The Effect of Remifentanil on the Loss of Consciousness during Propofol Infusion

Abstract

Background: General anesthesia is a balance between hypnosis and analgesia. Remifentanil is often combined with propofol to both induce and maintain total intravenous anesthesia. This study evaluated the effect of remifentanil on the propofol requirements for a loss of consciousness. Methods: Forty adult patients with ASA 1 or 2 were enrolled in this study. The patients were randomly given either saline or remifentanil before the induction of anesthesia with an infusion of propofol, 15 mg/kg/h. In the remifentanil group, all the patients received a computer controlled infusion of remifentanil with a effect site concentration of 4 ng/ml. The times required for the patient to lose consciousness, the propofol requirements and the bispectral index at the loss of consciousness to verbal commands were recorded. Results: In the remifentanil group, loss of consciousness was attained significantly faster and with lower propofol doses than in the saline group. The bispectral indices were significantly higher at loss of consciousness in the remifentanil group. Conclusions: A remifentanil infusion before the induction of propofol anesthesia significantly reduces the propofol requirements for the loss of consciousness. Remifentanil enhances the hypnotic effect of propofol.