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

Kristina Sobotka, Colin J Morley, Tracey Ong, Graeme Polglase, James Aridas, Suzanne Lee Miller, Georg Marcus Schmolzer, Claus Klingenberg, Timothy James Murugesan Moss, Graham Jenkin, Stuart Brian Hooper

Research output: Contribution to journalArticleResearchpeer-review

Abstract

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 approximately 139 days of gestation and then asphyxiated by umbilical cord occlusion until mean arterial blood pressure decreased to approximately 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 approximately 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.
Original languageEnglish
Pages (from-to)1 - 5
Number of pages5
JournalPLoS ONE
Volume9
Issue number11 (Art. ID: e112264)
DOIs
Publication statusPublished - 2014

Cite this

Sobotka, Kristina ; Morley, Colin J ; Ong, Tracey ; Polglase, Graeme ; Aridas, James ; Miller, Suzanne Lee ; Schmolzer, Georg Marcus ; Klingenberg, Claus ; Moss, Timothy James Murugesan ; Jenkin, Graham ; Hooper, Stuart Brian. / Circulatory responses to asphyxia differ if the asphyxia occurs in utero or ex utero in near-term lambs. In: PLoS ONE. 2014 ; Vol. 9, No. 11 (Art. ID: e112264). pp. 1 - 5.
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title = "Circulatory responses to asphyxia differ if the asphyxia occurs in utero or ex utero in near-term lambs",
abstract = "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 approximately 139 days of gestation and then asphyxiated by umbilical cord occlusion until mean arterial blood pressure decreased to approximately 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 approximately 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.",
author = "Kristina Sobotka and Morley, {Colin J} and Tracey Ong and Graeme Polglase and James Aridas and Miller, {Suzanne Lee} and Schmolzer, {Georg Marcus} and Claus Klingenberg and Moss, {Timothy James Murugesan} and Graham Jenkin and Hooper, {Stuart Brian}",
year = "2014",
doi = "10.1371/journal.pone.0112264",
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Circulatory responses to asphyxia differ if the asphyxia occurs in utero or ex utero in near-term lambs. / Sobotka, Kristina; Morley, Colin J; Ong, Tracey; Polglase, Graeme; Aridas, James; Miller, Suzanne Lee; Schmolzer, Georg Marcus; Klingenberg, Claus; Moss, Timothy James Murugesan; Jenkin, Graham; Hooper, Stuart Brian.

In: PLoS ONE, Vol. 9, No. 11 (Art. ID: e112264), 2014, p. 1 - 5.

Research output: Contribution to journalArticleResearchpeer-review

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T1 - Circulatory responses to asphyxia differ if the asphyxia occurs in utero or ex utero in near-term lambs

AU - Sobotka, Kristina

AU - Morley, Colin J

AU - Ong, Tracey

AU - Polglase, Graeme

AU - Aridas, James

AU - Miller, Suzanne Lee

AU - Schmolzer, Georg Marcus

AU - Klingenberg, Claus

AU - Moss, Timothy James Murugesan

AU - Jenkin, Graham

AU - Hooper, Stuart Brian

PY - 2014

Y1 - 2014

N2 - 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 approximately 139 days of gestation and then asphyxiated by umbilical cord occlusion until mean arterial blood pressure decreased to approximately 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 approximately 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.

AB - 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 approximately 139 days of gestation and then asphyxiated by umbilical cord occlusion until mean arterial blood pressure decreased to approximately 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 approximately 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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