title: Minimal alveolar concentration of sevoflurane inhibiting the reflex pupillary dilatation after noxious stimulation in children and young adults.
abstract: BACKGROUND
  In children, sevoflurane is the most commonly used anaesthetic. Its excellent haemodynamic tolerance gives it a wide therapeutic index. This halogenated agent can abolish movement [minimal alveolar concentration (MAC)] or haemodynamic responses (MACBAR) to noxious stimulus in children as in adults. Reflex pupillary dilatation (RPD) has been demonstrated as a very sensitive measure of noxious stimulation. In order to investigate the effect of sevoflurane on the RPD, a subcortical reflex, we determined the MAC of sevoflurane inhibiting the RPD in 50% of the subjects in response to skin incision (MACpup) in pre- and post-pubertal subjects.
  
  
  METHODS
  We included 30 pre-pubertal children and 19 post-pubertal subjects. Patients received sevoflurane at preselected concentrations according to an 'up and down' design, and after a steady-state period, skin incision was performed. The RPD was considered as significant when the pupillary diameter increased by more than 100%. Heart rate (HR) and bispectral index (BIS) changes were analysed according to the pupillary response.
  
  
  RESULTS
  The MACpup of sevoflurane was 4.8% (95% confidence interval, 4.6-5.1%) in pre-pubertal children vs 3.4% (3.5-3.3%) in post-pubertal subjects (P<0.001). Inhibition of RPD was always associated with lack of significant HR response. In pre-pubertal children receiving high concentrations of sevoflurane, RPD in response to noxious stimulation was frequently associated with lack of HR response and low BIS values.
  
  
  CONCLUSIONS
  MACpup was higher than MAC and close to the MACBAR. Inhibition of RPD in pre-pubertal children required higher sevoflurane concentrations compared with post-pubertal subjects, suggesting that the relationship between the brain structure sensitivities may differ with brain maturation.
authors.affiliation: Department of Anesthesiology,  Armand Trousseau Hospital, AP-HP, UPMC, Paris,  France.
authors.forename: E
authors.initials: E
authors.lastname: Bourgeois
authors.forename: N
authors.initials: N
authors.lastname: Sabourdin
authors.forename: N
authors.initials: N
authors.lastname: Louvet
authors.forename: F X
authors.initials: FX
authors.lastname: Donette
authors.forename: M L
authors.initials: ML
authors.lastname: Guye
authors.forename: I
authors.initials: I
authors.lastname: Constant
mesh_terms: D000293:Adolescent; D000367:Age Factors; D000704:Analysis of Variance; D000768:Anesthesia, General; D018685:Anesthetics, Inhalation / Q000493:pharmacokinetics / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D018592:Cross-Over Studies; D062109:Dermatologic Surgical Procedures; D004305:Dose-Response Relationship, Drug; D004569:Electroencephalography / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007223:Infant; D008738:Methyl Ethers / Q000493:pharmacokinetics / Q000494:pharmacology*; D016343:Monitoring, Intraoperative / Q000379:methods; D011446:Prospective Studies; D011650:Pulmonary Alveoli / Q000378:metabolism*; D012025:Reflex, Pupillary / Q000187:drug effects*; D000077149:Sevoflurane
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane