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

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).

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.

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.

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.