Objective: To determine the effect of pregnancy on blood/gas partition coefficient (B/G) of volatile anesthetics and to evaluate the relation between B/G and blood component concentration.
Methods: Blood samples were obtained from four groups of fasting women: 8 nonpregnancies, 8 first-trimester pregnancies, 12 mid-trimester pregnancies, 12 third-trimester pregnancies. B/G of desflurane, isoflurane and halothane in each subject was measured by double equilibration technique. Red blood cell (RBC), hemoglobin concentration (Hb), hematocrit (HCT) and the serum concentration of cholesterol (Chol), triglyceride (TG), albumen (Alb), globulin (Glob) were measured.
Results: 1. There was no significant difference in B/G of desfluraneand and in B/G of halothane among the four groups. There was significant difference in B/G of isoflurane; the lowest B/G was in the mid-trimester and the highest B/G was in the third trimester of pregnancy. The trend direction of halothane among four groups was similar to that of isoflurane, although no significant difference was observed therein. 2. RBC, Hb and HCT showed statistically significant difference among the four groups, which decreased to the lowest level in the mid-trimester and came up slightly in the third trimester. There was statistically significant difference in Alb, A/G, TG and Chol among the four groups. Alb and A/G were the lowest and TG, Chol were the highest in the third-trimester of pregnancy. 3. There was a correlation between the serum TG and the B/G of halothane. The B/G of isoflurane correlated directly with serum TG and Hb. The B/G of desflurane correlated directly with Chol.
Conclusion: The above findings indicated that pregnancy brought on alterations in the blood components and serum components, thus inducing the difference in B/G between the flaoride volatile anesthetics. During pregnancy, the B/G of isoflurane altered significantly more than that of halothane did, whereas no significant alteration in the B/G of desflurane was noted.