Circadian blood pressure pattern in full-term newborn infants

A fully automatic noninvasive device (Dinamap) was used for monitoring blood pressure (BP) and heart rate repetitively over 48 h in 21 full-term newborn infants (9 males and 12 females), aged 4 days in order to clarify the occurrence of a circadian rhythm (CR). The data collected were analyzed by computer statistical analysis. Mean values and standard error of BP and heart rate measured at hourly intervals in males and females were computed and plotted as chronograms. However, each newborn infant was analyzed for a CR of BP and heart rate by the single cosinor fit of a 24-hour cosine curve. The analysis of the chronograms revealed that the values of systolic and diastolic BP show an hour-by-hour significant fluctuation in male infants, but not in female infants. CR development of BP is present only in a minority of newborn infants and reveals sex and interindividual differences. CR of heart rate is absent in all infants. The physiological significance of these findings was discussed, and the importance of knowing the physiological variances of BP in infants in order to obtain a correct clinical evaluation was stressed.