[Influence of obesity on pharmacokinetics and pharmacodynamics of isoflurane].

OBJECTIVE

To observe the effect of obesity on pharmacokinetics and pharmacodynamics of isoflurane.

METHODS

Twenty-six patients undergoing cholecystectomy were divided into obese group (Group A, BMI > or = 27, n = 13) and normal body weight group (Group N, BMI < or = 24, n = 13) according to body mass index (BMI). All patients were given to the same isoflurane anesthesia. Inspired and end-expired concentrations of isoflurane were monitored and uptake fraction of isoflurane were calculated.

RESULTS

Isoflurane concentrations of vaporizer in Group A [(1.8 +/- 0.3)%] were evidently higher than those in Group N [(1.5 +/- 0.1)%] at all observed points (P < 0.05 or P < 0.01). Uptake fraction of isoflurane in Group A were higher than those in Group N at observed points (P < 0.05, P < 0.01 or P < 0.001), but there were no differences in the time when isoflurane concentration was lowered to 50% and awake time between the two groups after discontinuing inhaling isoflurane.

CONCLUSIONS

Obese patients demand higher inspired concentration and uptake of isoflurane than those in normal weight patients but discharge of isoflurane was influenced by obesity within the observed period of (66 +/- 33) min.