Comprehensive Approach to Assessment of Liver Viability During Normothermic Machine Perfusion

Abstract

Liver transplantation is the most effective treatment of advanced liver disease, and the use of extended criteria donor organs has broadened the source of available livers. Although normothermic machine perfusion (NMP) has become a useful tool in liver transplantation, there are no consistent criteria that can be used to evaluate the viability of livers during NMP. This review summarizes the criteria, indicators, and methods used to evaluate liver viability during NMP. The shape, appearance, and hemodynamics of the liver can be analyzed at a macroscopic level, while markers of liver injury, indicators of liver and bile duct function, and other relevant indicators can be evaluated by biochemical analysis. The liver can also be assessed by tissue biopsy at the microscopic level. Novel methods for assessment of liver viability are introduced. The limitations of evaluating liver viability during NMP are discussed and suggestions for future clinical practice are provided.

Modification of Preservative Fluids with Antioxidants in Terms of Their Efficacy in Liver Protection before Transplantation

“…By using normothermic machine perfusion, the percentage of grafts eligible for transplantation can be increased. This method allows real-time liver and bile duct function assessment and can predict short-term transplantation outcomes [111]. It has been suggested that using NMP after the initial SCS period facilitates the regeneration of impaired cellular metabolic processes [112].…”

Normothermic machine perfusion for liver transplantation: current state and future directions

“…All available machine perfusion devices allow for calculation of arterial and portal flows. Increased vascular resistance resulting in decreased arterial and portal flow may be an indicator of liver injury [22]. Decreased flow can also be consistent with the presence of fibrosis or cirrhosis or even macrosteatosis with secondary sinusoidal stenosis and reduced perfusion [23,24].…”

“…Decreased flow can also be consistent with the presence of fibrosis or cirrhosis or even macrosteatosis with secondary sinusoidal stenosis and reduced perfusion [23,24]. Several studies have included measures of liver perfusion as part of their viability criteria [12,22,25,26]. Although a specific value or cut-off for viability has not yet been determined, flows of more than 150 ml/ min for the hepatic artery and more than 500 ml/min for the portal vein have been proposed [16 & ].…”

“…There is conflicting evidence around the use of liver enzyme levels for alanine transaminase (ALT) and aspartate aminotransferase (AST) as measures of organ viability [22]. Early studies prior to the use of NMP found the peak AST and ALT do not correlate with graft function posttransplant [29][30][31].…”

“…Although a specific value or cut-off for viability has not yet been determined, flows of more than 150 ml/min for the hepatic artery and more than 500 ml/min for the portal vein have been proposed [16 ▪ ]. Other groups recommend adjusting flow to account for liver volume, requiring 0.1 ml/min/g for hepatic artery and 0.33 ml/min/g for portal vein flows [22]. There are several techniques currently under investigation that may more accurately measure liver perfusion, including hyperspectral imaging and indocyanine green (ICG) clearance; however, none are routinely used in clinical practice [27,28].…”