Abstract
Introduction: The baroreceptor reflex (BR) is the most prominent short-term compensator during blood pressure (BP) challenges.
Aim: To study the effect of postconceptional age (PCA, gestational age + postnatal age) on baroreceptor reflex sensitivity (BRS) in 32 infants (PCA, range: 28–42 wk) during quiet sleep state in the first days after birth.
Method: Cross-spectral power analysis between systolic blood pressure (SBP) and R-R fluctuations, using fast Fourier transform, was estimated in a low frequency (LF, 0.04–0.15 Hz), high frequency (HF, individualized between p-10 and p-90 value of respiratory frequency), and total frequency band (0.04–1.5 Hz). BRS was estimated using transfer function analysis (transfer gain or BRS, ms/mmHg; phase, s) between LF fluctuations of SBP and R-R.
Results: With PCA the mean R-R interval and LF-, HF-, and total spectral power of R-R interval series increased significantly. PCA significantly correlated with LF transfer gain (BRS = 1.1 x PCA - 30 ms/mmHg, r = 0.80, p < 0.01). Median BRS was 4.6 (IQR, 3.1–5.4), 7.5 (IQR, 5.2–10.1) and 15.0 (IQR, 11.8–19.7) ms/mmHg for infants with a PCA between 28–32 wk (n=16), 32–37 wk (n=10), and 37–42 wk (n=6), respectively. For LF transfer phase no differences between PCA groups were found: SBP fluctuations lead R-R interval changes by approximately 3 s. BRS correlated significantly with LF-, HF-, and total spectral power values of the R-R interval series. By contrast, BRS did not show a significant correlation with the spectral values of SBP series.
Conclusion: This study demonstrates that the capability of the BR to buffer spontaneous occurring BP fluctuations by R-R interval changes is limited in very preterm infants, but increases with PCA. An immature BR function may contribute to conditions that predispose to cerebral hemorrhagia/ischemia in the preterm infant. BR maturation with gestation seems to be an effect of progressive parasympathetic activity.
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Andriessen, P., Oetomo, S., Peters, C. et al. 9 Baroreceptor Reflex Function in Newborns: The Effect of Postconceptional Age. Pediatr Res 58, 355 (2005). https://doi.org/10.1203/00006450-200508000-00038
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DOI: https://doi.org/10.1203/00006450-200508000-00038