentanil administration before extubation, and we studied the characteristics of recovery from the neuromuscular blockade produced by the empirical use of rocuronium.
Methods: Patients undergoing surgery under general anesthesia with sevoflurane and remifentanil were studied (n = 134). Rocuronium was administered at 0.7-1.0 mg/kg for tracheal intubation, and repeated bolus administration (10 mg) or continuous infusion (15-25 mg/h) was performed by the anesthesiologists in charge of the patient to maintain intraoperative paralysis. At the end of the surgery, the TOF ratio was measured, during remifentanil infusion and the contribution of clinical parameters to spontaneous recovery from the rocuronium-induced paralysis was studied by multivariate logistic regression analyses.
Results: Spontaneous recovery from rocuronium-induced paralysis within 2 h after the last administration of rocuronium varied among the patients. Multivariate logistic regression analyses showed that age (P = 0.002) and time elapsed from the last administration of rocuronium (P < 0.0001) significantly contributed to TOF recovery, and elderly patients demonstrated significantly slower recovery.
Conclusion: Because of the large variation in the recovery from rocuronium-induced paralysis, TOF-based evaluation of residual paralysis is essential to determine the appropriate indication for reversal, especially for elderly patients.