The appropriate dose of propofol for anesthesia induction in morbidly obese patients

BACKGROUND: To investigate the optimal dose of propofol in patients with morbid obesity when the anesthetic induction dosage is calculated based on lean body weight (LBW). METHODS: Forty morbid obese patients with body mass index (BMI) ≥35 kg/m2 were randomly divided into two groups: B and M. The sequential method was used in group B to study the EC50 and 95% confidence interval (CI) that met a bispectral index (BIS) value of <50 (the initial dose was set at 2.5 mg/kg). The sequential method was used in group M to obtain the EC50 and 95% CI (the initial dose was set as 3.0 mg/kg) satisfying the mean arterial pressure (MAP) fluctuation margin of >40%. The optimal dose interval of propofol was obtained by synthetically analyzing the results of the two-sequence method. RESULTS: There was no significant difference in the general condition between the two groups (P>0.05). There was no significant change in vital signs from when patients entered the operating room to when sufentanil was infused (P>0.05). The probit model of group B was Y=-5.411+2.343X, the EC50 of positive reaction with BIS <50 was 2.310 mg/kg, and 95% CI was 1.850-2.883 mg/kg. The probit model in the M group was Y=3.275 - 0.918X, the EC50 of positive reaction that reached >40% of the whole process of anesthetic induction was 3.567 mg/kg, and 95% CI was 1.233-7.165 mg/kg. CONCLUSIONS: The appropriate dosage of propofol was 2.310-3.567 mg/kg when the anesthetic induction dosage for patients with morbid obesity was calculated based on LBW. With this dose, the depth of intubation is satisfactory and the hemodynamics are stable.