The liver, the largest parenchymal organ in the body, receives 25% of the resting cardiac output . It is also a complex metabolic organ involved in a variety of synthetic and detoxification functions. By virtue of its size, multiple metabolic functions, and prominent position in the circulatory system, the liver is frequently involved in systemic, circulatory, and inflammatory diseases. It is often an “innocent bystander” during systemic diseases; conversely, hepatic dysfunction may be the first clue to a systemic disorder. This chapter reviews hepatic involvement in common childhood systemic diseases.
JAUNDICE IN THE CRITICALLY ILL CHILD
Hepatic dysfunction, manifest as jaundice, occurs in patients with systemic diseases associated with increased bilirubin production, ischemia, hypoxemia, or malnutrition (Table 38.1). Bilirubin production increases with hemolysis, blood transfusions, intraluminal bleeding, extracorporeal oxygenation, and resorption of blood from hematomas. The inflammatory cascade has multiple effects on hepatic function [2–9]. In the healthy patient, the liver has the capacity to conjugate and excrete bilirubin. However, with fasting, malnutrition, positive pressure ventilation, or ischemia, the liver's ability to process bilirubin is compromised and conjugated hyperbilirubinemia results [10, 11] (Figure 38.1). Liver dysfunction improves with correction of the primary disorder, but inadequate or unsuccessful treatment may result in progressive hepatic dysfunction.
Jaundice and conjugated hyperbilirubinemia occur more frequently in infants and children with sepsis, even in the absence of shock. Patients may have mildly elevated serum alkaline phosphatase and aminotransferase levels; isolated hyperbilirubinemia is uncommon [12, 13].