THE PHARMACOLOGY OF SEVOFLURANE IN INFANTS AND CHILDREN

Background: Sevoflurane is a new volatile anesthetic with physical pro perties that should make it suitable for anesthesia in children. In th is study, the minimum alveolar concentration (MAC) of sevoflurane in o xygen alone and in 60% nitrous oxide, the hemodynamic, induction and e mergence responses to sevoflurane and the metabolism to inorganic fluo ride were studied in 90 ASA physical status 1 or 2 neonates, infants, and children. Methods: MAC of sevoflurane in oxygen was determined in six groups of subjects stratified according to age: full-term neonates , infants 1-6 and > 6-12 months and children > 1-3, > 3-5 and > 5-12 y r. MAC in 60% nitrous oxide was determined in a separate group of chil dren 1-3 yr of age. After an inhalational induction, the trachea was i ntubated (except for neonates in whom an awake intubation was performe d). MAC for each age group was determined using the Up-and-Down techni que of Dixon. Results: MAC of sevoflurane in neonates, 3.3 +/- 0.2% an d in infants 1-6 months of age, 3.2 +/- 0.1%, were similar; MAC in old er infants 6-12 months and children 1-12 yr was constant at approximat e to 2.5%; MAC of sevoflurane in 60% nitrous oxide in children 1-3 yr of age was 2.0 +/- 0.2%. Systolic arterial pressure decreased signific antly at 1 MAC before skin incision compared with awake values in all subjects except children 1-3 yr with 60% nitrous oxide and children 5- 12 yr in oxygen, and then returned toward awake values after skin inci sion. Heart rate was unchanged at approximate to 1 MAC sevoflurane bef ore incision compared with awake values in all subjects except childre n > 3-5 and > 5-12 yr in whom heart rate increased before incision. In duction of anesthesia, particularly with respect to airway irritabilit y, and emergence from sevoflurane anesthesia were not remarkable. The plasma concentration of inorganic fluoride reached maximum values (8.8 -16.7 mu M) 30 min after discontinuation of anesthesia. Conclusions: W e conclude that sevoflurane appears to be a suitable anesthetic agent for use in neonates, infants and children undergoing less than or equa l to 1 h of anesthesia.