Optimal remifentanil dosage for providing excellent intubating conditions when co-administered with a single standard dose of propofol

This dose-response study aimed to determine the dose of remifentanil combined with propofol 2.5 mg.kg(-1) which provided excellent intubation conditions in 95% of patients. Ninety premedicated female ASA 1 and 2 patients were randomly allocated to five remifentanil dose groups (1, 2, 3, 4 or 5 mu g.kg(-1)). Induction of anaesthesia was performed with a blinded dose of remifentanil infused over 60 s simultaneously co-administered with propofol 2.5 mg.kg(-1) infused over 45 s. Tracheal intubation was attempted 150 s after the beginning of induction. Intubating conditions were assessed with the Copenhagen score. A probit analysis was performed to calculate the intubating efficient doses (IED) of remifentanil in 95% of patients (IED(95)). Our data revealed that the IED(95) of remifentanil was 4.0 (95% CI: 3.4- 5.6) mu g.kg(-1), which was associated with a maximum decrease in heart rate and mean arterial pressure of < 30%, a finding which also applied to the other groups.