Donation After Circulatory Death Lungs Transplantable Up to Six Hours After Ex Vivo Lung Perfusion

Abstract

Background: Despite the critical need for donor lungs, logistic and geographic barriers hinder lung utilization. We hypothesized that lungs donated after circulatory death subjected to 6 hours of cold preservation after ex vivo lung perfusion (EVLP) would have similar outcomes after transplantation as lungs transplanted immediately after EVLP, and that both would perform superiorly compared with lungs transplanted immediately after procurement.

Methods: Donor porcine lungs were procured after circulatory death and 15 minutes of warm ischemia. Three groups (n = 5 per group) were randomized: immediate left lung transplantation (Immediate group), EVLP for 4 hours followed by transplantation (EVLP group), or EVLP for 4 hours followed by 6 hours of cold preservation followed by transplantation (EVLP+Cold group). Lungs were reperfused for 2 hours before obtaining pulmonary vein samples for partial pressure of oxygen/fraction of inspired oxygen ratio calculations, airway pressures for compliance measurements, and wet/dry weight ratios.

Results: The partial pressure of oxygen/fraction of inspired oxygen ratios in the EVLP and EVLP+Cold groups were significantly improved compared with those in the Immediate group (429.7 ± 51.8 and 436.7 ± 48.2 versus 117.4 ± 22.9 mm Hg, respectively). In addition, dynamic compliance was significantly improved in the EVLP and EVLP+Cold groups compared with immediate group (26.2 ± 4.2 and 27.9 ± 3.5 versus 11.1 ± 2.4 mL/cmH₂O, respectively). There were no differences in oxygenation capacity or dynamic compliance between the EVLP and EVLP+Cold groups. Inflammatory cytokine levels were significantly lower in the EVLP and EVLP+Cold groups.

Conclusions: Lungs donated after circulatory death can be successfully transplanted as much as 6 hours after EVLP. Cold preservation of lungs after ex vivo assessment and rehabilitation may improve organ allocation, even to distant recipients, without compromising allograft function.

Figure 1

(A) Final oxygenation (PaO₂/FiO₂) and (B) dynamic compliance at the completion of 2-hours of reperfusion. EVLP, transplantation at the completion of EVLP; EVLP+Cold, 6-hours cold preservation after EVLP and prior to transplantation; Immediate, immediate transplantation without EVLP; PaO₂/FiO₂, partial pressure of oxygen/fraction of inspired oxygen. *p<0.001 versus Immediate, #p<0.025 versus Immediate.

Figure 2

(A) Oxygenation (PaO₂/FiO₂) and (B) dynamic compliance recorded hourly during EVLP. (C) Change in oxygenation and (D) dynamic compliance from start of EVLP to completion. EVLP, transplantation at the completion of EVLP; EVLP+Cold, 6-hours cold preservation after EVLP and prior to transplantation; PaO_2/FiO₂, partial pressure of oxygen/fraction of inspired oxygen. *p<0.05

Figure 3

Oxygenation recorded at four time points: donor animal prior to hypoxia (Pre-hypoxia), 1 hour into EVLP (1-hour EVLP), at the completion of EVLP (4-hour EVLP), and recipient after 2-hours of reperfusion (Post-Reperfusion). EVLP, transplantation at the completion of EVLP; EVLP+Cold, 6-hours cold preservation after EVLP and prior to transplantation; Immediate, immediate transplantation without EVLP; PaO₂/FiO₂, partial pressure of oxygen/fraction of inspired oxygen. *p<0.001 for groups EVLP and EVLP+Cold versus Immediate.

Figure 4

Tissue cytokine levels after reperfusion. EVLP, transplantation at the completion of EVLP; EVLP+Cold, 6-hours cold preservation after EVLP and prior to transplantation; Immediate, immediate transplantation without EVLP. *p<0.05 versus Immediate.

Figure 5

Pulmonary edema after reperfusion determined by tissue wet/dry weight ratios. EVLP, transplantation at the completion of EVLP; EVLP+Cold, 6-hours cold preservation after EVLP and prior to transplantation; Immediate, immediate transplantation without EVLP; PN, recipient pneumonectomy. *p=0.01 versus PN.

Figure 6

(A) Representative histologic sections stained with hematoxylin and eosin (40× magnification). (B) Lung injury severity scores by histologic component and composite. Details of score determination can be found in Table 1. EVLP, transplantation at the completion of EVLP; EVLP+Cold, 6-hours cold preservation after EVLP and prior to transplantation; Immediate, immediate transplantation without EVLP; PN, recipient pneumonectomy. *p<0.02 versus PN.

Figure 7

Neutrophil immunohistochemistry. (A) Representative sections (40× magnification). (B) Neutrophil counts per high-powered field (HPF). EVLP, transplantation at the completion of EVLP; EVLP+Cold, 6-hours cold preservation after EVLP and prior to transplantation, Immediate, immediate transplantation without EVLP; PN, recipient pneumonectomy. #p<0.01 versus Immediate.