A new ex-situ machine perfusion device. A preliminary evaluation using a model of donors after circulatory death pig livers

A meta-analysis of perfusion parameters affecting weight gain in ex vivo perfusion

BACKGROUND

Ex vivo machine perfusion (EVMP) has been established to extend viability of donor organs. However, EVMP protocols are inconsistent. We hypothesize that there is a significant relationship between specific parameters during EVMP and perfusion outcomes.

METHODS

A meta-analysis of literature was conducted in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) Statement. The search encompassed articles published before July 25, 2023. PubMed, Embase, and CENTRAL databases were screened using search terms "ex-vivo," "ex-situ," "machine," and "perfusion." Weight gain, an indicator of organ viability, was chosen to compare outcomes. Extracted variables included perfused organ, warm and cold ischemia time before perfusion, perfusion duration, perfusate flow, pressure, temperature, perfusate composition (presence of cellular or acellular oxygen carrier, colloids, and other supplements) and percent weight change. Data were analyzed using SPSS statistical software.

RESULTS

Overall, 44 articles were included. Red blood cell-based perfusates resulted in significantly lower weight gain compared to acellular perfusates without oxygen carriers (11.3% vs. 27.0%, p < 0.001). Hemoglobin-based oxygen carriers resulted in significantly lower weight gain compared to acellular perfusates (16.5% vs. 27%, p = 0.006). Normothermic perfusion led to the least weight gain (14.6%), significantly different from hypothermic (24.3%) and subnormothermic (25.0%) conditions (p < 0.001), with no significant difference between hypothermic and subnormothermic groups (24.3% vs. 25.0%, p = 0.952). There was a positive correlation between flow rate and weight gain (ß = 13.1, R = 0.390, p < 0.001).

CONCLUSIONS

Oxygen carriers, low flow rates, and normothermic perfusate temperature appear to improve outcomes in EVMP. These findings offer opportunities for improving organ transplantation outcomes.

Graft repair during machine perfusion: a current overview of strategies

PURPOSE OF REVIEW

With changing donor characteristics (advanced age, obesity), an increase in the use of extended criteria donor (ECD) livers in liver transplantation is seen. Machine perfusion allows graft viability assessment, but still many donor livers are considered nontransplantable. Besides being used as graft viability assessment tool, ex situ machine perfusion offers a platform for therapeutic strategies to ameliorate grafts prior to transplantation. This review describes the current landscape of graft repair during machine perfusion.

RECENT FINDINGS

Explored anti-inflammatory therapies, including inflammasome inhibitors, hemoabsorption, and cellular therapies mitigate the inflammatory response and improve hepatic function. Cholangiocyte organoids show promise in repairing the damaged biliary tree. Defatting during normothermic machine perfusion shows a reduction of steatosis and improved hepatobiliary function compared to nontreated livers. Uptake of RNA interference therapies during machine perfusion paves the way for an additional treatment modality.

SUMMARY

The possibility to repair injured donor livers during ex situ machine perfusion might increase the utilization of ECD-livers. Application of defatting agents is currently explored in clinical trials, whereas other therapeutics require further research or optimization before entering clinical research.

Interleukin-6 Levels During Normothermic Machine Perfusion Impact Postreperfusion Hemodynamics of Liver Graft Recipients: A Prospective Single-center Observational Study

BACKGROUND

Hemodynamic instability after liver graft reperfusion increases recipient morbidity after liver transplantation. The etiologies of hemodynamic disturbances appear to be multifactorial and are poorly understood. Normothermic machine perfusion (NMP) provides an opportunity to analyze graft quality prior to transplantation. In the present study, we aim to investigate the influence of interleukin-6 (IL-6) levels during NMP on postreperfusion hemodynamics of the recipient.

METHODS

Consecutive NMP-liver transplants at a single-center were prospectively analyzed. Perfusate samples were collected at the beginning, after 6 h, and at the end of perfusion and analyzed for IL-6 levels. Mean arterial pressure (MAP) and catecholamine consumption during surgery were recorded. IL-6 levels at the end of NMP were correlated to donor and perfusion characteristics as well as changes in MAP and catecholamine requirements during the anhepatic and reperfusion phase.

RESULTS

IL-6 perfusate measurements were assessed in 77 livers undergoing NMP and transplantation. Donor age, sex, cold ischemic time, and NMP time did not correlate with IL-6 levels. Perfusates of donation after circulatory death grafts showed higher IL-6 levels at the end of NMP than donation after brain death grafts. However, IL-6 levels at the end of NMP correlated with catecholamine requirements and MAP in the reperfusion phase. Per log10 increase in IL-6 levels, an increase of 42% points in administered catecholamine dose was observed, despite MAP being decreased by 3.6% points compared to baseline values.

CONCLUSIONS

IL-6 levels may be a predictor for recipient hemodynamic instability during liver reperfusion. Larger studies are needed to confirm this finding.

Hemoadsorption in Organ Preservation and Transplantation: A Narrative Review

Cytokine adsorption can resolve different complications characteristic of transplantation medicine, such as cytokine storm activation and blood ABO and immune incompatibilities. Cytokine adsorption is also performed for the treatment of various life-threatening conditions, such as endotoxic septic shock, acute respiratory distress syndrome, and cardiogenic shock, all potentially leading to adverse clinical outcomes during transplantation. After surgery, dysmetabolism and stress response limit successful graft survival and can lead to primary or secondary graft dysfunction. In this clinical context, and given that a major problem in transplant medicine is that the demand for organs far exceeds the supply, a technological innovation such as a hemoadsorption system could greatly contribute to increasing the number of usable organ donors. The objectives of this review are to describe the specific advantages and disadvantages of the application of cytokine adsorption in the context of transplantation and examine, before and/or after organ transplantation, the benefits of the addition of a cytokine adsorption therapy protocol.