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Circulatory responses to asphyxia differ if the asphyxia occurs in utero or ex utero in near-term lambs.

Sobotka KS, Morley C, Ong T, Polglase GR, Aridas JD, Miller SL, Schmölzer GM, Klingenberg C, Moss TJ, Jenkin G, Hooper SB - PLoS ONE (2014)

Bottom Line: Mean arterial pressure initially increased then decreased in both groups.This indicates that the cardiovascular responses to perinatal asphyxia are significantly influenced by the newborn's local environment.As such, based solely on heart rate, the stage and severity of a perinatal asphyxic event may not be as accurate as previously assumed.

View Article: PubMed Central - PubMed

Affiliation: The Ritchie Centre, Monash University, Melbourne, Australia.

ABSTRACT

Background: A cornerstone of neonatal resuscitation teaching suggests that a rapid vagal-mediated bradycardia is one of the first signs of perinatal compromise. As this understanding is based primarily on fetal studies, we investigated whether the heart rate and blood pressure response to total asphyxia is influenced by whether the animal is in utero or ex utero.

Methods: Fetal sheep were instrumented at ∼ 139 days of gestation and then asphyxiated by umbilical cord occlusion until mean arterial blood pressure decreased to ∼ 20 mmHg. Lambs were either completely submerged in amniotic fluid (in utero; n = 8) throughout the asphyxia or were delivered and then remained ex utero (ex utero; n = 8) throughout the asphyxia. Heart rate and arterial blood pressure were continuously recorded.

Results: Heart rate was higher in ex utero lambs than in utero lambs. Heart rates in in utero lambs rapidly decreased, while heart rates in ex utero lambs initially increased following cord occlusion (for ∼ 1.5 min) before they started to decrease. Mean arterial pressure initially increased then decreased in both groups.

Conclusions: Heart rate response to asphyxia was markedly different depending upon whether the lamb was in utero or ex utero. This indicates that the cardiovascular responses to perinatal asphyxia are significantly influenced by the newborn's local environment. As such, based solely on heart rate, the stage and severity of a perinatal asphyxic event may not be as accurate as previously assumed.

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Mean blood pressure (BP), expressed as a percentage change from before cord clamping measured in in utero (•) or ex utero (○) lambs before and after umbilical cord occlusion (designated as time 0).Data are mean ± SEM. * p<0.05 in utero vs ex utero.
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pone-0112264-g002: Mean blood pressure (BP), expressed as a percentage change from before cord clamping measured in in utero (•) or ex utero (○) lambs before and after umbilical cord occlusion (designated as time 0).Data are mean ± SEM. * p<0.05 in utero vs ex utero.

Mentions: HR in ex utero lambs was significantly higher than in utero lambs for the first 10 min of asphyxia. Almost immediately following umbilical cord occlusion, HR in in utero lambs rapidly decreased, resulting in a ∼50% reduction within 2 min (Figure 1). In contrast, HR in ex utero lambs initially increased following cord occlusion (for ∼1.5 min) by ∼15% before they started to decrease; at 2 min they were not different from before cord occlusion. Mean BP initially increased then decreased in both groups. BP was higher in ex utero lambs from 6.5 to 10 min after asphyxia onset (Figure 2).


Circulatory responses to asphyxia differ if the asphyxia occurs in utero or ex utero in near-term lambs.

Sobotka KS, Morley C, Ong T, Polglase GR, Aridas JD, Miller SL, Schmölzer GM, Klingenberg C, Moss TJ, Jenkin G, Hooper SB - PLoS ONE (2014)

Mean blood pressure (BP), expressed as a percentage change from before cord clamping measured in in utero (•) or ex utero (○) lambs before and after umbilical cord occlusion (designated as time 0).Data are mean ± SEM. * p<0.05 in utero vs ex utero.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4230987&req=5

pone-0112264-g002: Mean blood pressure (BP), expressed as a percentage change from before cord clamping measured in in utero (•) or ex utero (○) lambs before and after umbilical cord occlusion (designated as time 0).Data are mean ± SEM. * p<0.05 in utero vs ex utero.
Mentions: HR in ex utero lambs was significantly higher than in utero lambs for the first 10 min of asphyxia. Almost immediately following umbilical cord occlusion, HR in in utero lambs rapidly decreased, resulting in a ∼50% reduction within 2 min (Figure 1). In contrast, HR in ex utero lambs initially increased following cord occlusion (for ∼1.5 min) by ∼15% before they started to decrease; at 2 min they were not different from before cord occlusion. Mean BP initially increased then decreased in both groups. BP was higher in ex utero lambs from 6.5 to 10 min after asphyxia onset (Figure 2).

Bottom Line: Mean arterial pressure initially increased then decreased in both groups.This indicates that the cardiovascular responses to perinatal asphyxia are significantly influenced by the newborn's local environment.As such, based solely on heart rate, the stage and severity of a perinatal asphyxic event may not be as accurate as previously assumed.

View Article: PubMed Central - PubMed

Affiliation: The Ritchie Centre, Monash University, Melbourne, Australia.

ABSTRACT

Background: A cornerstone of neonatal resuscitation teaching suggests that a rapid vagal-mediated bradycardia is one of the first signs of perinatal compromise. As this understanding is based primarily on fetal studies, we investigated whether the heart rate and blood pressure response to total asphyxia is influenced by whether the animal is in utero or ex utero.

Methods: Fetal sheep were instrumented at ∼ 139 days of gestation and then asphyxiated by umbilical cord occlusion until mean arterial blood pressure decreased to ∼ 20 mmHg. Lambs were either completely submerged in amniotic fluid (in utero; n = 8) throughout the asphyxia or were delivered and then remained ex utero (ex utero; n = 8) throughout the asphyxia. Heart rate and arterial blood pressure were continuously recorded.

Results: Heart rate was higher in ex utero lambs than in utero lambs. Heart rates in in utero lambs rapidly decreased, while heart rates in ex utero lambs initially increased following cord occlusion (for ∼ 1.5 min) before they started to decrease. Mean arterial pressure initially increased then decreased in both groups.

Conclusions: Heart rate response to asphyxia was markedly different depending upon whether the lamb was in utero or ex utero. This indicates that the cardiovascular responses to perinatal asphyxia are significantly influenced by the newborn's local environment. As such, based solely on heart rate, the stage and severity of a perinatal asphyxic event may not be as accurate as previously assumed.

Show MeSH
Related in: MedlinePlus