We wanted to determine an adequate combination of target effect-site concentrations of remifentanil and propofol during anesthetic induction with target controlled infusion (TCI). We also determined whether increasing remifentanil concentrations might reduce propofol consumption at loss of consciousness (LOC).

Sixty ASA 1 or 2 patients were randomly allocated according to the target effect-site concentration of remifentanil and propofol (R7P3: remifentanil 7 ng/ml + propofol 3 µg/ml, R5P4: remifentanil 5 ng/ml + propofol 4 µg/ml, R3P5: remifentanil 3 ng/ml + propofol 5 µg/ml). After the target effect-site concentration of remifentanil had been reached, the TCI of propofol was started. The effect-site concentration of propofol at LOC was recorded. When the target effect-site concentration of propofol was reached, 0.6 mg/kg of rocuronium was administered. Tracheal intubation was performed after 2 minutes. The noninvasive blood pressure, heart rate (HR), bispectral index (BIS), and infused dose of remifentanil and propofol were recorded.

R3P5 groupd showed a significant increase in mean blood pressure after intubation (104 ± 31.9 mmHg, P < 0.05) compared to R7P3 and R5P4. BIS at the time when propofol reached its target effect-site concentration was significantly higher in the R7P3 group (71.6 ± 9.9, P < 0.05 compared to R5P4 and R3P5). There was a significant relationship between the effect-site concentration of remifentanil and propofol at LOC (Y = 2.032 - 0.351X, R² = 0.551, P < 0.0001).

The R5P4 target effect-site concentrations are adequate dosing combinations during TCI induction based on hemodynamic responses and BIS values.