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Resuscitation with 100% O₂ does not protect the myocardium in hypoxic newborn piglets

¹ Department of Pediatric Research, Rikshospitalet University Hospital, Oslo, Norway
² Department of Pediatrics
³ Institute for Surgical Research
⁴ Department of Clinical Chemistry, Rikshospitalet
⁵ Department of Anaesthesiology, Aker University Hospital, Oslo

Correspondence to:
Correspondence to:
Dr Børke
Rikshospitalet, Oslo 0027, Norway; w.b.borke{at}klinmed.uio.no

Background: Perinatal asphyxia is associated with cardiac dysfunction secondary to myocardial ischaemia. Cardiac troponin I (cTnI) is a marker of myocardial necrosis. Raised concentrations in the blood are related to perinatal asphyxia and increased morbidity.

Objective: To assess porcine myocardial damage from enzyme release during hypoxaemia induced global ischaemia, and subsequent resuscitation with ambient air or 100% O₂. To investigate whether CO₂ level during resuscitation influences myocardial damage.

Design: Newborn piglets (12–36 hours) were exposed to hypoxaemia by ventilation with 8% O₂ in nitrogen. When mean arterial blood pressure had fallen to 15 mm Hg, or base excess to < -20 mmol/l, the animals were randomly resuscitated by ventilation with either 21% O₂ (group A, n = 29) or 100% O₂ (group B, n = 29) for 30 minutes. Afterwards they were observed in ambient air for another 150 minutes. During resuscitation, the two groups were further divided into three subgroups with different CO₂ levels.

Analysis: Blood samples were analysed for cTnI, myoglobin, and creatine kinase-myocardial band (CK-MB) at baseline and at the end of the study.

Results: cTnI increased more than 10-fold (p < 0.001) in all the groups. Myoglobin and CK-MB doubled in concentration.

Conclusion: The considerable increase in cTnI indicates seriously affected myocardium. Reoxygenation with 100% oxygen offered no biochemical benefit over ambient air. CK-MB and myoglobin were not reliable markers of myocardial damage. Normoventilation tended to produce better myocardial outcome than hyperventilation or hypoventilation.

Keywords: troponin I; myocardium; heart; pig; resuscitation

Abbreviations: cTnI, cardiac troponin I; PAP, pulmonary artery pressure; PIP, peak inspiratory pressure; PVR, pulmonary vascular resistance

This article has been cited by other articles:

				T H M Fenton Asphyxia or just hypoxia? Arch. Dis. Child. Fetal Neonatal Ed., May 1, 2006; 91(3): F234 - F234. [Full Text] [PDF]

				D Fugelseth, W B Borke, K Lenes, I Matthews, O D Saugstad, and E Thaulow Restoration of cardiopulmonary function with 21% versus 100% oxygen after hypoxaemia in newborn pigs Arch. Dis. Child. Fetal Neonatal Ed., May 1, 2005; 90(3): F229 - f234. [Abstract] [Full Text] [PDF]

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