Chapter 83: Allograft Function

INTRODUCTION

The pivotal role of the liver in the metabolism of proteins, carbohydrates, and lipids, as well as its detoxification properties, make pure liver function assessment challenging. On the other hand, the different pace of changes that are observed for the various parameters allows conclusions in a wide range of situations.

• Traditional approaches

  • Utilize serum markers of different aspects of liver metabolism

    • Carbohydrate metabolites are the fastest signs of liver metabolism

    • Synthetic function by protein synthesis

    • Bilirubin as a degradation product and marker of detoxification throughput

  • Measure the actual excretory function of the liver

    • Amount and quality of bile production

• Selective approaches

  • Utilize enzyme activities that are exclusively available in the liver

    • Indonyacin clearance

    • Galactosidase clearance

    • Antipyrine clearance

    • LiMAx

TRADITIONAL SERUM MARKERS

• Serum lactate

  • Earliest parameter indicating active or missing metabolism (1 to 2 hours after reperfusion)

  • Easily assessable by bedside measurement (blood gas analyzer)

  • As a general marker for anaerobic metabolism and insufficient tissue perfusion, several conditions can influence or increase this marker and mask sufficient liver function

• Serum glucose

  • Slightly slower reacting than serum lactate

  • Sufficient blood glucose indicates sufficient amount

    • Gluconeogenesis in the liver from:

      • Pyruvate or oxaloacetate

      • Lactate

      • Bihydroxyaceton phosphate as a derivate from glycerin from lipid metabolism

    • Glycogenolysis in the liver

• Serum coagulation tests

  • Relevant changes occur after several hours (6 to 8 hours); normalization takes one to a few days posttransplant

  • Prothrombin time (also used for international normalized ratio [INR] determination)

  • Fibrinogen testing

  • Rotational thromboelastography (analyzes several aspects of the coagulation cascade)

• Protein synthesis

  • Relevant changes are detectable a few days after transplantation; normalization takes days to a few weeks posttransplant

  • Serum cholinesterase as protein with liver origin

    • Reflection of the rate of formation of the enzyme by the liver

    • Influenced by other conditions (e.g., by hemorrhage and blood transfusion)

  • Serum albumin

    • Forms in the liver and is therefore reflective of liver protein biosynthesis

    • Persistent low values in spite of sufficient liver function in the case of albumin loss (e.g., nephrotic syndrome)

• Detoxification activity

  • Measured in the clinical setting by levels of serum bilirubin

  • Serum bilirubin

    • Relevant changes detectable one to a few days after transplantation; normalization takes several days (depending on pretransplant values), due the inclusion of bilirubin in different body tissues

    • Conjugation of bilirubin in the liver by the enzyme glucuronyltransferase

TRADITIONAL EVALUATION OF EXCRETORY LIVER FUNCTION

• Bile production

  • Prerequisite is the insertion of a T-tube into the DHC during transplantation

  • Amount of bile suggestive of liver activity

    • Thirty to 40 mL/hour in healthy organs

    • After transplantation, rate of bile production is initially commonly reduced (e.g., 15 mL/h)

    • From day to day increasing bile flow is representative of good function

  • Composition of bile suggestive of intact liver bile production

  • No certain cutoff exists for either parameter of bile production

  • Routine T-tube insertion has been abandoned in our center and is reserved for special situations