Pulmonary Circulation and Plasma-Endothelin-1 (P-Et-1) During Hypoxia and Reoxygenation With 21% and 100% O₂ in Piglets

Background: We tested the hypothesis that room air normalises pulmonary arterial pressure (PAP) and pulmonary vascular resistance index(PVRI) during reoxygenation as efficient as 100% O₂ in hypoxic piglets .Subjects: Eighteen 1-3 d old piglets. Intervention: Hypoxia was induced by ventilation with 8% O₂. When mean arterial blood pressure fell below 20 mm Hg or base excess was reduced to <-20 mmol/L a 2-hour reoxygenation-period was started, the piglets were randomly divided into 2 groups; 21% O₂ (group 1, n=9) and 100% O₂ (group 2, n=9).Results: P-ET-1 decreased during hypoxia from 1.53 ±0.51 ng/L(mean±SD) to 1.17 ±0.55 ng/L (p=0.011) in both groups. At 2 h reoxygenation P-ET-1 increased to 1.92 ±0.90 ng/L (p=0.017) in group 1, and to 1.67 ±0.61 ng/L (p=0.002) in group 2. PAP increased from 24±6 mm Hg at start to 35 ±9 mm Hg at 5 min. reoxygenation in group 1 (p=0.01), and from 27 ±8 mmHg to 31 ±6 (N.S.) in group 2. PVRI decreased from the start of reoxygenation from 0.42 ±0.25 to to 0.15 ±0.11 (p=0.011) and from 0.54 ±0.50 to 0.23 ±0.13(N.S) at 20 min reoxygenation in group 1 and 2, respectively .Conclusion: During reoxygenation PVRI is reduced just as efficient with 21% as 100% O₂, an the changes in P-ET-1 are comparable to the changes PVRI, suggesting that changes in PVRI may be mediated by P-ET-1.