Continuous infusion of remifentanil combined with target-controlled infusion of propofol for tracheal intubation in dogs

Ninety dogs presenting for elective surgery were randomly assigned into three groups of 30. Intubation conditions, haemodynamic responses and other events were evaluated following target controlled infusion (TCI) with propofol at 3.0 mu g/ml, combined with variable infusion rates of remifentanil (R1 0.1 mu g/kg/minute, R2 0.2 mu g/kg/minute, R3 0.3 mu g/kg/minute). Tracheal intubation was recorded as excellent, good or poor according to jaw relaxation, tongue withdrawal, ease of laryngoscopy, swallowing, coughing and limb movement. Excellent overall intubation conditions were present in 5/30 (17 per cent), 12/30 (40 per cent) and 21/30 (70 per cent) of dogs in groups R1-3, respectively. In all three groups, the mean arterial pressure (MAP) and mean heart rate (MHR) decreased following induction of anaesthesia. Following intubation, despite an increase in MAP and MHR values, they remained significantly lower than baseline values. Muscle twitching and involuntary movement was observed after propofol induction in 10 dogs. The results suggest that a plasma concentration of 3 mu g/ml propofol along with an infusion rate of remifentanil at 0.3 mu g/kg/minute may provide satisfactory conditions for intubation, while avoiding major adverse haemodynamic effects.