Tracheal intubating conditions using propofol and remifentanil target-controlled infusions

Using target-controlled infusions (TCI) we aimed to determine the most appropriate dose of remifentanil required for intubation, using a steady effect-site concentration of propofol and without the use of neuromuscular blocking drugs. Sixty ASA III patients presenting for elective surgery were randomly allocated to one of three groups. Anaesthesia was induced in all patients using a target-controlled infusion of propofol 6.5 microg x ml(-1). This was reduced to 3 microg x ml(-1) after 1 min. Each group received a different TCI of remifentanil, 19, 15 or 11 ng x ml(-1), which was reduced to 10, 8 or 6 ng x ml(-1), respectively, after 1 min. Laryngoscopy and intubation were attempted at 4 min. Laryngoscopy and ease of intubation were assessed using a standard scoring system. Intubation was considered satisfactory in 75% of patients in groups 1 and 2 and 35% of patients in group 3. Intubation was successful in 20/20, 19/20 and 15/20 patients in groups 1, 2 and 3, respectively. Pulse oximetry, heart rate and noninvasive arterial pressure were measured pre-induction, and at intervals until after laryngoscopy and intubation. Mean arterial pressure (MAP) and heart rate decreased following induction of anaesthesia in all groups, which was statistically significant. Following laryngoscopy, MAP and heart rate increased, but were significantly less than the corresponding baseline values.