Anesthetic Requirements for Halothane in Young Children 0–1 Month and 1–6 Months of Age

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Abstract
Infants, in the first 6 mo. of life, require the highest minimum alveolar concentration (MAC) of any age group (1.09% halothane). Because only 2 neonates (0-31 days of age) were included in the original study and because profound depression of blood pressure and heart rate have been reported in neonates, it was determined whether the MAC of halothane in neonates (n = 12) differs from that in infants (1-6 mo. of age) (n =12), and whether the blood pressure and heart rate responses in neonates differ from those in infants at .apprx. 1 MAC. The MAC of halothane in neonates (0.87% .+-. 0.03 SEM [standard error of the mean]) was significantly lower (P < 0.01) than that in infants (1.20% .+-. 0.06 SEM). With induction of anesthesia, the systolic blood pressure decreased 23% in neonates (P < 0.05) and 34% in infants (P < 0.005) from awake values. The heart rate decreased 12% in neonates and 22% in infants (P < 0.05). The 33% incidence of hypotension (> 30% decrease in systolic blood pressure from awake values) in neonates was not significantly different from that in infants (44%). The MAC of halothane in neonates is 25% less than that in infants and significantly less than was thought previously. The MAC in infants is the highest of any age group. The decrease in blood pressure and the incidence of hypotension in neonates are similar to those in infants at .apprx. 1 MAC of halothane.