Influence of Prematurity on Postnatal Maturation of Heart Rate and Arterial Pressure Responses to Hypoxia in Lambs

Abstract

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. Objectives: 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 (FIO₂ = 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. Conclusion: 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.

Effects of preterm birth and ventilation on glomerular capillary growth in the neonatal lamb kidney

“…A disadvantage of this study is that the physiological measures were not comparatively assessed in term control animals. Previous studies, however, in term and preterm lambs within the first 3–4 days of life show that all were within the expected range [18, 19, 28, 29]. …”

MRI Techniques and New Animal Models for Imaging the Brain

“…Large animals are commonly used as experimental models for human-infant research into brain disorders (pig, Lind et al 2007), sudden infant death syndrome (pig, Tong et al 1995), head injury (Lehman et al 2002), brain injury induced by hypoxia (pig, Foster et al 2001; www.intechopen.com sheep, Laurini et al 1999) or by preterm birth (sheep, Patural et al 2010, Pladys et al 2008, Riddle et al 2006, and neurobehavioural topics (pig, Friess et al 2007). They can also be used for xenografts in Parkinson's disease (Molenaar et al 1997).…”

The normal electrocardiograms in the conscious newborn lambs in neonatal period and its progression

“…The cardiac physiology of lambs at birth differs to that of adults, with the electrocardiographic tracing of neonates being influenced by various parameters. Examples include blood pressure [ 5 – 7 ], peripheral vascular resistance [ 6 ], cardiac output [ 8 ], the relationship between the right and left ventricular masses [ 9 , 10 ], anatomical conformation [ 11 , 12 ], and autonomic innervations [ 7 , 13 – 15 ]. Most electrocardiographic studies of sheep have been conducted on adult animals or fetuses, with descriptions about neonates remaining limited in the published literature [ 15 ].…”