Restoration of cardiopulmonary function with 21% versus 100% oxygen after hypoxaemia in newborn pigs

• Published in: Archives of disease in childhood. Fetal and neonatal edition Vol. 90; no. 3; pp. F229 - f234
• Main Authors: Fugelseth, D, Børke, W B, Lenes, K, Matthews, I, Saugstad, O D, Thaulow, E
• Format: Journal Article
• Language: English
• Published: England BMJ Publishing Group Ltd and Royal College of Paediatrics and Child Health 01-05-2005; BMJ Publishing Group LTD; BMJ Group
• Subjects: Animals; Animals, Newborn; Asphyxia Neonatorum - blood; Asphyxia Neonatorum - physiopathology; Asphyxia Neonatorum - therapy; Biomarkers - blood; Blood Pressure; Body weight; Cardiac arrhythmia; Cardiac Output; cardiac troponin I; cTnI; Disease Models, Animal; Experiments; Heart Rate; Humans; Hypoxia; Hypoxia - blood; Hypoxia - physiopathology; Hypoxia - therapy; Infant, Newborn; left ventricular pressure; LVP; Original; Oxygen; Oxygen Inhalation Therapy - methods; PAP; peak tricuspid regurgitation velocity; pig; Pulmonary arteries; Pulmonary Artery - diagnostic imaging; Pulmonary Artery - physiopathology; pulmonary artery pressure; pulmonary hypertension; resuscitation; Resuscitation - methods; Swine; TR-Vmax; Troponin I - blood; Ultrasonography; Veins & arteries; Ventilation
• ISSN: 1359-2998; 1468-2052
• DOI: 10.1136/adc.2004.056986

Objective: To assess the consequences of hypoxaemia and resuscitation with room air versus 100% O2 on cardiac troponin I (cTnI), cardiac output (CO), and pulmonary artery pressure (PAP) in newborn pigs. Design: Twenty anaesthetised pigs (12–36 hours; 1.7–2.7 kg) were subjected to hypoxaemia by ventilation with 8% O2. When mean arterial blood pressure fell to 15 mm Hg, or arterial base excess was ⩽ −20 mmol/l, resuscitation was performed with 21% (n  =  10) or 100% (n  =  10) O2 for 30 minutes, then ventilation with 21% O2 for 120 minutes. Blood was analysed for cTnI. Ultrasound examinations of CO and PAP (estimated from tricuspid regurgitation velocity (TR-Vmax)) were performed at baseline, during hypoxia, and at the start of and during reoxygenation. Results: cTnI increased from baseline to the end point (p<0.001), confirming a serious myocardial injury, with no differences between the 21% and 100% O2 group (p  =  0.12). TR-Vmax increased during the insult and returned towards baseline values during reoxygenation, with no differences between the groups (p  =  0.11) or between cTnI concentrations (p  =  0.31). An inverse relation was found between increasing age and TR-Vmax during hypoxaemia (p  =  0.034). CO per kg body weight increased during the early phase of hypoxaemia (p<0.001), then decreased. Changes in CO per kg were mainly due to changes in heart rate, with no differences between the groups during reoxygenation (p  =  0.298). Conclusion: Hypoxaemia affects the myocardium and PAP. During this limited period of observation, reoxygenation with 100% O2 showed no benefits compared with 21% O2 in normalising myocardial function and PAP. The important issue may be resuscitation and reoxygenation without hyperoxygenation.