Ex vivo rehabilitation of non-heart-beating donor lungs in preclinical porcine model: delayed perfusion results in superior lung function

Abstract

Objectives: Ex vivo lung perfusion (EVLP) is a promising modality for the evaluation and treatment of marginal donor lungs. The optimal timing of EVLP initiation and the potential for rehabilitation of donor lungs with extended warm ischemic times is unknown. The present study compared the efficacy of different treatment strategies for uncontrolled non-heart-beating donor lungs.

Methods: Mature swine underwent hypoxic arrest, followed by 60 minutes of no-touch warm ischemia. The lungs were harvested and flushed with 4°C Perfadex. Three groups (n = 5/group) were stratified according to the preservation method: cold static preservation (CSP; 4 hours of 4°C storage), immediate EVLP (I-EVLP: 4 hours EVLP at 37°C), and delayed EVLP (D-EVLP; 4 hours of CSP followed by 4 hours of EVLP). The EVLP groups were perfused with Steen solution supplemented with heparin, methylprednisolone, cefazolin, and an adenosine 2A receptor agonist. The lungs then underwent allotransplantation and 4 hours of recipient reperfusion before allograft assessment for resultant ischemia-reperfusion injury.

Results: The donor blood oxygenation (partial pressure of oxygen/fraction of inspired oxygen ratio) before death was not different between the groups. The oxygenation after transplantation was significantly greater in the D-EVLP group than in the I-EVLP or CSP groups. The mean airway pressure, pulmonary artery pressure, and expression of interleukin-8, interleukin-1β, and tumor necrosis factor-α were all significantly reduced in the D-EVLP group. Post-transplant oxygenation exceeded the acceptable clinical levels only in the D-EVLP group.

Conclusions: Uncontrolled non-heart-beating donor lungs with extended warm ischemia can be reconditioned for successful transplantation. The combination of CSP and EVLP in the D-EVLP group was necessary to obtain optimal post-transplant function. This finding, if confirmed clinically, will allow expanded use of nonheart-beating donor lungs.

Figure 1

Non-heart-beating donor lung harvest and ex vivo lung perfusion (EVLP) procedures. A. Fresh clot being removed from the donor left atrium and pulmonary veins during the antegrade lung flush. B. Donor lungs pictured during EVLP with the pulmonary artery cannula, left atrial cannula, and endotracheal tube secured in place.

Figure 2

Lung physiology after 4 hours of reperfusion. A. Mean airway pressure (mmHg). B. Mean pulmonary artery (PA) pressure (mmHg). C. Oxygenation as represented by the ratio of partial pressure of oxygen to fraction of inspired oxygen (PO₂:FiO₂) measured at four time points: donor arterial blood oxygenation prior to euthanasia, EVLP-perfusate oxygenation at one hour, EVLP-perfusate oxygenation at four hours, and recipient arterial blood oxygenation at the end of transplantation. Groups: cold-static preservation (CSP), immediate ex vivo lung perfusion (I-EVLP), and delayed ex vivo lung perfusion (D-EVLP). A., B.: *p < 0.05 vs. CSP, #p < 0.05 vs. CSP and I-EVLP. C.: *p < 0.05 vs. I-EVLP, #p < 0.05 vs. CSP and I-EVLP.

Figure 3

Mean proinflammatory cytokine levels (pg/mL) in bronchoalveolar lavage fluid at the end of 4 hours of reperfusion. Groups: cold-static preservation (CSP), immediate ex vivo lung perfusion (I-EVLP), and delayed ex vivo lung perfusion (D-EVLP). *p < 0.05 vs. CSP. #p < 0.05 vs. CSP and I-EVLP.

Figure 4

Representative histologic (top, hematoxylin-eosin sections, 20X) and gross (bottom) appearance of lungs after 4 hours of reperfusion. Groups: cold-static preservation (CSP), immediate ex vivo lung perfusion (I-EVLP), and delayed ex vivo lung perfusion (D-EVLP).

Figure 5

Mean lung injury severity scores by histology. A score on a scale of 0–3 was assigned for each section: neutrophils per high powered field (score: 0=<5, 1=6–10, 2=11–20, 3=>20), alveolar edema (score: 0=<5%, 1=6–25%, 2=26=50%, 3=>50%), interstitial infiltration (score: 0=none, 1=minimal, 2=moderate, 3=severe), and a composite score obtained by summation of these three criteria (0–9). Groups: cold-static preservation (CSP), immediate ex vivo lung perfusion (I-EVLP), and delayed ex vivo lung perfusion (D-EVLP). *p < 0.05 vs. CSP. #p < 0.05 vs. I-EVLP.