Cardiovascular autonomic regulation in preterm infants: the effect of atropine.
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 approximately 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.
Máxima Medical Center, Neonatal Intensive Care Unit, Veldhoven, P.O. Box 7777, 5500 MB, The Netherlands. P.Andriessen@mmc.nl
Peter
P
Andriessen
Ben J A
BJ
Janssen
Ralph C M
RC
Berendsen
S Bambang
SB
Oetomo
Pieter F F
PF
Wijn
Carlos E
CE
Blanco
D001285:Atropine / Q000008:administration & dosage*; D001341:Autonomic Nervous System / Q000187:drug effects* / Q000502:physiology*; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000502:physiology*; D018727:Muscarinic Antagonists / Q000008:administration & dosage*; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology
D018727:Muscarinic Antagonists; D001285:Atropine