Effect of bolus dose of remifentanil on haemodynamic response to tracheal intubation

A randomized placebo-controlled double-blinded study was conducted in 40 ASA 1 and 2 patients to determine the dose response of remifentanil in attenuating the haemodynamic response to tracheal intubation. Patients were allocated to one of four groups: placebo, remifentanil 1 microgram.kg-1, remifentanil 2 micrograms.kg-1 and remifentanil 4 micrograms.kg-1. A propofol target-controlled infusion was started at 4 micrograms.ml-1 and incrementally titrated to loss of verbal contact. Muscle relaxation was provided by cisatracurium. The study drug was given three minutes later over 30 seconds, and 90 seconds later the patient's trachea was intubated under direct laryngoscopy. Baseline noninvasive blood pressure and heart rate recordings were made prior to starting target-controlled infusion, then at one-minute intervals after loss of verbal contact for the duration of the study. Demographic data and target-controlled infusion rate at intubation was similar for the groups. Following intubation, heart rate increased by 15% in the placebo group, 10% in 1 microgram.kg-1 group, with no changes in 2 micrograms.kg-1 and 4 micrograms.kg-1 groups. Systolic blood pressure following intubation increased by 30% in the placebo group, 10% in the 1 microgram.kg-1 group and remained unchanged in the 2 micrograms.kg-1 and 4 micrograms.kg-1 groups. Remifentanil 1 microgram.kg-1 attenuated the rise in heart rate and systolic blood pressure. Remifentanil 2 micrograms.kg-1 blocked the haemodynamic response completely: no further benefit was shown from increasing the dose to 4 micrograms.kg-1.