In this study, the optimal effect-site concentration of remifentanil for blunting hemodynamic responses to endotracheal intubation during total intravenous anesthesia using propofol were evaluated.

137 ASA class I and II patients, aged 18-60 years, were randomly allocated to one of six groups according to the effect-site concentration of remifentanil. Remifentanil was then infused at a target effect-site concentration of 0, 1, 2, 3, 4 or 6 ng/ml in groups R0, R1, R2, R3, R4 and R6, respectively. Anesthesia was induced with propofol infusion at a target effect-site concentration of 4 µg/ml endotracheal intubation was performed 5 minutes after remifentanil administration. Blood pressure (BP), heart rate (HR) and cardiac index (CI) were recorded at the baseline and then every 30 seconds until 3 minutes after intubation.

BP and HR in groups R0, R1 and R2 increased significantly after intubation when compared with the baseline values. The CI in group R0 also increased significantly after intubation when compared with the baseline values. Incidences of hypertension and hypotension were 50% and 5% in R0, 32% and 14% in R1, 18% and 32% in R2, 10% and 48% in R3, 8% and 54% in R4, and 0% and 81% in R6. There were also 2 cases in which the mean blood pressure was less than 50 mmHg in group R6.

We suggest that the optimal target effect-site concentrations of remifentanil for blunting hemodynamic responses to endotracheal intubation are 3 or 4 ng/ml during total intravenous anesthesia using propofol at an effect-site concentration of 4 µg/ml.