Reliable 18-hour lung preservation with University of Wisconsin solution. An ex vivo rat model with a pulsatile perfusion system.

OBJECTIVES: A common experimental model is necessary to assess therapeutic intervention in lung preservation. This study was designed to establish lung preservation in an ex vivo rat model that would enable post-storage lung function to be stably evaluated during the 2 hours following reperfusion. SUBJECTS AND METHODS: Lungs isolated from Sprague-Dawley rats (n = 36) were flushed and stored in University of Wisconsin solution at 4 degrees C for the following periods: Group 1: no storage (n = 12); Group 2: 4 hours (n = 8); Group 3: 18 hours (n = 8); and Group 4: 24 hours (n = 8). After storage in University of Wisconsin solution, all lungs were reperfused with homologous venous blood exsanguinated from donor rats using a pulsatile perfusion system. Pulmonary variables, including lung airway resistance, dynamic lung compliance, total pulmonary vascular resistance, and blood gas analysis, were assessed during reperfusion.
RESULTS: All lungs stored for 24 hours failed within 1 hour of reperfusion. Lungs stored for up to 18 hours survived 2-hour reperfusion. pO2 in groups 1 to 3 (87.1 +/- 3.5, 89.7 +/- 2.4, and 80.6 +/- 6.4, pO2 mmHg at 30 minutes) was similar during reperfusion, but that in group 4 (49.5 +/- 4.6 mmHg, at 30 minutes) deteriorated within 30 minutes after reperfusion onset. Lung airway resistance, dynamic lung compliance, and shunt fraction also deteriorated in group 4, whereas these variables were similar in groups 1, 2, and 3 during reperfusion.
CONCLUSIONS: These results indicate that this experimental model provided a reliable evaluation of preserved lung function after 18-hour cold storage. Any therapeutic intervention for extending storage periods or ameliorating post-storage lung function is easily tested using this system.