BACKGROUND: Laryngoscopic tracheal intubation causes acute hemodynamic changes such as hypertension and tachycardia. Adjuvant opioids during induction have been used to attenuate such responses. The aim of this study was to determine the optimal dose of bolus remifentanil, a newly developed ultra short acting opioid, to suppress cardiovascular responses immediately after laryngoscopic endotracheal intubation in patients anesthetized with N₂O-O₂-sevoflurane.

METHODS: Sixty ASA I or II patients who requiring endotracheal intubation were randomly allocated to one of the four groups; C, R0.5, R1, and R2. Each group received normal saline, 0.5, 1, or 2µgram/kg of remifentanil respectively. Predetermined drugs for each group were administered over 30 seconds after induction of anesthesia with thiopental, rocuronium and 2 vol% of sevoflurane with 50% nitrous oxide. Laryngoscopic endotracheal intubation was carried out 60 seconds after the study drug administration. Mean arterial pressure (MAP) and heart rate (HR) were recorded at pre-anesthesia (PA), pre-intubation (PI) and during 5 minutes after intubation (IT-1 to IT-5). Statistical analysis was done for comparison of time and dose dependent changes among the groups.

RESULTS: Baseline values were similar among the groups. IT-1 values did not change compared to PI values in R1 and R2. However, MAP and HR in R2 were significantly lower than PA values during post-intubation period.

CONCLUSIONS: Bolus injection of 1µgram/kg of remifentanil blocks MAP and HR elevation after laryngoscopic endotracheal intubation without adverse effects in patients under N₂O-O₂-sevoflurane anesthesia.