Adequate Target Concentration of Propofol and Fentanyl for Total Intravenous Anesthesia by Target-controlled Infusion during Cesarean Section

Min, Sang Kee; Yoo, Eun Sook; Kim, Jin Su; Kim, Sang Hyun; Han, Sang Gun

Abstract

BACKGROUND: Propofol has been used for the induction and maintenance of obstetric anesthesia for its potential benefit of rapid recovery and less post-anesthetic complications. In order to determine the safe application of target-controlled infusion of propofol and fentanyl during Cesarean section under general anesthesia, we have investigated the adequate target concentrations of each drug using the bispectral index and hemodynamic parameters.
METHODS
Ninety-two pregnant women who received Cesarean section under general anesthesia were enrolled in this study. After preoxygenation, anesthesia was induced with thiopental 4 mg/kg and succinylcholine 1 mg/kg, and intubation was done. Vecuronium 0.1mg/kg I.V. was applied for muscle relaxation, and mechanical ventilation was maintained with N2O/O2 (2 L/2 L)-enflurane. EtCO2 was maintained between 30 35 mmHg. After delivery of the fetus, propofol and fentanyl was infused by a computer-assisted continuous infusion system with air/O2 (2 L/2 L). The bispectral index was monitored perioperatively. This study proceeded in three stages. In the first stage, thirty women were studied for titration of the target effect-site concentration of propofol that could maintain a bispectral index between 40 60 while maintaining the target concentration of fentanyl at 1.5 ng/ml. In the second stage, forty-two women were randomly assigned into the four different groups (F25, F50, F75, F100) at target fentanyl concentrations of fentanyl of 0.25, 0.50, 0.75 and 1.0 ng/ml for each group respectively. The adequate target concentration of fentanyl was titrated. In the third stage, twenty women were studied for assessment of the adequacy of target concentrations of propofol and fentanyl prospectively.
RESULTS
The target effect-site concentrations (Ce, 95% confidence interval) that could maintain 50% and 95% of patients hemodynamically stable with the bispectral index within 40-60 were 2.41 (2.27-2.55) microgram/ml and 3.15 (2.95-3.50) microgram/ml for propofol, 0.32 (0.13-0.46) ng/ml and 0.84 (0.66-1.29) ng/ml for fentanyl. The pre-anesthetic bispectral index was 97.1+/-1.2 and it decreased maximally to 39.5+/-6.47 after thiopental injection and increased maximally to 83.6+/-6.3 before delivery and it was 80.6+/-6.9 for eye-open to verbal command during recovery.
CONCLUSIONS
The adequate target effect-site concentrations of propofol and fentanyl for the maintenance of total intravenous anesthesia during Cesarean section were determined and these concentrations were validated prospectively.