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Using alfentanil followed by an anesthetic induction dose of propofol provides adequate conditions for tracheal intubation without neuromuscular relaxants.Remifentanil, which has a clinical onset similar to that of alfentanil, has not been investigated for this indication. Accordingly, 80 ASA physical status I and II premedicated outpatients were randomly assigned to one of four groups (n = 20/group). Remifentanil 1, 2, 3, or 4 micro g/kg (Groups I-IV, respectively) was infused intravenously over 90 s. Sixty seconds after beginning the remifentanil infusion, propofol 2 mg/kg was infused over 5 s. Ninety seconds after the administration of propofol, laryngoscopy and tracheal intubation were attempted and graded. Clinically acceptable intubating conditions (i.e., jaw relaxed, vocal cords open, and fewer than two coughs in response to intubation) were observed in 35%, 75%, 100%, and 95% of patients in Groups I-IV, respectively. Clinically acceptable intubating conditions were significantly (P < 0.05) less likely to occur in Group I compared with all other groups. Excellent intubating conditions (i.e., vocal cords open, no movement in response to intubation) were observed in 30%, 50%, 80%, 80% of patients in Groups I-IV, respectively. Overall conditions at intubation were significantly (P < 0.05) better in Groups III and IV compared with Groups I and II. The mean time to resumption of spontaneous ventilation after induction was <5 min in all groups. No patient manifested clinically significant muscle rigidity. The mean arterial pressure decreased 16%, 20%, 28%, 26% immediately before tracheal intubation in Groups I-IV, respectively. No patient was treated for hypotension or bradycardia. In conclusion, healthy, premedicated patients with favorable airway anatomy can be reliably intubated with good or excellent conditions 90 s after the administration of remifentanil 3-4 micro g/kg and propofol 2 mg/kg. Implications: Remifentanil 3 micro g/kg and propofol 2 mg/kg co-administered intravenously may reliably provide adequate conditions for tracheal intubation in healthy patients without neuromuscular relaxants. This combination of drugs may allow the rapid return of spontaneous ventilation.