BACKGROUND: Clinical observations suggest the immaturity of the neonate'sability to respond appropriately to cardio-respiratory challenges and tilt test could help in detectingautonomic dysfunction in neonates. MATERIAL/METHODS: Heart rate (HR) responses following a 45 degreeshead-up tilt during sleep were measured within the first week of adjusted age in 7 healthy full-termneonates, 7 healthy preterm infants and 5 neonates with abstinence syndrome. RESULTS: The tilt and thereturn to the horizontal position generally provoked a sustained or transient tachycardia, or a flatresponse in healthy full-term neonates and in preterm neonates, but a sustained or transient bradycardiain neonates with abstinence syndrome. CONCLUSIONS: When compared to previous studies in older infants,our data point to the immaturity of the neonate's ability to respond appropriately to cardio-respiratorychallenges. No difference is noted between full-term and preterm neonates. The altered HR response inneonates with abstinence syndrome suggests an autonomic dysregulation in this group.

Keywords: Bradycardia, Heart Rate, Heroin Dependence, Infant, Newborn, Infant, Premature, Research Support, Non-U.S. Gov, Tilt-Table Test