Ex vivo evaluation of porcine livers post-hypothermic machine perfusion at 4-6ºC and 12-14ºC

Abstract

Background: The goal of our research is the development of a clinical hypothermic machine perfusion method and device for liver preservation during storage and transport prior to transplantation. The purpose of this study was comparison of two hypothermic temperature ranges. Methods: Heart beating donor pig livers with 2h of static cold storage on ice were employed. Thirteen experimental livers were perfused, at either 4-6oC or 12-14oC with oxygenation, employing a prototype device. They were compared with six control 2h static cold stored livers during normothermic ex vivo blood perfusion. Physiological measurements and biochemical perfusate analyses were performed to assess the impact of storage conditions on liver functions. Statistics were assessed by one way analysis of variance, p<0.05 was regarded as significant. Results: During hypothermic perfusion perfusate solutes (Na + , K + and Ca ++ ) varied little with time. A single 12-14oC perfused liver exhibited a Ca ++ spike at 22 hours. Temperature dependent metabolic activity was observed in both groups. Lactate levels were ≤4.5mmol/L for 22h. During normothermic ex vivo testing most controls and perfusion-treated experimental livers produced bile within an hour. 10h perfusion liver lactate dehydrogenase, hyaluronic acid uptake, and total bile production were not significantly different from controls. There were trends for albumin, glucose and lactate. Significantly different Factor V, indocyanine green clearance, and blood urinary nitrogen concentrations were observed in both 10h perfusion groups. Bilirubin kinetics was perturbed in all perfusion groups, however the peak concentrations in the 10h perfusion groups were not significantly different, while the 22h 12-14oC perfusion group was significantly less than controls. A significant difference in alanine aminotransferase values between the 2 perfusion groups, was observed, however this may be due to washout during 12-14°C perfusion. Lactate dehydrogenase was doubled in both perfusion groups at 22h and individual 22h livers exhibited other assay values outside control and 10h perfusion ranges. Conclusions: Significant differences were observed between controls and both perfused groups during post hypothermic storage ex vivo assessment. These results suggest that both temperature ranges tested, with further optimization, may be suitable for liver support for up to 10h of oxygenated hypothermic perfusion. Since there were no clear advantages to 12-14°C perfusion we will continue development of a 4-6°C perfusion device for storage and transport of livers for transplantation.