The Effect of Propofol on Isolated Human Pregnant Uterine Muscle

Background: Propofol is an alternative to thiopental as an intravenous induction agent for cesarean section. Because it has relaxant effects on vascular and other smooth muscles, the authors set out to determine whether propofol has any effect on pregnant human uterine smooth muscle in an isolated preparation.

Methods: Myometrial specimens were excised from 10 parturients undergoing elective cesarean section. The muscle strips were suspended in tissue baths and isometric tension was recorded. After establishment of rhythmic contractions in the buffer solution as a control, propofol (0.5 to 10 [micro sign]g/ml) in fat emulsion was applied cumulatively to the bath. The effect of the fat emulsion at equivalent concentrations was also examined.

Results: Propofol concentrations of 2.7 x 10-6 M (0.5 [micro sign]g/ml) and 1.1 x 10-5 M (2 [micro sign]g/ml) had no significant effect on the active tension developed by muscle contraction. However, propofol at concentration of 5.5 x 10-5 M (10 [micro sign]g/ml) reduced the active tension by 45% (P < 0.02) compared with the control value. The fat emulsion had no effects on the active tension.