Lung protection in cardio-pulmonary bypass.

Since the invention of the heart-lung machine paediatric cardiac surgery developed rapidly. For correction of complex cardiac malformations the application of a cardio-pulmonary bypass (CPB) has become indispensable but possible negative effects of this technique should not be neglected. Especially, both bypassed organs i.e. heart and lung are not perfused during the procedure and therefore are threatened by ischemia and reperfusion injury. Additionally, CPB was developed with a non-pulsatile flow but there are clinical observations that pulsatile flow might be superior with improved patient outcomes. Thus, the aim of our study was to evaluate the effect of CPB on lung structure and to assess whether different flow modalities (pulsatile vs. non-pulsatile flow) or application of the antibiotic minocycline might be advantageous. Thirty five piglets of four weeks age were examined and divided into five experimental groups: control (no CPB) without or with minocycline, CPB (non-pulsatile flow) without or with minocycline and CPB with pulsatile flow. CPB was performed for 90 min followed by a 120 min reperfusion and recovery phase. Thereafter, adenosine triphosphate-content of lung biopsies and histology was carried out. We found that CPB was associated with a significant thickening of alveolar wall accompanied by an infiltration of neutrophil leucocytes. Moreover, markers for hypoxia, apoptosis, nitrosative stress, inflammation and DNA damage were significantly elevated after CPB. These cellular damages could be partially inhibited by minocycline or pulsatile flow. Both, minocycline and pulsatile flow attenuate lung damage after CPB.

[Influence of ECMO and IABP on coronary blood flow. Valuable combination or waste of resources?]. / Einfluss von ECMO und IABP auf die Koronardurchblutung. Sinnvolle Kombination oder Ressourcenverschwendung?

BACKGROUND: The treatment of patients in severe cardiogenic shock with an intra-aortic balloon pump (IABP) or extracorporeal membrane oxygenation (ECMO) is a common procedure to achieve stabilization. Only limited data are available on the simultaneous use of both systems. The aim of the present study was to assess the effect of the concomitant use of IABP and ECMO on coronary blood flow. In addition, the influence of antegrade and retrograde perfusion was evaluated. METHODS: A median sternotomy was performed in adult pigs under general anesthesia. Arterial ECMO perfusion was realized through the ascending aorta or the femoral artery, and the IABP was implanted via the second femoral artery. Six measurements of arterial pressure in the left anterior descending artery (LAD) and in the left atrium were made at intervals of 2 min. In addition, lactate concentration and oxygen saturation in the coronary sinus were recorded. The ECMO support was either 100 or 50 % of cardiac output. Each experiment was carried out first without and then with additional IABP support. RESULTS: The simultaneous use of ECMO and IABP is feasible for antegrade perfusion, where the IABP leads to an increase of blood pressure in the coronary arteries. In addition, the myocardial oxygen supply improves. By contrast, the use of an IABP in retrograde perfusion leads to a reduction of blood pressure in the LAD and to a reduced oxygen supply. A comparison between antegrade and retrograde perfusion with IABP support showed significantly better mean arterial pressure in the LAD for antegrade perfusion. Without IABP, blood pressure in the LAD was better in retrograde perfusion. CONCLUSION: In antegrade perfusion the simultaneous use of IABP and ECMO is useful. In retrograde perfusion IABP impairs the mean arterial pressure and consequently the perfusion of the coronary arteries.

Pre-ischaemic exogenous surfactant reduces pulmonary injury in rat ischaemia/reperfusion.

The optimal timing of exogenous surfactant application to reduce pulmonary injury and dysfunction was investigated in a rat lung ischaemia and reperfusion injury model. Lungs were subjected to flush perfusion, surfactant instillation, cold ischaemia (4 degrees C, 4 h) and reperfusion (60 min). Animals received surfactant before (group 1) or at the end (2) of ischaemia, or during reperfusion (3) or not at all (4). Control groups included "worst case" without Perfadex and surfactant (5), "no injury" without (6) or with surfactant (7), and ischaemia with pre-ischaemic surfactant (8). Intra-alveolar oedema and blood-air barrier injury were estimated by light and electron microscopic stereology. Perfusate oxygenation and pulmonary arterial pressure (P(pa)) were determined during reperfusion in groups 1 to 4. Intra-alveolar oedema was almost absent in groups 1, 6, 7 and 8, pronounced in 2, 3 and 4, and severe in 5. Blood-air barrier injury was moderate in groups 1 and 8, slightly pronounced in 2, 3 and 4, extensive in 5 and almost absent in 6 and 7. Perfusate oxygenation was significantly higher in group 1 compared with groups 2 to 4. P(pa) did not differ between the groups. In conclusion, exogenous surfactant attenuates intra-alveolar oedema formation and blood-air barrier damage and improves perfusate oxygenation in the rat lung, especially when applied before ischaemic storage.