Effects of different sugammadex doses on the train-of-four ratio recovery progression during rocuronium-induced neuromuscular blockade in the rat phrenic nerve hemidiaphragm

Background: In this study, we used an ex-vivo model to investigate the recovery pattern of both the train-of-four (TOF) ratio and first twitch tension of TOF (T1), and determined their relationship during recovery from rocuronium-induced neuromuscular blockade at various concentrations of sugammadex. Methods: Tissue specimens of the phrenic nerve-diaphragm were obtained in 60 adult Sprague-Dawley rats. Each specimen was immersed in an organ bath filled with Krebs buffer solution and stimulated with the TOF pattern using indirect supramaximal stimulation at 20-second intervals. After a 30-minute stabilization period, rocuronium loading and booster doses were serially administered at 10-minute intervals in each sample until > 95% depression of T1 was confirmed. Specimens were randomly allocated to either the control group (washout) or to one of the five sugammadex concentration groups (SGX0.75, SGX1, SGX2, SGX4, and SGX8, respectively). Recovery from neuromuscular blockade was monitored using T1 and TOF ratio simultaneously until the recovery of T1 to >95% and that of TOF ratio to >0.9. Results: Statistically significant intergroup differences were observed between the recovery patterns of T1 and the TOF ratio (TOFR, p<0.050), except between SGX2 and SGX4. TOFR/T1 values were maintained at nearly 1 in the control, SGX0.75, and SGX1 groups; however, those were exponentially decayed in the SGX2, SGX4, and SGX8. Conclusions: Recovery of the TOF ratio may be influenced by the sugammadex dose, and TOF ratio of 1.0 may be achieved before full T1 recovery if administration of sugammadex exceeds that of rocuronium.