End-tidal sevoflurane concentration for tracheal intubation and minimum alveolar concentration in pediatric patients

Sevoflurane is a new inhalational anesthetic agent having low solubility in blood and a relatively nonpungent odor. As such it should be useful as an inhalation induction in pediatric patients. The objectives of the study were to determine both the minimum alveolar concentration (MAC) and the concentration required for tracheal intubation (MACEI) of sevoflurane in pediatric patients.

The study group consisted of 36 ASA physical status 1 elective surgical patients, aged 1-9 yr. MACEI determination: After establishing and maintaining the end-tidal concentration for 15 min, tracheal intubation was attempted with an uncuffed tracheal tube without neuromuscular relaxants or other adjuvants. Each concentration at which tracheal intubation was attempted was predetermined according to the up-and-down method (with 0.5% as a step size). MAC determination: The patients examined were the same as those for MACEI determination except that for the exclusion of those to whom neuromuscular relaxants or other adjuvants drugs were administered. End-tidal sevoflurane concentration was determined according to the up-and-down method (with 0.5% as a step size) and held constant for at least 15 min before a skin incision.

MACEI of sevoflurane was 2.69% (95% fiducial limits: 2.23% and 3.37%); MAC of sevoflurane was 2.03% (95% fiducial limits: 1.51% and 2.53%); and the MACEI/MAC ratio was 1.33.

Sevoflurane appears to be suitable for use in pediatric patients as an induction agent, permitting tracheal intubation without neuromuscular relaxants.