Standardized oculocardiac reflex in ex-premature near full term (93 cases)

The aim of the study was to present data investigating vagal reactivity in a population of premature infants reaching term, using the oculo-cardiac reflex. Ninety three premature infants, free of any disease, near full term at the moment of testing, were prospectively investigated at a time close to discharge from neonatal unit. After an all-night polygraphic recording, a standardized oculo-cardiac reflex test was performed during quiet sleep. Data were classified in relation to both chronological and postconceptional ages. Simple liner regression analyses were performed on the selected variables. The results showed heterogeneity of the vagal response in this population: longest asystole (1049 ms +/- 540; 95th percentile = 1894 ms); maximal percentage of deviation between two successive RR intervals (88% +/- 90; 95th percentile = 200%); and duration between the beginning of decrease in heart rate and return to mean heart rate (14 s +/- 10; 95th percentile = 30 s). Our healthy premature infants at time of discharge exhibited a wider range of vagal reactivity than previously reported for the full term newborns. Considering our findings, we recommend caution before proceeding with treatment of vagal bradycardia in a similar premature infant population.