Evaluation of the combined effect of remifentanil and desflurane on blood pressure during induction of anesthesia using response surface model.

Background and Goal of Study: High initial concentration of inspired desflurane (DES) after intravenous induction of anesthesia can increase blood pressure (BP) significantly. To attenuate this response, opioids are commonly used with DES during induction. We conducted this study to evaluate DES and remifentanil drug interaction during anesthetic induction using response surface model (RSM). 

Materials and Methods: Hospital Ethics Committee approval and patients’ informed consents were obtained. RSM with the central composite design was employed and the fourteen combination groups with 5 patients in each were produced. After intravenous induction with propofol, patients received REMI infusion (effect site concentration, 1-3 ng/ml) and DES inhalation (inhaled dial settings, 3.7-6.2 vol%) at various concentration pairs. BPs measured shortly before endotracheal intubation were taken for analysis. 

Results and Discussion: Fig. 1. The RSM graph describes the combined effect of REM-DES on mean arterial blood pressure just before endotracheal intubation. 
The result was in accordance with our clinical observations that higher BP produced as the initial concentration of DES increased. REMI concentration between 1-2 ng/ml, the decrement of DES concentration effectively lowered BP, but this could result in insufficient anesthesia. REMI effect site concentration between 2-3 ng/ml, the increment of REMI concentration efficiently reduced BP in the studied range of DES concentration.

Conclusion(s): RSM demonstrates that DES has predominant effect on the BP where REMI effect concentration lies between 1-2 ng/ml and REMI takes over this dominance where concentration between 2-3 ng/ml.

Evaluation of combined effect of remifentanil and desflurane on blood pressure during anesthesia induction using response surface model