The peak bispectral index time cannot predict early phase propofol pharmacodynamics with effect site-controlled...

Area of Science:

• Pharmacology
• Anesthesiology
• Pharmacokinetics

Background:

• The plasma-effect site equilibration rate constant (ke0) for propofol is crucial for accurate drug delivery.
• Previous studies determined ke0 based on peak bispectral index (BIS) time (T(PEAK)).
• The performance of ke0 with effect site-controlled infusion algorithms requires further evaluation.

Purpose of the Study:

• To assess the performance of the propofol ke0 derived from T(PEAK) within an effect site-controlled infusion algorithm.
• To compare the accuracy of two different ke0 values (based on T(PEAK) = 74s and T(PEAK) = 96s) in predicting propofol's effect.

Main Methods:

• Forty patients were randomized into two groups (TE1 and TE2) using Schnider's pharmacokinetic model with different ke0 adaptations.
• Stage 1 involved effect-site concentration (Ce) controlled infusion; Stage 2 used plasma concentration controlled infusion after BIS recovery.
• Propofol Ce at loss of responsiveness (LOR), lowest BIS, and hysteresis loops were analyzed to evaluate ke0 performance.

Main Results:

• Significant differences in calculated propofol Ce at LOR were observed between Stage 1 and Stage 2 in both groups (P<0.01).
• Mean lowest BIS values were significantly higher in Stage 1 compared to Stage 2 (P<0.05).
• Propofol Ce versus BIS plots demonstrated apparent hysteresis loops, indicating model-related discrepancies.

Conclusions:

• The study could not clinically validate the accuracy of ke0 derived from T(PEAK) = 74s using the Schnider propofol pharmacokinetic model.
• The findings suggest potential limitations in applying this specific ke0 value for precise propofol infusion control.
• Further research is needed to refine pharmacokinetic models and ke0 estimations for optimal anesthetic management.