Many reports with hypnotics and opiates have been published for nonrelaxant tracheal intubation. In addition to its immediate onset and short duration time, remifentanil can well prevent responses against short and strong stimulation like tracheal intubation. However, the high concentration of remifentanil for nonrelaxant tracheal intubation can cause hemodynamic instability, thus we tried to estimate the predicted effect-site concentration of remifentanil for smooth intubation and provoking hypotension.

Forty three ASA I and II patients were randomly selected to receive an effect-site-controlled infusion of remifentanil 0, 2, 4, 6 ng/ml and propofol 2 mg/kg. Trachea was intubated after 3 minutes of manual breathing support with desflurane 6 vol%. The vital signs, end-tidal concentration of desflurane and responses of patients were recorded before intubation for 3 minutes and until 2 minutes after intubation every minute. The effective effect-site concentration (ECe) was calculated at 95% successful rate of smooth intubation and at 50% of provoking hypotension (equal to or under 55 mmHg).

The estimation results of the logistic regression stated that 95% ECe of remifentanil for smooth intubation was 8.0 (5.0??4.3) ng/ml and 50% ECe for provoking hypotension equal to or under 55 mmHg before intubation was 5.0 (2.6??.7) ng/ml.

Remifentanil at 8.0 ng/ml provided good conditions for smooth intubation without muscle relaxants but could provoked hypotension. Consequently, we recommend the careful observation of the blood pressure with the use of remifentanil and the evaluation of the suitable measures to maintain the blood pressure for nonrelaxant tracheal intubation.