The determinants of propofol induction time in anesthesia

Area of Science:

• Anesthesiology
• Pharmacology
• Physiology

Background:

• Anesthetic dose requirements are typically lower in patients with reduced cardiac output (CO).
• Elevated CO can decrease anesthetic blood concentration during induction and maintenance.
• High CO might also accelerate anesthetic delivery to the brain, affecting induction time.

Purpose of the Study:

• To assess the time required for anesthesia induction using propofol via target-controlled infusion (TCI).
• To investigate factors influencing propofol pharmacodynamics, including cardiac output, age, and lean body mass.

Main Methods:

• Cardiac output (CO) and blood volume (BV) were measured using dye densitometry.
• Propofol was administered via TCI to achieve a target plasma concentration of 3 µg/ml.
• Time to reach Bispectral Index (BIS) values of 80 and 60 was recorded; age, sex, and lean body mass (LBM) were analyzed.

Main Results:

• High CO significantly reduced the time to reach the initial endpoint (BIS 80) (P=0.020).
• Age and LBM significantly prolonged the time to reach the secondary endpoint (BIS 60) (P=0.001).
• Propofol plasma concentration (Cp) at 10 minutes showed a negative correlation with blood volume (BV) (P=0.020).

Conclusions:

• Cardiac output is a significant predictor of early anesthesia induction time.
• Age and LBM are significant factors influencing the later stages of anesthesia induction.
• Propofol's pharmacodynamics are complexly influenced by CO, age, and LBM.