The time course of potentiation of rocuronium by sevoflurane versus isoflurane

Objective: To investigate the time course of potentiation of rocuronium produced by1 MAC of sevoflurane or isoflurane.Methods: Fifty-four ASA Ⅰ—Ⅱ male patients aged18-60 years undergoing elective abdominal operation under general anesthesia were studied.Anesthesia was induced with midazolam 0.1 mg·kg-1,fentanyl 4ug·kg-1 and propofol 2～4mg·kg-1.Tracheal intubation was facilitated with rocuronium 0.6 mg·kg-1iv.The degree of neuromuscular block was monitored by measuring muscle response to TOF using accelerography(HXD—Ⅰ).For maintenance of anesthesia the patients were randomly assigned to receive either propofol+fentanyl(Control group) or 1 MAC of sevoflurane(Sevo group) or 1MAC of isoflurane(Iso group).Rocuronium was continuously infused during operation to maintain T1at 5% of the control and the infusion rate was recorded every 15 min.Results: In Sevo and Iso groups the infusion rate of rocuronium was reduced in an exponential manner and maximal potentiation occurred at 90 min of isoflurane or sevoflurane inhalation.The maximal reduction in infusion rate was 44.3% in Sev group and 38.9% in Iso group.There was no significant difference between the two groups.Conclusions: Sevoflurane and isoflurane can potenriate the muscle relaxation produced by rocuronium in a similar degree and the potentiation is time dependent.