Relation between initial blood distribution volume and propofol induction dose requirement.

Area of Science:

• Anesthesiology
• Pharmacokinetics
• Clinical Pharmacology

Background:

• Propofol induction dose is highly variable, influenced by factors like distribution volume and disposition.
• Predicting the accurate propofol dose is crucial for safe and effective anesthesia induction.

Purpose of the Study:

• To investigate if pre-administration blood distribution volumes, cardiac output (CO), and hepatic blood flow (HBF) can predict the propofol induction dose.
• To identify key patient characteristics that influence the required propofol dose for loss of consciousness.

Main Methods:

• Determined propofol dose for loss of consciousness in 75 patients (age 11-85) using a constant infusion rate per lean body mass (LBM) of 40 mg x kg(-1) x h(-1).
• Measured cardiac output (CO), blood volume (BV), central blood volume (CBV), and hepatic blood flow (HBF) using indocyanine green pulse spectrophotometry.
• Employed univariate and stepwise multiple linear regression to analyze the relationship between propofol induction dose and patient variables.

Main Results:

• Significant correlations were found between propofol induction dose and age, sex, LBM, hemoglobin, CO, BV, CBV, and HBF.
• Age, LBM, CBV, and HBF were independently associated with the propofol induction dose, explaining 85% of the variance (R2 = 0.85).

Conclusions:

• The propofol induction dose, at a constant infusion rate relative to LBM, can be reliably determined using four key variables: age, LBM, CBV, and HBF.
• This finding aids in optimizing propofol dosing for patients with American Society of Anesthesiologists physical status I or II.