BACKGROUND: Recently obesity population is epidemically rapidly increasing. But, in the anesthetic field the study for obesity patients is not good enough. So, we designed the study to see the effect of obesity on awareness in general anesthesia with propofol.

METHODS: The 52 subjects were between 20 to 60 years old and ASA physical status 1, 2 undergoing general anesthesia for elective surgery. According to asia pacific obesity criteria, we divided the patients into the obesity group (BMI ≥ 25) and the non-obesity group (BMI < 25). Propofol was infused using TCI for induction and maintenance. BIS was used for monitoring the depth of anesthesia. During operation, we tried to keep BIS between 40-49 by manipulate the target concentration of TCI. After the operation, without stimulating patients, we measured the time (T-BIS₅₀₇₀) from the BIS passes 50 then goes to 70. We compare the T-BIS₅₀₇₀ between the obesity and the non-obesity group.

RESULTS: The obesity and the non-obesity group do not show significant difference in age, sex, height, body temperature, anesthesia time, and total used propofol amounts. BMI in obesity group was 27.3 ± 1.9 kg/m² and in non-obesity group was 22.2 ± 1.8 kg/m². T-BIS₅₀₇₀, the awareness time was significantly different between the obesity group (170.3 ± 54.8 sec) and the non-obesity group (212.7 ± 81.8 sec).

CONCLUSIONS: Our data suggest that in general anesthesia with propofol the obesity group's awareness time is shorter compared with the non-obesity group and the effects may come from the uniqueness of the propofol's pharmacokinetics and the obesity patient's physical characteristics.