The incidence of postoperative residual curarization following the use of intermediate-acting muscle relaxants and related factors.

Purpose: To evaluate the incidence of residual curarization (RC) and related risk factors in the early and late postoperative periods in patients receiving general anesthesia with intermediate-acting muscle relaxants.

Methods: Two-hundred and eight American Society of Anesthesiologists class I and II patients, aged 18-70 years, who underwent general anesthesia with intermediate-acting muscle relaxants, were included. Heart rate, blood pressure, oxygen saturation, tympanic temperature were recorded for each patient who was transported to the recovery room, every 10 minutes by a trained nurse. To define the efficacy of residual muscle relaxants, neuromuscular monitoring was performed, and Train of Four (TOF) ratios < 90% were regarded as RC whereas ratios ≥ 90% were considered as adequate neuromuscular recovery in early and late recovery periods. Age, duration of anesthesia, repeated doses, reversal and types of intermediate-acting neuromuscular blockers were evaluated as risk factors for RC. Logistic Regression Analysis was performed to define the risk factors for RC in early and late periods.

Results: The RC rate was 10.6% in the early recovery period, and short duration of anesthesia, repeated doses and lack of reversal use were the risk factors for RC. However, RC rate was 2.9% in the late recovery period, and the only risk factor was repeated doses.

Conclusion: Reversal use was shown to reduce residual effects of intermediate-acting muscle relaxants in early recovery period, whereas risk of RC in 30 min in PACU was shown to increase with repeated doses of muscle relaxants.