Restoration of cardiopulmonary function with 21% versus 100% oxygen after hypoxaemia in newborn pigs.
OBJECTIVE
To assess the consequences of hypoxaemia and resuscitation with room air versus 100% O(2) on cardiac troponin I (cTnI), cardiac output (CO), and pulmonary artery pressure (PAP) in newborn pigs.


METHODS
Twenty anaesthetised pigs (12-36 hours; 1.7-2.7 kg) were subjected to hypoxaemia by ventilation with 8% O(2). When mean arterial blood pressure fell to 15 mm Hg, or arterial base excess was < or = -20 mmol/l, resuscitation was performed with 21% (n = 10) or 100% (n = 10) O(2) for 30 minutes, then ventilation with 21% O(2) 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% O(2) 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).


CONCLUSIONS
Hypoxaemia affects the myocardium and PAP. During this limited period of observation, reoxygenation with 100% O(2) showed no benefits compared with 21% O(2) in normalising myocardial function and PAP. The important issue may be resuscitation and reoxygenation without hyperoxygenation.
Fugelseth
D
D
Department of Paediatric Research, Rikshospitalet University Hospital, Oslo, Norway. drfu@uus.no
Børke
W B
WB
Lenes
K
K
Matthews
I
I
Saugstad
O D
OD
Thaulow
E
E
D000818:Animals; D000831:Animals, Newborn; D001238:Asphyxia Neonatorum / Q000097:blood / Q000503:physiopathology / Q000628:therapy*; D015415:Biomarkers / Q000097:blood; D001794:Blood Pressure; D002302:Cardiac Output; D004195:Disease Models, Animal; D006339:Heart Rate; D006801:Humans; D000860:Hypoxia / Q000097:blood / Q000503:physiopathology / Q000628:therapy*; D007231:Infant, Newborn; D010102:Oxygen Inhalation Therapy / Q000379:methods*; D011651:Pulmonary Artery / Q000000981:diagnostic imaging / Q000503:physiopathology; D012151:Resuscitation / Q000379:methods; D013552:Swine; D019210:Troponin I / Q000097:blood; D014463:Ultrasonography
D015415:Biomarkers; D019210:Troponin I