Background: Enflurane is one of the most commonly used inhaled anesthetics in China, but its requirement to block adrenergic responses after skin incision in pediatric patients is still unknown. This study was to determine the minimum alveolar anesthetic concentration (MAC) of potent inhaled anesthetics required to blunt the adrenergic response to skin incision of enflurane (MAC_BAR) in infants and children. 

Methods: Twenty-eight patients, 10 infants (6-12 months) and 18 young children (1-6 years), were studied. The 18 children were randomly assigned into two groups, with or without fentanyl. Anesthesia was induced with 3 mg/kg propofol and 0.15 mg/kg vecuronium, and maintained with enflurane in 100% oxygen. Fentanyl (3 μg/kg) was given intravenously 5 minutes before incision for the patients of fentanyl group. The "up and down" method (with 0.3 MAC as a step size and 1 MAC as the start dose) was applied to determine MAC_BAR. The response was considered positive if the mean arterial pressure (MAP) or heart rate (HR) increased ≥15% after incision. The MAC_BAR was calculated as the mean of four independent cross-over responses in each group.

Results: MAC_BAR of enflurane in children of 1-6 years old was 3.2% (95% CI, 2.8%-3.6%) and was reduced to 2.2% (95% CI, 1.8%-2.5%) by 3 μg/kg fentanyl. In infants of 6-12 months old, the MAC_BAR of enflurane was 3.4% (95% CI, 3.0%-3.8%).

Conclusions: MAC_BAR of enflurane in infants older than 6 months is similar to that in young children. The MAC_BAR of enflurane decreases with co-administration of fentanyl in the pediatric population.

Key words: anesthesia; children; enflurane; infants

                    World J Pediatr 2008;4(1):49-52