MINIMUM ALVEOLAR CONCENTRATION OF DESFLURANE AND HEMODYNAMIC-RESPONSES IN NEONATES, INFANTS, AND CHILDREN

We sought to determine the minimum alveolar concentration (MAC) and hemodynamic responses to desflurane in 72 fasting and unpremedicated full-term neonates, infants, and children up to 12 yr of age. The patients were divided into six groups (n - 12) according to age. After awake tracheal intubation, neonates were anesthetized with desflurane in oxygen and air. Infants > 1 month of age and all older children were anesthetized with desflurane in 100% oxygen, and their tracheas were intubated without muscle relaxation. MAC was determined using the "up-and-down technique" and logistic regression. Heart rate and systolic arterial pressure were recorded awake, at almost-equal-to 1 MAC desflurane before skin incision and at almost-equal-to 1 MAC during the peak hemodynamic responses to skin incision. We found that the relationship between MAC (mean +/- standard deviation) as determined by the up-and-down technique and age was quadratic, reaching a maximum value in infants 6-12 months of age: in neonates 0-1 month MAC was 9.16 +/- 0.02%, in infants 1-6 months 9.42 +/- 0.06%, in infants 6-12 months 9.92 +/- 0.44%, in children 1-3 yr 8.72 +/- 0.59%, in children 3-5 yr 8.62 +/- 0.45%, and in children 5-12 yr 7.98 +/- 0.43%. MAC values obtained using logistic regression were similar. Heart rate decreased an average of 16% before skin incision in infants 6-12 months of age and children 1-3 and 3-5 yr of age when compared to awake values (P < 0.025) but did not change significantly in the remaining three groups. Heart rate returned to or was greater than awake values after incision in all groups. Systolic arterial pressure decreased significantly before skin incision in all groups (P < 0.05) but returned toward awake values after incision. We conclude that 1) the MAC of desflurane in infants and children depends on age, although the difference between the MAC in neonates and that in older infants is much smaller than that reported previously with both halothane and isoflurane and 2) hemodynamic responses to almost-equal-to 1 MAC desflurane are similar in neonates, infants, and children up to 12 yr of age.