Background: The underlying mechanism as to why some hypotensive preterm infants do not respond to inotropic medications remains unclear. For these infants, we hypothesize that impaired vasomotor function is a significant factor and is manifested through a decrease in low-frequency blood pressure variability across regulatory components of vascular tone. Methods: Infants born 28 weeks estimated gestational age underwent prospective recording of mean arterial blood pressure (MABP) for 72h after birth. After error-correction, root mean square (RMS) spectral power was calculated for each valid 10-min data frame across each of four frequency bands (B1-0.005-0.0095 Hz, B2-0.0095-0.02 Hz, B3-0.02-0.06 Hz, and B4-0.06-0.16) corresponding to different components of vasomotion control. Results: 40 infants (29 normotensive control, 11 inotrope-exposed) were included with a meanSD EGA of 25.21.6 weeks and birthweight 790211 grams. 9.7/11.8 million (82%) data points were error-free and used for analysis. Spectral power across all frequency bands increased with time, although the magnitude was 20% less in the inotrope-exposed infants. A statistically significant increase in spectral power in response to inotrope initiation was noted across all frequency bands. Infants with robust blood pressure response to inotropes had a greater increase as compared to those who had limited or no blood pressure response. Conclusions: In this study, hypotensive infants who require inotropes have decreased low-frequency variability at baseline, when compared to normotensive infants, which increases after inotrope initiation. Low-frequency spectral power does not change for those with inotrope treatment failure, suggesting dysfunctional regulation of vascular tone as a potential mechanism of treatment failure.
- blood pressure
- spectral analysis
- Copyright © 2017, Journal of Applied Physiology