Fentanyl-oxygen versus fentanyl-N₂O/ oxygen anaesthesia in children undergoing cardiac surgery

Fentanyl-oxygen (fentanyl-02) anaesthesia was compared to fentanyl-nitrous oxide/oxygen (fentanylN₂0I0₂) anaesthesia in 14 children undergoing cardiac surgery. Children were randomly assigned to one of the two techniques studied, with seven patients in each group. The mean age (mean ± SE) was 3.9 ±0.75 years (0.5-8.25 years) and mean weight 14.7 ± 2 kg (3.5- 29.5 kg). Patients were premedicated with IM atropine 0.02 mg'kg'^-1 and morphine 0.2 mg·kg'^-11 hour preoper-atively. They received a fentany I bolus of 30 μg·kg'^-1 with a concomitant continuous infusion of 0.3μg·kg^-1·min^-1. Pancuronium 0.l mg·kg^-1 was administered immediately following the fentanyl bolus. Fifty per cent nitrous oxide was given with oxygen in one group and 100 per cent oxygen was administered to the other group. Fentanyl plasma concentrations were similar in the two groups at the various stages of surgery. There were no significant differences between the two treatment groups in systolic and diastolic blood pressure or in heart rate in response to induction, intubation, and incision. There was a significantly greater increase in systolic blood pressure after sternotomy in thefentanyl-O₂ group, in addition, in six of seven patients recieving fentanyl-O₂ there were events of sudden increase in blood pressure during various stages of surgery before the bypass, necessitating an additional fentanyI bolus or the addition ofdroperidol in four cases. Similar phenomena were not documented in the fentanyl-N₂OIO₂ group. Our studies suggest that fentanyl-O₂ anaesthesia in the schedule described, in children undergoing elective cardiac surgery for Tetralogy of F allot, A-V canal, and transposition of the great arteries, is not sufficient to prevent elevation in systolic blood pressure despite fentany I plasma concentrations in excess of 20 mg·ml^-1. The addition of nitrous oxide prevents this phenomenon.