Influence of prematurity on postnatal maturation of heart rate and arterial pressure responses to hypoxia in lambs.
BACKGROUND
While hypoxic events with bradycardias are a frequent occurrence during the first weeks of life in preterm infants, the impact of preterm birth on maturation of the cardiovascular response to hypoxia in early postnatal life is unknown.


OBJECTIVE
In the present study, we tested the hypothesis that preterm birth influences postnatal maturation of cardiovascular responses to hypoxia.


METHODS
6 preterm lambs (term 132 days, birth weight 2.9 kg) and 6 full-term lambs (term 147 days, birth weight 4.3 kg) were studied without sedation on days 3, 7, 14, 21 and 28 during acute, steady-state hypoxia (FIO(2) = 0.08, 15 min).


RESULTS
Results show that full-term lambs increased their heart rate (HR) in response to hypoxia from the first day of life, with no postnatal maturation thereafter. In preterm lambs, HR did not change before day 14 and the full-term-like response was not acquired before 2 weeks after theoretical term. In both groups, mean arterial pressure tended to decrease below baseline, but the amplitude of variations remained of small magnitude.


CONCLUSIONS
The present results bring unique evidence that preterm birth is associated with a blunted heart response to steady-state hypoxia during the first postnatal week and a delay in the maturation of HR response.
Pladys
Patrick
P
INSERM, U642, CHU Rennes, Rennes, France.
Arsenault
Julie
J
Reix
Philippe
P
Rouillard Lafond
Joelle
J
Moreau-Bussière
François
F
Praud
Jean-Paul
JP
D000818:Animals; D000831:Animals, Newborn; D001794:Blood Pressure / Q000502:physiology*; D002319:Cardiovascular System / Q000503:physiopathology*; D004195:Disease Models, Animal; D004562:Electrocardiography; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D007231:Infant, Newborn; D007234:Infant, Premature; D012756:Sheep