Single-breath vital capacity high concentration sevoflurane induction in children: with or without nitrous oxide?

Single-breath vital capacity inhalation induction with high concentration sevoflurane (SBVC-HC) is a rapid and 'needleless' technique, preferred and well tolerated in the cooperative child. The addition of nitrous oxide may speed up induction by its second gas effects. Previous studies done in children looking at the effect of N(2)O on this technique lacked power and showed conflicting results. This study aims to investigate the effect of N(2)O on induction time for SBVC-HC sevoflurane induction in children.

Eighty unpremedicated, ASA I and II children, aged 5-15 yr having elective surgical procedures under general anaesthesia, were recruited and randomized to: Group A: 8% sevoflurane in O(2) 6 litre min(-1), and Group B: 8% sevoflurane in N(2)O 4 litre min(-1) and O(2) 2 litre min(-1). The primary outcome was the time to 'loss of eyelash reflex'. The time to return of 'regular respiration' and 'conjugate gaze' were also noted.

The difference in the 'time to loss of eyelash reflex' was small but statistically significant. Group B: mean duration 53.6 s, standard deviation (SD) 16.1, compared with Group A: 63.5 s, SD 16.1 (mean difference 9.9, 95% confidence interval 2.5-17.3, P=0.01). Differences in the time to return of 'regular breathing' and 'conjugate gaze' were not statistically significant. Patients receiving N(2)O had less excitatory movements (P=0.007), but incidence of other adverse events was low and did not differ significantly between both groups. More than 94% of children would choose this method of induction again in both groups.

We conclude that for SBVC-HC sevoflurane induction in children, the addition of N(2)O resulted in faster loss of consciousness and reduced excitatory movements.