# Comparison of Normothermic and Subnormothermic Machine Perfusion of Porcine Kidneys Using a Novel Fully Synthetic Perfusion Solution: A Proof-of-Concept Study

## TL;DR

This study compares two organ preservation methods for pig kidneys using a new synthetic solution, finding each has unique benefits at different stages of preservation.

## Contribution

A novel fully synthetic perfusion solution, Omnisol, was tested for both normothermic and subnormothermic machine perfusion in an experimental setting.

## Key findings

- Normothermic perfusion showed better early functional parameters but increased injury markers after 3 hours.
- Subnormothermic perfusion maintained stable parameters and no injury marker increase during the full 6-hour period.
- Omnisol provided sufficient oxygenation for kidneys in both perfusion methods.

## Abstract

Background/Objectives: The growing shortage of organs for transplantation requires optimized preservation techniques. Normothermic (NMP) and Subnormothermic Machine Perfusion (SMP) allow for the assessment of organ viability prior to transplantation and enable targeted therapeutic interventions while maintaining a metabolically active state in contrast to hypothermic settings. Methods: In this study, the synthetic perfusion solution “Omnisol” was used in a 6 h ex vivo setting with porcine kidneys (n = 6 NMP; n = 6 SMP). Perfusion parameters (arterial flow, intrarenal resistance and urinary flow), renal function (excretory and filtration performance), renal injury (cellular and circulating biomarkers) and tissue and perfusate oxygenation were assessed. Results: NMP resulted in better arterial flow and lower intrarenal resistance during the first 3 h of perfusion, while SMP surpassed NMP from 3 to 6 h. Renal injury biomarkers increased in the NMP group after 3 h, while no increase was detectable in the SMP group. Omnisol fully met the oxygen requirements of the kidneys in both groups, despite being fully synthetic. Conclusions: Both NMP and SMP offer distinct advantages for kidney preservation, and the synthetic perfusate Omnisol appears to be feasible for both methods. In this experimental setting, the data indicate that NMP of porcine kidneys was associated with favorable functional parameters during the early phase of perfusion, whereas SMP showed comparatively stable parameters at later time points. These findings should primarily be considered exploratory observations and require validation in future studies, especially for the translation into a clinical scenario using human kidneys.