Train-of-four ratio recovery often precedes twitch recovery when neuromuscular block is reversed by sugammadex

Background: Sugammadex reverses rocuronium-induced neuromuscular block (NMB). In all published studies investigating sugammadex, the primary outcome parameter was a train-of-four (TOF) ratio of 0.9. The recovery time of T1 was not described. This retrospective investigation describes the recovery of T1 vs. TOF ratio after the reversal of NMB with sugammadex. Methods: Two studies were analyzed. In study A, a phase II dose-finding study, ASA I-II patients received an intravenous (IV) dose of rocuronium 1.2 mg/kg, followed by an IV dose of sugammadex (2.0, 4.0, 8.0, 12.0 or 16.0 mg/kg) or placebo (0.9% saline) after 5 min. In study B, a phase III trial comparing patients with renal failure and healthy controls, rocuronium 0.6 mg/kg was used to induce NMB; sugammadex 2.0 mg/kg was administered at reappearance of T2. Neuromuscular monitoring was performed by acceleromyography and TOF nerve stimulation. The primary efficacy variable was time from the administration of sugammadex to recovery of the TOF ratio to 0.9. Retrospectively, the time to recovery of T1 to 90% was calculated. Results: After the reversal of rocuronium-induced NMB with an optimal dose of sugammadex [16 mg/kg (A) or 2 mg/kg (B)], the TOF ratio recovered to 0.9 significantly faster than T1 recovered to 90%. Clinical signs of residual paralysis were not observed. Conclusion: After the reversal of NMB by sugammadex, full recovery of the TOF ratio is possible when T1 is still depressed. The TOF ratio as the only measurement for the adequate reversal of NMB by sugammadex may not always be reliable. Further investigations for clinical implications are needed.