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Katoh T, Kobayashi S, Suzuki A, Kato S, Iwamoto T, Bito H, Sato S. British Journal of Anaesthesia 2000; 84:63-66.

Review: This study prospectively evaluated the effect of intravenous fentanyl on MAC-BAR of sevoflurane in children. The MAC-BAR is the minimum alveolar concentration of inhalation agent that blocks adrenergic responses to skin incision. 61 healthy ASA 1 patients aged 2-6 years scheduled for surgery under general anesthesia were randomized into one of 3 groups; 0, 2, or 4 mcg/kg fentanyl bolus. After a standard inhalation induction with sevoflurane and nitrous oxide, patients received sevoflurane at a preselected end-tidal concentration according to an up-downdesign and 60% nitrous oxide. The fentanyl bolus was given 5 minutes before skin incision. Heart rate and mean arterial pressure were recorded before 1 minute before fentanyl administration, 1 minute before skin incision, 30 seconds to 1 minute after incision and 5 minutes after incision.

The MAC-BAR of sevoflurane was 1.45 MAC (95% CI 1.25-1.65) in the absence of fentanyl. Fentanyl 2mcg/kg and 4 mcg/kg decreased MAC-BAR to 0.63 MAC (95% CI 0.55-0.72) and 0.38 MAC (95% CI 0.33-0.44) respectively.

Comments: The results of this study are not surprising. In fact, the use of fentanyl to decrease MAC-BAR has been shown in adults with multiple agents. However, in contrast to the adult literature, no ceiling effect was noted with a 2mcg/kg dose of fentanyl in this pediatric study. This may suggest that a ceiling effect to fentanyl may not occur in children with small doses of fentanyl. Finally, and most importantly, this study demonstrates that a balanced anesthetic technique in children can decrease inhaled anesthetic requirements and optimize hemodynamics during routine cases.

Reviewed by: Jeffrey Galinkin, MD
Childrens Hospital of Philadelphia