The relationship between serum progesterone concentration and anesthetic and analgesic requirements: A prospective observational study of parturients undergoing cesarean delivery

Background: In clinical practice, pregnant women have lower anesthetic requirements for general anesthesia than nonpregnant women. Although the hormonal changes such as progesterone associated with pregnancy may affect the minimum alveolar concentration of volatile anesthetics, the relationship between the anesthetic or analgesic requirements and progesterone level in fullterm women has not been studied. In this study, we attempted to identify relationships between anesthetic or analgesic requirements and maternal serum concentrations of progesterone.

Methods: We studied 100 parturients >36 weeks' gestation who were scheduled for planned cesarean delivery under general anesthesia. Venous blood was collected to measure the maternal progesterone concentration. Anesthesia was induced with 4 to 5 mg/kg thiopental and 0.8 mg/kg rocuronium. During anesthetic maintenance, sevoflurane 0.5% to 2.0% and nitrous oxide 50% in oxygen were titrated based on arterial blood pressure, heart rate, and bispectral index value. Vital signs, bispectral index, end-tidal sevoflurane concentration, and sevoflurane consumption per hour were recorded. Visual analog scale pain scores and cumulative analgesic consumption were recorded at 2, 24, and 48 hours postoperatively.

Results: The mean serum progesterone concentration was 128.2 ± 83.0 ng/mL. There was a significant negative correlation between sevoflurane consumption per hour and serum progesterone concentration (Pearson correlation r =-0.26; 95% confidence interval,-0.44 to-0.05, P = 0.01). Cumulative analgesic consumption at postoperative hours 2 (r =-0.20, P = 0.05), 24 (r =-0.25, P = 0.02), and 48 (r =-0.28, P = 0.01) were correlated inversely with serum progesterone concentration. Women with high progesterone levels (higher than the median value) had lower sevoflurane consumption per hour (P = 0.02) and 48-hour postoperative cumulative analgesic consumption (P = 0.02) than women with low (below the median value) levels.

Conclusions: The decreased anesthetic and analgesic requirements of near full-term parturients might partially depend on serum progesterone concentration.