Influence of Red Blood Cells on Lung Function in an ex Vivo Rat Heart-Lung Model

Crystalloid perfusates commonly are utilized for lung preservation in extracorporeal small animal lung models. However, the function of these grafts is limited. In a new ex-vivo rat heart-lung model the role of red blood cells added to the crystalloid perfusate was investigated. Heart-lung blocks were rapidly excised (n = 9, each group) and the blocks were connected to the extracorporeal perfusion circuit using Krebs-Henseleit solution (KH) or KH with washed bovine red blood cells (hematocrit 38%) (KHRBC). The lungs were ventilated with room air. The coronary system was perfused via the aortic root with oxygenated perfusate. The lungs were perfused via the right ventricle with deoxygenated perfusate (PO2 15 mm Hg). Venoarterial improvement of oxygenation, pulmonary vascular resistance (PVR), and peak inspiratory pressure (PIP) were continuously monitored for 50 min. At the end of the experiment the wet/dry (W/D) ratio was determined using the mediastinal lung lobe while the remaining lung was used for light microscopic (LM) evaluation. After 30 min of perfusion, lung function was significantly better in the KHRBC group (PVR (KH): 752 ± 193 dyn*sec*cm-5; (KHRBC): 279 ± 48 dyn*sec*cm-5; PIP (KH): 31 ± 3.2 mm Hg; (KHRBC): 25.8 ± 1.9 mm Hg). In addition, lungs perfused with KHRBC showed significantly less edema than those perfused with KH only (W/D ratio (KH): 7.8 ± 1.2; (KHRBC) 5.1 ± 0.6; LM (KH): 3.5 ± 0.9; (KHRBC): 2.3 ± 0.8). The use of red blood cells in KH perfusate improved functional and structural integrity. This resulted in prolonged observation time and enhanced validity of this newly developed ex-vivo small animal heart-lung model for various purposes.