제왕절개술시 Propofol 목표농도주입의 평가와 약동학적 변화 = Evaluation of Target - controlled Infusion and Pharmacokinetic Changes of Propofol during Cesarean Section

다국어 초록 (Multilingual Abstract)

Background: Propofol has been used for the induction and maintenance agent of general anesthesia for cesarean section, but the pharmacokinetics of propofol will be different from in case of non-pregnancy. In order to evaluate the performance of computer-assisted continuous infusion (CACI) system and pharmacokinetic changes of propofol during cesarean section under general anesthesia, we measured the plasma concentrations of propofol, and compared those with the predicted plasma concentrations.
Methods: Sixty pregnant women who received cesarean section under general anesthesia were studied. After the titration of adequate post-delivery target propofol concentration with bispectral index in twenty pregnant women, forty women were randomly assigned into the two different groups. In group I, after preoxygenation, anesthesia was induced with thiopental 4 ㎎/㎏ and succinylcholine 1 ㎎/㎏, and intubation was done. Vecuronium 0.1 ㎎/㎏ Ⅰ.Ⅴ. was administered for muscle relaxation, and mechanical ventilation was maintained with EtCO_2 between 30-35 ㎜Hg. Anesthesia was maintained with N_2O/O_2 (2:2 L/min) with enflurane before delivery, meanwhile, 3.5 ㎍/㎖ propofol target-controlled infusion (TCI) and 1.0 ng/㎖ fentanyl TCI with air/O_2 (2:2 L/min) were maintained after delivery. In group Ⅱ, anesthesia was induced with propofol (2.0 ㎎/㎏) and maintained with 3.5 ㎍/㎖ propofol TCI and air/O_2 (2:2 L/min), and after delivery the target concentration of propofol 5.0 ㎍/㎖ and 1.0 ng/㎖ fentanyl TCI were maintained. The bispectral index were monitored perioperatively. The plasma propofol concentrations were measured at 10 minute intervals and the predicted concentrations were evaluated with the performance errors (PE).
Results: The target concentrations (Cp, 95% confidence interval) that could maintain 50% and 95% of patients hemodynamically stable with the bispectral index within 40 - 60 after delivery were 3.7 (3.20 - 3.92) ㎍/㎖ and 5.0 (4.67 - 5.74) ㎍/㎖ for propofol when it had been started since the induction of anesthesia. In group 1, the measured concentrations of propofol at 10 minute intervals after delivery were, 2.61 ± 0.74, 2.51 ± 0.60 and 2.23 ± 0.64 ㎍/㎖, and the median absolute performance errors (MAPE's) were 25.4%, 28.7% and 37.1% respectively. In group Ⅱ, the measured concentration at delivery was 1.94 ± 0.54 ㎍/㎖, and after delivery 2.38 ± 1.22, 2.11 ± 0.97 and 1.86 ± 1.04 ㎍/㎖ and the MAPE's were 39.1%, 52.8%, 60.2% and 63.0% respectively. The maximally increased bispectral index after the induction of anesthesia until delivery was significantly higher in group 1.
Conclusions: It was concluded that CACI using the pharmacokinetic model of propofol for nonpregnancy could not provide the predicted target plasma concentrations with a sufficient accuracy in case of patients who received cesarean section under general anesthesia. But the measured propofol concentrations were enough to maintain an adequate sedation level for the cesarean section under general anesthesia with monitoring the bispectral index.