Abstract
Tolerance of hypoxia differs among species and with age. Within age groups there is considerable individual variation which is as yet poorly understood.In response to hypoxemia cardio-circulatory adaptation plays a central role. We studied the changes of cardiac performance in artificially ventilated piglets aging 8 to 42 hours (n=10) under fluothane-N2O-O2-anaesthesia. After a stable control period arterial Po2 was lowered from 60-90 mmHg to 30-40 mmHg (hemoglobine-oxygen-saturation 70-90%) by lowering FiO2 at otherwise constant conditions.
Mean heart rate rose continuously by + 38% at 111± 85 min hypoxia time (p 0,001).However,cardiac output, stroke volume,cardiac power, mean aortic blood pressure, aortic peak flow reached their maxima (+11 to +32%;p 0,01),and vascular resistance its minimum (−17%; p 0,01) already during the first 30 min. They subsequently fell below (−60 to −90%) or surmounted (+45%) control levels.These changes were accompanied by increasing metabolic acidosis.Average survival time was 188± 98 min. Survival time depended exclusively on the animal's ability to increase its heart rate (K=0,83).It was shorter in piglets who started with heart rates above the average control level (133± 61 min)than those with heart rates below it (227± 104 min).
It is to be concluded that newborn piglets are unable to compensate sustained hypoxemia of such degree by means of cardiac performance longer than 30 min.
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Angerpointner, T., Linderkamp, O., Stallinger, H. et al. The effect of hypoxia on cardiac performance in newborn piglets-evaluation by the electromagnetic method: 22. Pediatr Res 14, 169 (1980). https://doi.org/10.1203/00006450-198002000-00049
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DOI: https://doi.org/10.1203/00006450-198002000-00049