A typical complications after cardiac surgery is that patients leave the operating theatre with good blood gas values, but develop respiratory clinical problems within 24h. We investigated whether extracorporeal circulation may induce early biochemical and histological changes in the lungs preceding this development. Anaesthetized piglets (n=9) underwent extracorporeal circulation with hypothermic (25UC) cardioplegic arrest for 90min followed by 3h reperfusion. Another group additionally received a PARP- Inhibitor (INO1001 1 mg/kg/h; n=19)in comparison to normal and sham-operated piglets(n=11). In the lungs we found that type I alveocytes exhibited significant swelling, interstitial oedema, intra-alveolar erythrocyte and granulocyte accumulation, as well as fibrinous exudates. There was significant up-regulation of TNFa and of heat shock protein HSP70 as compared to control piglets. PARP-Inhibitor group significantly prevented from TNFa, HSP70 and alveocyte thickening. Despite these dramatic changes, blood gases were -as expected from the clinical situation-

only slightly affected at that early point in time. In conclusion: The observed changes correspond to an early stage of a shock lung with ?at that time- still sufficient gas transport.