An acceleromyographic train-of-four ratio of 1.0 reliably excludes respiratory muscle weakness after major abdominal surgery : a randomized double-blind study

Purpose: This randomized double-blind study was designed to determine if respiratory muscle weakness - measured by maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP), forced vital capacity (FVC), and forced expiratory volume in one second (FEV1) - persists even if an acceleromyographic train-of-four ratio (TOFR) of 1.0 is reached after major abdominal surgery. Methods: Twenty patients underwent respiratory function tests before induction of anesthesia. Rocuronium was given, and the tests were repeated after extubation when the TOFR reached 1.0. The patients were then randomized to receive sugammadex 1 mg·kg-1 or placebo, and the same tests were repeated five and 20 min later. Between-group comparisons were carried out with a mixed-model analysis of variance analysis. Results: After anesthesia and adequate epidural analgesia, MIP and MEP decreased by 60% in both groups. In the placebo group, MIP decreased from a pre-induction value (median [range]) of 61.8 [31.3-96.1] to 19.6 [8.3-58.3] cm H2O after extubation without significant variation five and 20 min after placebo. In the sugammadex group, MIP decreased from a pre-induction value of 57.8 [13.0-96.4] to 20.5 [6.4-67.3] cm H2O after extubation. No differences were recorded after sugammadex administration (P = 0.246 between groups). In the placebo group, MEP decreased from 88.8 [65.1-120.3] before induction to 37.6 [13.4-70.6] cm H2O after extubation. In the sugammadex group, MEP decreased from 85.5 [58.6-132.7] to 30.8 [10.5-60.5] cm H2O, with no improvement five and 20 min after either placebo or sugammadex administration (P = 0.648). Similarly, the FCV and FEV1 decreased 30-40% after extubation in both study groups. Conclusion: Acceleromyographic TOFR of 1.0 excludes residual neuromuscular paralysis. However, major respiratory dysfunction is observed after abdominal surgery. This trial was registered at ClinicalTrials.gov: NCT01503840.