Age-dependent cardiovascular effects of halothane anesthesia in neonatal pigs

The cardiovascular effects of halothane anesthesia in a mixture of nitrous oxide and oxygen were studied on piglets 7 hr to 25 days of age. Blood pressure, heart rate and peripheral flows were recorded simultaneously in all animals. Body temperature and blood gas composition and pH were monitored and maintained within normal physiological limits for piglets. Inspired halothane concentration was kept at 1.0% during vascular surgery and then increased or decreased systematically. Halothane anesthesia depressed mean aortic pressure and increased carotid, femoral and renal resistances in piglets less than one week of age. These effects increased with increasing halothame concentrations from 0.25% to 1.5%. In older animals, mean aortic pressure changes were significant only at halothane concentrations above 1.0%, while peripheral resistances were unaffected. Although there was no concentration-dependent change in heart rate in either age group, heart rates were consistenly faster in younger animals.