Development of an isolated, pulsatile blood-perfused rat lung model for evaluating the preserved lung functions

Perfusion with lipopolysaccharide negative blood eliminates lipopolysaccharide induced lung injury

We investigated whether perfusion with control blood improves pulmonary functions compromised by lipopolysaccharide (LPS) infusion. This was an animal study in a research laboratory at a university hospital by using Sprague-Dawley rats (n = 19), each weighing 325 to 350 g. All animals were pretreated with a 24 hour infusion of either LPS (5 mg/kg) or vehicle, after which, excised lungs were reperfused for 2 hours with either LPS+ or control blood. Three groups were studied: (1) group S (n = 6); LPS pretreated lungs reperfused with LPS containing blood to mimic persistent sepsis, (2) group N (n = 6); LPS pretreated lungs reperfused with control blood to mimic the removal of the septic blood components, and (3) group C (n = 7); vehicle pretreated lungs reperfused with normal blood as a control. Blood gas exchange, shunt fraction (Qs/Qt), alveolar-arterial oxygen gradient (A-aDO2), and variables for lung mechanics were measured. Leukosequestration was quantified with a myeloperoxidase (MPO) assay. The PO2 (mm Hg) values at 90 min after reperfusion in groups S, N, and C were 67.8 +/- 7.0*, 85.2 +/- 9.2, and 90.1 +/- 7.5, respectively (*p < 0.05; vs. group N and C). In addition to PO2, A-aDO2 and Qs/Qt significantly deteriorated in group S. MPO activity in the lungs after LPS infusion was significantly higher than that after vehicle infusion (1.7 +/- 0.3 vs. 0.12 +/- 0.04 units/g tissue; p < 0.001). Subsequent reperfusion with LPS+ blood (group S) increased MPO activity to 3.1 +/- 0.6 (p < 0.05), but reperfusion with normal blood (group N) caused a significant decrease to 1.1 +/- 0.2 (p < 0.05). MPO activity in group C did not significantly change compared with those after vehicle infusion. Reperfusion with control blood normalized lung function compromised by pretreatment with LPS and significantly reduced leukosequestration. These results favor the possibility that the removal of LPS+ blood components may eliminate septic lung injury.

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.

Calcium channel blocker enhances lung preservation

BACKGROUND

The standard program for lung transplantation employs PGE1 pretreatment for donor lungs, but its efficacy remains controversial. Calcium channel blocker has been reported more effective for reducing potassium-induced vasoconstriction. We investigate the efficacy of calcium channel blocker in the initial lung flush using rat lung transplant model.

METHODS

The excised rat lungs (n = 30) were flushed with either University of Wisconsin solution (UWS) with a prior injection of 50 microg/kg PGE1 into the pulmonary artery (UWS + PGE1; n = 7), UWS only (UWS; n = 7), or UWS containing 10(-6) M nifedipine (UWS + Nif; n = 8). After storage (4 degrees C) for 24 hours, all lungs were reperfused for 2 hours using an isolated, pulsatile blood perfused lung model. Control lungs (n = 8) were reperfused immediately after harvest. Blood gas analysis and shunt fraction, lung airway resistance, dynamic lung compliance, and pulmonary vascular resistance were assessed.

RESULTS

The pO2 at 30 minutes after reperfusion in the control, UWS, UWS + PGE1, and UWS + Nif group were 88.0 +/- 3.2, 49.6 +/- 2.2, 52.0 +/- 2.4, 85.1 +/- 2.1 (mmHg), respectively. Until 30 minutes after reperfusion, the pO2 in UWS and UWS + PGE1 group were significantly lower than those in UWS + Nif group (p < .001). Shunt fraction, lung airway resistance, and dynamic lung compliance also demonstrated the superiority of UWS + Nif group.

CONCLUSIONS

The early graft function after storage was significantly enhanced in lungs flushed with UWS containing nifedipine. Calcium channel blocker is more effective than PGE1 in reducing the potassium-induced vasoconstriction. Optimal composition of the flush may require both calcium channel blocker for pulmonary vasodilation and PGE1 for pulmonary protection by non-vasodilatory mechanisms.