Anesthetic requirements for halothane in young children 0-1 month and 1-6 months of age.

In a previous study, the authors found that infants, in the first 6 months of life, required the highest minimum alveolar concentration (MAC) of any age group (1.09% halothane). Because only two 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, the authors determined 1) whether the MAC of halothane in neonates (n = 12) differs from that in infants (1-6 months of age) (n = 12) and 2) whether the blood pressure and heart rate responses in neonates differ from those in infants at approximately 1 MAC. The authors found that the MAC of halothane in neonates, 0.87% +/- 0.03 SEM, was significantly lower (P less than 0.01) than that in infants, 1.20% +/- 0.06 SEM. With induction of anesthesia, the systolic blood pressure decreased 23% in neonates (P less than 0.05) and 34% in infants (P less than 0.005) from awake values. Similarly, the heart rate decreased 12% in neonates and 22% in infants (P less than 0.05). The incidence of hypotension (greater than 30% decrease in systolic blood pressure from awake) in neonates, 33%, was not significantly different from that in infants, 44%. The authors conclude that 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 approximately 1 MAC of halothane.