Hepatic Dysfunction
Kevin M. Korenblat
I. GENERAL PRINCIPLES
A. Hepatic dysfunction in the intensive care unit (ICU) setting can present as one of the following:
1. Abnormalities of liver chemistries or synthetic function.
2. Signs and symptoms of liver disease (e.g., jaundice, synthetic dysfunction, and complications of portal hypertension).
B. Hepatic metabolic processes are commonly disturbed in the setting of critical illness. These processes and their normal physiology include the following:
1. Bilirubin metabolism.
a. Bilirubin is the end product of the catabolism of heme, the prosthetic moiety of hemoglobin, myoglobin, and other hemoproteins.
b. Heme from senescent erythrocytes is the source of 80% of bilirubin.
c. Unconjugated bilirubin is transported bound to albumin to the liver.
d. Bilirubin is made soluble by conjugation with glucuronic acid within the hepatocytes.
e. Conjugated bilirubin is transported into the bile canaliculus and from the bile duct into the intestine.
2. Drug metabolism.
a. The liver is frequently a site of first-pass metabolism of medications and other xenobiotics.
b. Metabolic processes can be categorized as phase I or phase II reactions.
i. Oxioreductases and hydrolases catalyze phase I reactions that increase water solubility of substances and potentially generate toxic metabolites.
ii. Transferases catalyze phase II reactions that produce biologically less active metabolites.
3. Hemostasis.
a. The liver is the site of production of many of the vitamin K-dependent coagulation factors and the anticoagulants protein C and protein S.
II. ETIOLOGY
A. Clinical disorders commonly encountered in the critical care setting that result in hepatic dysfunction include the following:
1. Ischemic hepatitis (Table 77-1).
TABLE 77-1 Causes of Ischemic Hepatitis | ||||||||||||||||||
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a. Develops in the setting of reduced liver blood flow, persistent hypotension, or severe hypoxemia.
b. A clearly defined period of hypotension may not be identifiable.
c. A variable degree of central vein (zone 3) necrosis and collapse are present on liver histology.
2. Congestive hepatopathy.
