Blood pressure rhythms during the perinatal period in very immature, extremely low birthweight neonates

The aim of this study was to investigate if blood pressure (BP) rhythms wer e present in the perinatal period in very immature infants. Twenty-two infa nts, median gestational age 24-28 weeks, who had indwelling arterial lines with undamped arterial BP waveforms, were studied. The infants were all rec eiving intensive care under constant conditions. The hourly mean, systolic and diastolic BPs on days 2 and 7 were examined. A cosinor analysis of the mean BP was performed examining period lengths of 4, 8, 12, 16, 20, and 24 h to determine whether ultradian and/or circadian rhythms existed. On day 2 , but not day 7, the mean and systolic BPs showed significant variation and circadian and ultradian rhythms were demonstrated. We suggest that materna l influences may be responsible for the BP rhythms noted in very immature i nfants on day 2. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved .