Darren H. Freed

Background.: Ex vivo lung perfusion (EVLP) has expanded the use of donor lungs by enabling ex vivo assessment, preservation, and rehabilitation before transplantation. Despite these advances, ischemia-reperfusion injury, inflammatory activation, pulmonary edema, and impaired lung mechanics continue to compromise graft quality and contribute to primary graft dysfunction. Inhaled and gaseous interventions have emerged as potential adjunctive therapies to improve donor lung preservation during EVLP; however, a standardized protocol has not yet been established. Methods.: PubMed and Embase were used to search human and animal studies evaluating inhaled and gaseous interventions administered during and after EVLP. Articles published from the database’s inception to September 22, 2025, were analyzed. Results.: Among the interventions examined, 10% carbon dioxide, carbon monoxide (CO), 40% oxygen (O ₂ ), hydrogen, 40 ppm nitric oxide (NO) with 60% O ₂ , 2% sevoflurane with 40%–50% O ₂ , 2-S-amino-6-boronohexanoic acid, fasudil, and β ₂ -adrenoreceptor agonists most effectively improved lung function. Interestingly, improvements from hydrogen and CO were observed after transplantation, rather than during EVLP, suggesting more persistent or delayed protective effects. Further optimized parameters were observed when moderate O ₂ concentrations (40%–60%) were combined with either CO, NO, or sevoflurane, compared with O ₂ alone. In contrast, argon, xenon, N-acetylcysteine, sevoflurane or NO with 6% O ₂ , and liquid ventilation demonstrated minimal benefit. Conclusions.: Inhaled interventions can attenuate both mechanical damage and inflammatory pathways, particularly when used in tailored combinations with 40%–60% O ₂ . Future research should prioritize standardizing protocols, optimizing gas composition and timing, and assessing long-term posttransplant outcomes to translate these findings into clinical practice.

Background.: Ex-situ heart perfusion (ESHP) enables improved donor heart preservation, yet still suffers functional decline. The perfusate is 1 area that requires optimization, especially with regard to hemoglobin (Hb) content. We sought to compare performance of concentrated, physiologic, and dilute perfusates in minimally damaged hearts. Methods.: Hearts of juvenile Yorkshire pigs (45–55 kg) were procured and subject to 11 h of working-mode ESHP in 1 of 4 groups varying in Hb: concentrated blood (CB, ~12 g/dL Hb, n = 4), whole blood (WB, ~8g/dL Hb, n = 6), plasma (~4g/dL Hb, n = 6, diluted with donor plasma), and control (~4g/dL Hb, n = 5, diluted with modified Krebs-Heinseleit). Functional, metabolic, and hemolytic markers were recorded and compared between groups statistically using appropriate statistical tests. Results.: CB hearts exhibited worsened decline from baseline in cardiac index, dP/dT max/min, and stroke work ( P < 0.05) and had greater elevations in hemolytic markers by end perfusion. Preservation of baseline cardiac index did not differ significantly between controls, WB, or plasma groups over time ( P > 0.05). The CB group displayed elevated early oxygen consumption compared with controls ( P < 0.05), with WB and plasma groups trending toward increased oxygen consumption. Lactate elevated over time in all groups, however, was not comparatively elevated within the CB group; it was reduced in the plasma group during early perfusion compared with control. Conclusions.: Hb dilution appears to lower absolute output but preserves baseline function. Supraphysiologic Hb elevation or sublethal blood cell damage exacerbates hemolysis, which contributes to functional decline during ESHP. Lactate evolution did not appear to associate with the degree of functional loss.

Background.: Von Willebrand factor (VWF) is a procoagulant glycoprotein expressed exclusively in endothelial cells and megakaryocytes. It mediates platelet adhesion to endothelial/subendothelial surfaces and initiates thrombogenesis. External stimuli, including hypoxia, were shown to upregulate VWF expression levels and alter its vascular tree expression pattern in the lung. Increased VWF levels are a significant risk factor for thrombus formation, a major complication in organ transplantation. Given that donor organs experience hypoxic conditions during transplantation, this study investigates whether hypoxia alters VWF expression and whether modifying organ preservation to reduce hypoxic exposure could prevent these alterations. Methods.: Porcine procured lungs were maintained in either static cold storage (SCS) or ex vivo lung perfusion with warm perfusion. Lung tissue biopsies were obtained immediately after organ procurement, 12 h post–cold storage, or post–warm perfusion. VWF RNA and protein expression levels and patterns were analyzed using reverse transcriptase-polymerase chain reaction, Western blot, and immunofluorescence. Results.: Immunofluorescent analysis demonstrated that transplanted lungs maintained under SCS, but not ex vivo lung perfusion, exhibited VWF expression in an increasing number of microvascular endothelial cells, whereas warm perfusion led to a significant reduction in VWF mRNA levels, and it also showed a clear trend toward reduced protein expression compared with cold storage. Conclusions.: Increased VWF expression in microvascular endothelial cells under SCS may contribute to transplant-associated thrombogenicity. Decreasing VWF expression through ex vivo normothermic perfusion could significantly mitigate the risk of thrombogenic complications, a major complication of organ transplantation.

Ex-situ heart perfusion (ESHP) is an innovative technology that has the power to greatly improve donor heart utilization and may eventually provide a platform for improvement of suboptimal hearts. However, its impact is limited by functional decline whilst on the platform, which is characterized by the development of oxidative stress and inflammation. Pathologic metabolism during normothermic ESHP may be an underlying factor in the development of such characteristics, however it is understudied within the context of machine perfusion. In the following review article, we discuss the limitations of the current metabolic substrate provision approach during ESHP (analogous to post-prandial glucose and insulin) from a mechanistic standpoint. We discuss alternative approaches and substrates that may be more conducive to physiologic preservation and recovery on the platform. We advocate for a support strategy mimicking fasting insulin and glucose, and alternative substrates such as free fatty acids and ketone bodies, which may be more adapted to the non-physiologic state encountered during ESHP. Throughout, we outline research gaps yet to be explored that would enable substrate provision approaches during machine perfusion of the donor heart to be further optimized.