Objective To evaluate the effect of obesity on the potency of propofol for sedation.Methods Sixty patients of both sexes, aged 35-55 yr, of American Society of Anesthesiologists physical status Ⅰ or Ⅱ , scheduled for elective operation under general anesthesia, were enrolled in the study.The patients were divided into 2 groups (n=30 each) according to the body mass index (BMI) : normal body weight (BMI ＜ 25 kg/m2) group (group C) and obesity (BMI 30-40 kg/m2) group (group O).No patients received premedication.Propofol was given by target-controlled infusion.The initial target plasma concentration of propofol was set at 1.2 μg/ml.After the target concentration was steadily maintained for 30 s, it was increased in 0.3 μg/ml increment until the patients lost consciousness (OAA/S score =1).The target plasma concentration of propofol was recorded during each period.The median effective concentration (EC50) and 95％ confidence interval of propofol for loss of consciousness was calculated using probit analysis.Results The EC50 and 95％ confidence interval of propofol for loss of consciousness were 3.82 (3.73-3.90) and 3.29 (3.20-3.37) μg/ml in group C and group O, respectively.Compared with group C, the EC50 was significantly decreased in group O (P＜0.05).Conclusion Obesity can enhance the potency of propofol for sedation.

Carcinoma, Non-Small-Cell Lung/genetics* ; Drug Resistance, Neoplasm/genetics* ; ErbB Receptors/metabolism* ; Genomic Instability ; Humans ; Lung Neoplasms/genetics* ; Neoplasm Proteins/metabolism* ; Protein Kinase Inhibitors/therapeutic use*