Criteria for Viability Assessment of Discarded Human Donor Livers during Ex Vivo Normothermic Machine Perfusion

Abstract

Although normothermic machine perfusion of donor livers may allow assessment of graft viability prior to transplantation, there are currently no data on what would be a good parameter of graft viability. To determine whether bile production is a suitable biomarker that can be used to discriminate viable from non-viable livers we have studied functional performance as well as biochemical and histological evidence of hepatobiliary injury during ex vivo normothermic machine perfusion of human donor livers. After a median duration of cold storage of 6.5 h, twelve extended criteria human donor livers that were declined for transplantation were ex vivo perfused for 6 h at 37°C with an oxygenated solution based on red blood cells and plasma, using pressure controlled pulsatile perfusion of the hepatic artery and continuous portal perfusion. During perfusion, two patterns of bile flow were identified: (1) steadily increasing bile production, resulting in a cumulative output of ≥30 g after 6 h (high bile output group), and (2) a cumulative bile production <20 g in 6 h (low bile output group). Concentrations of transaminases and potassium in the perfusion fluid were significantly higher in the low bile output group, compared to the high bile output group. Biliary concentrations of bilirubin and bicarbonate were respectively 4 times and 2 times higher in the high bile output group. Livers in the low bile output group displayed more signs of hepatic necrosis and venous congestion, compared to the high bile output group. In conclusion, bile production could be an easily assessable biomarker of hepatic viability during ex vivo machine perfusion of human donor livers. It could potentially be used to identify extended criteria livers that are suitable for transplantation. These ex vivo findings need to be confirmed in a transplant experiment or a clinical trial.

Liver Transplantation After Ex Vivo Normothermic Machine Preservation: A Phase 1 (First-in-Man) Clinical Trial

“…bile output) parameters during perfusion and that this may allow clinically useful viability testing (25). This hypothesis is supported by a recently published study of perfused discarded livers, suggesting that bile output and other metabolic parameters may differentiate viable from nonviable livers (26). If this is validated in a clinical environment, then the risk associated with marginal organs will be reduced, by enabling clinicians to accept an organ provisionally, secure in the knowledge that further information will become available before committing the patient to the risk of a transplant.…”

Development of a normothermic extracorporeal liver perfusion system toward improving viability and function of human extended criteria donor livers

“…Historically, measuring "bile production" and concentration of coagulation factor V (enzyme-linked immunosorbent assay [ELISA]) have been used as markers of liver viability and functionality. (28)(29)(30) Unfortunately, bile production is a very "subjective" measurement, and to date, there has not been any published study about the acceptable range for "satisfactory" bile production in ex vivo models. Moreover, livers that do not make bile in a short period of NELP may start producing bile later in the course of warm perfusion.…”

“…Adding TPN or some kind of nutritional supplementation to the NELP circuit has been previously reported by several other groups. (28,30,(36)(37)(38) However, the exact dosing of the TPN and the metabolic consequences of adding this solution during machine perfusion has yet to be investigated. Therefore, further mechanistic studies are needed to uncover the specific allograft supplemental requirements and to deeply understand the metabolic pathways changes during ex vivo perfusion experiments.…”

“…In many studies (including ours), despite an initial immediate increase in the glucose levels upon connecting the liver to the NELP system, a constant reduction of glucose has been reported. (28,36,46) In fact, it has been shown that a constant reduction in perfusate glucose concentrations during NELP is accompanied by increased glycogen storage in the hepatocytes. (47) On the other hand, glucose decline during NELP is a good sign of liver functionality and shows that the glucose is constantly being picked up by the hepatocytes and is being stored as glycogen.…”

Functional Human Liver Preservation and Recovery by Means of Subnormothermic Machine Perfusion

“…In particular, the biliary complications that currently plague suboptimal-quality liver grafts after transplantation remain a substantial issue [14][15][16][17][18] . Machine perfusion at subnormothermic conditions provides a time window to assess graft function objectively as to suitability for transplantation 19 . While the liver is being perfused in an ex vivo circuit, both the perfusate and the bile produced during perfusion can be sampled for measurement of markers of organ function.…”