A comparative observational study on the effect of two different doses of fentanyl on the effect site concentration of propofol during induction of anesthesia using clinical assessment score and bispectral index

Abstract Background and Aims: Opioids are known to reduce the propofol dose required to blunt movement and hemodynamic responses to noxious stimuli. However, the optimal propofol dosage for smooth induction remains unclear, particularly in the Indian population where pharmacokinetic data is limited. This study aims to evaluate the effect site concentration of propofol in conjunction with varying fentanyl doses, with relation to loss of consciousness and bispectral index (BIS) values during anesthesia induction using target-controlled infusion (TCI). Material and Methods: Sixty patients aged 20–50 years, with American Society of Anesthesiologists physical status I and II, scheduled for elective surgeries under general anesthesia were included. Anesthesia induction was performed using a TCI pump with propofol based on the Schnider model, starting at 1.5 μg/ml and increasing at 0.5 μg/ml until loss of verbal response, followed by 0.2 μg/ml till the final clinical endpoint was reached. Patients received either 1 or 2 μg/kg fentanyl or no fentanyl. Endpoints were assessed using the BIS monitor and Modified Observer Assessment of Alertness/Sedation Scale score. Results: Hemodynamic parameters were stable across groups. The effect site concentration of propofol for loss of response to noxious stimuli was significantly lower in the fentanyl groups (fentanyl 1 μg/kg- 2.90 ± 0.1947 μg/ml, fentanyl 2 μg/kg- 2.445 ± 0.23 μg/ml) compared to the propofol alone group (4.205 ± 0.909 μg/ml) ( P = 0.0001). Similar results were observed for loss of response to verbal commands. The effect site concentration at BIS 60 corresponded to loss of response to noxious stimuli. Conclusions: Propofol effect site concentrations were significantly higher without fentanyl. The findings contribute valuable data for refining pharmacokinetic models tailored to individual patient needs.