Abstract:

Objective To investigate the effect of sevoflurane on neuromuscular blockade of cisatracurium in general anesthesia in the elderly. Methods Forty patients with ASA Ⅰ-Ⅱ undergoing elective surgery were randomly divided into elderly group (aged no less than 65) and adult group (aged between 18 and 65), and each group was randomly divided into sevoflurane group and propofol group, with 10 patients in each group. Anaesthesia was induced with midazolam, propofol, fentanyl and lidocaine aerosol. After induction, sevoflurane groups were maintained with 1.73% sevoflurane, and propofol groups were with 4-6 mg/kg propofol per hour. Thirty minutes later, 50 μg/kg cisatracurium was administered (20 μg/kg for the first injection, 10 μg/kg for the next three injections). Four myopalmus (amplitudes T1, T2, T3 and T4) was induced by train-of-four (TOF) stimulation, and neuromuscular monitoring was conducted. The time of onset after drug administration and maximum block effect were recorded, cumulative dose-effect curves for cisatracurium were determined, and 50% and 95% effective doses (ED50 and ED95) were obtained. After the last drug administration, the duration of recovery to 25% T1, 75% T1 and 90% T1 (T125%, T175% and T190%), duration of recovery to 70% TOF (TOF70%) and recovery index (RI) were recorded. Results ED50 of cisatracurium in elderly sevoflurane group, elderly propofol group, adult sevoflurane group and adult propofol group were 28.51 μg/kg, 33.47 μg/kg, 26.16 μg/kg and 31.77 μg/kg respectively, and ED95 of cisatracurium in these groups were 50.93 μg/kg, 59.86 μg/kg, 48.69 μg/kg and 55.43 μg/kg respectively. ED50 and ED95 of cisatracurium in sevoflurane groups were significantly lower than those in corresponding propofol groups (P<0.05). However, ED50 and ED95 in elderly groups were not significantly different from those in adult groups under the same condition of anesthesia (P>0.05). There was no significant difference in the time of onset of cisatracurium among groups (P>0.05). RI in sevoflurane groups were longer than those in corresponding propofol groups, and RI in elderly groups were longer than those in adult groups under the same condition of anesthesia (P<0.05). T125%, T175%, T190% and TOF 70% in elderly sevoflurane group were significantly longer than those in the other groups (P<0.05), and T125%, T175%, T190% and TOF 70% in adult sevoflurane group were significantly longer than those in adult propofol group (P<0.05). Conclusion Compared with total intravenous anesthesia, ED50 and ED95 of cisatracurium is significantly reduced and duration of recovery from the block is significantly prolonged after anesthesia with sevoflurane inhalation. Under the same condition of anesthesia, elderly patients may experience much longer duration of recovery from the block than adult patients.

Key words: cisatracurium, sevoflurane, dose-effect curve, propofol