Evaluating Midazolam's Influence on Bispectral Index and Propofol Concentrations Using Schnider and Eleveld Models in...

Area of Science:

• Anesthesiology
• Pharmacology
• Neuroscience

Background:

• Midazolam is a common anesthetic, but its combined effects with propofol on Bispectral Index (BIS) and propofol concentration at the effector site (CeP) require further investigation.
• Understanding these interactions is crucial for optimizing total intravenous anesthesia (TIVA) using target-controlled infusion (TCI).

Purpose of the Study:

• To investigate the pharmacodynamic interaction between midazolam and propofol in TIVA-TCI.
• To compare the effects of midazolam on BIS and CeP using the Schnider and Eleveld pharmacokinetic models.

Main Methods:

• Prospective study of breast surgery patients undergoing TIVA-TCI.
• Assessment of BIS and CeP at loss of responsiveness, maintenance, and return of responsiveness.
• Recording of unwanted anesthesia events like unwanted spontaneous responsiveness (USRE), burst suppression episodes (BSuppE), and postoperative delirium (POD).

Main Results:

• Midazolam premedication decreased propofol dosage and CeP at loss of responsiveness and maintenance, but not at return of responsiveness.
• Model-specific effects observed: Schnider model showed reduced total propofol dose, Eleveld model showed lower BIS at loss of responsiveness.
• Unwanted anesthesia events occurred in 36.2% of patients; BSuppE rates were lower in the Schnider model and decreased with midazolam in the Eleveld model.

Conclusions:

• Midazolam premedication modulates CeP and BIS in TIVA-TCI, with variations dependent on the pharmacokinetic model.
• These findings suggest potential for optimizing propofol administration and improving patient outcomes in TIVA-TCI.
• Model selection is important for accurately predicting and managing anesthetic depth with midazolam and propofol.