To study cardiovascular autonomic control, we assessed the effect of atropine on heart rate (HR) and blood pressure (BP) variability in 12 preterm infants (range 26–32 wk) before intubation for respiratory insufficiency. Spectral power analysis of R-R interval and systolic BP (SBP) series were estimated in a low-frequency (LF; 0.04–0.15 Hz) and high-frequency (HF;0.4 –1.5 Hz) band and evaluated for a 10-min period before and a 10-min period after atropine sulfate (0.01 mg/kg). Baroreceptor reflex (BR) functioning was estimated using transfer function analysis at LF (coherence, gain, and phase). Atropine resulted in a significant 12% increase in steady-state HR (p ?? 0.01) and unchanged SBP. For R-R interval series, the total spectral power decreased 6-fold (p ?? 0.01), which was predominantly due to a reduction in the LF band (16-fold; p ?? 0.01). In contrast, we observed a significant increase (25%; p ?? 0.05) in total spectral power of SBP series partly as a result of an increase in HF power. The LF power of SBP series was not altered. The median LF transfer gain (BR sensitivity) between SBP and R-R interval decreased from 4.2 to 1.4 ms/mm Hg (p ?? 0.01) after atropine. The LF phase relationship (BP leads R-R interval fluctuations by ~4 s) was not changed after atropine. In conclusion, even in preterm infants in distress, atropine modulates HR and BP variability, suggesting that BR-mediated parasympathetic control of heart rate is of significance for cardiovascular control at that age.
|Number of pages||8|
|Publication status||Published - 2004|