Predicting Propofol Induction Dose.Kazama et al. (page 205)

Using pulse dye densitometry measurements to calculate cardiac output, blood volume, mean transit time, dye clearance, and central blood volume, Kazama et al. evaluated different variables for the ability to predict propofol induction dose at constant infusion rates of 40 mg · kg−1 · h−1 as a function of lean body mass. The study group included 75 unpremedicated patients (aged 10–85 yr), all scheduled to undergo intravenous induction of anesthesia for elective surgery.

In addition to these variables, patient characteristics, such as lean body mass, sex, age, hemoglobin concentration, and hepatic blood flow also were analyzed to determine their relation, if any, to induction dose. On the study day, a bolus injection of 0.3 mg/kg indocyanine green dye, 2.5 mg/ml, was administered to each patient. Researchers obtained dye densitogram measurements while patients rested on the operating table. The researchers then administered a flush of 20 ml lactated Ringer’s solution. Propofol induction then proceeded with the drug infused at 40 mg · kg−1 · h−1 while level of consciousness was evaluated. Induction time was defined as the time from propofol administration until the patient did not responded to gentle verbal and physical stimulation; the induction dose was the amount of propofol administered up to this point. After consciousness was lost, the propofol infusion rate was decreased to 4 mg · kg−1 · h−1.

Univariate least squares linear regression analysis was used to analyze the relation between propofol induction dose and each of the patient characteristics. Stepwise multiple linear regression models were used to select important predictors of induction dose.

Although the researchers found a significant correlation between induction dose and each of the eight variables evaluated, only age, lean body mass, and hepatic blood flow were associated independently with induction dose. At the infusion rate used in this study, the researchers concluded that propofol induction dose could be determined with use of the variables of age, lean body mass, central blood volume, and hepatic blood flow.