For halothane or isoflurane, the minimum alveolar concentration (MAC) is greatest in which group?

For halothane or isoflurane, the minimum alveolar concentration (MAC) is greatest in which group?

• A. Premature infant 30 weeks postconceptual age
• B. Full-term neonate
• C. 3-month-old infant
• D. 19-year-old male bodybuilder

Answer: (C)

MAC reflects how much of an inhaled anesthetic is needed to prevent movement to a painful stimulus; a higher MAC means the drug is less potent at that age. Age strongly influences MAC for halothane and isoflurane: in the youngest patients, MAC tends to be higher, then it changes with maturation. For these agents, early infancy sits at a peak range where the CNS and cerebral metabolism respond differently to anesthetics, so the amount required to blunt a response is relatively high. Among the groups listed, a 3-month-old infant falls in that early infancy window where MAC is typically at its highest compared with a full-term neonate (who is younger and often has a different maturation profile), a premature infant (who is even more immature and can have different CNS sensitivity), and a young adult who generally has a lower MAC. Therefore, the 3-month-old infant is the group with the greatest MAC for halothane or isoflurane.

MAC reflects how much of an inhaled anesthetic is needed to prevent movement to a painful stimulus; a higher MAC means the drug is less potent at that age. Age strongly influences MAC for halothane and isoflurane: in the youngest patients, MAC tends to be higher, then it changes with maturation. For these agents, early infancy sits at a peak range where the CNS and cerebral metabolism respond differently to anesthetics, so the amount required to blunt a response is relatively high.

Among the groups listed, a 3-month-old infant falls in that early infancy window where MAC is typically at its highest compared with a full-term neonate (who is younger and often has a different maturation profile), a premature infant (who is even more immature and can have different CNS sensitivity), and a young adult who generally has a lower MAC. Therefore, the 3-month-old infant is the group with the greatest MAC for halothane or isoflurane.