Jaundice

Published on 24/03/2015 by admin

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Chapter 18 Jaundice

James M. Callahan, MD, FAAP, FACEP

1 What is jaundice?

Jaundice, or icterus, is a yellow or green-yellow discoloration of the skin, mucous membranes, sclera, and body fluids caused by increased levels of circulating bilirubin. Jaundice is usually noticeable at serum bilirubin levels of 5 mg/dL.

2 Where does bilirubin come from?

The major source of bilirubin is the breakdown of heme pigment released from senescent erythrocytes. Bilirubin is usually cleared from the circulation by the liver and, once conjugated, is excreted in bile. Hemolysis that exceeds the liver’s capacity to conjugate bilirubin or processes that impair the excretion of bile cause increased bilirubin levels.

3 Is jaundice always pathologic?

Up to two-thirds of newborns develop visible jaundice at some point in the first few weeks of life. Most of these infants have “physiologic” or “breast milk jaundice” and not a pathologic process. Exclude potentially harmful causes before deciding that these benign conditions are present. In children over 3 months of age, jaundice is almost always associated with a pathologic process.

4 How do you begin the evaluation of a patient with jaundice?

First, determine whether the jaundice is due to conjugated or unconjugated hyperbilirubinemia. Conjugated hyperbilirubinemia is defined as jaundice in which the direct bilirubin level is >2 mg/dL or accounts for more than 20% of the total bilirubin. Unconjugated hyperbilirubinemia (high indirect bilirubin level) is usually due to hemolytic processes or defects in conjugation. Conjugated hyperbilirubinemia is pathologic at any age and is usually associated with cholestatic processes due to hepatic disease or anatomic obstruction to bile flow. Further workup and treatment are guided by the determination of the type of hyperbilirubinemia. The approach also varies depending on the age of the patient (newborn versus older infant/child).

6 What is kernicterus?

Kernicterus (bilirubin encephalopathy) is the most worrisome complication of neonatal unconjugated hyperbilirubinemia. At high levels, unconjugated hyperbilirubin may cross a compromised blood-brain barrier and cause lethargy, hypotonia, poor feeding, fever, seizures, and signs of increased intracranial pressure. Untreated, unrecognized, and severe cases may lead to mental retardation, cerebral palsy, and sensorineural hearing loss.

7 Which children are at risk for kernicterus?

Neonates with jaundice associated with a coexisting serious condition are most likely to develop kernicterus. Children with sepsis, hypoxia or hypercarbia, brisk hemolysis (e.g., that seen with Rh incompatibility), hypoglycemia, or prematurity are most at risk. In healthy, full-term infants, kernicterus is almost never seen at unconjugated bilirubin levels < 25 mg/dL. Premature infants and those with intercurrent illnesses may experience kernicterus at lower levels. Kernicterus, though rare, still occurs, even in otherwise healthy children born at or near term.

Ip S, Chung M, Kulig J, et al: An evidence-based review of important issues concerning neonatal hyperbilirubinemia. Pediatrics 114:e130–153, 2004.

8 What other laboratory tests are indicated in neonates with unconjugated hyperbilirubinemia?

Do a complete blood count (CBC) with differential and examination of the smear, a reticulocyte count, and direct Coombs test. Seek signs of hemolysis on the CBC. The differential may indicate an infectious process. Anemia or reticulocytosis suggest blood loss or ongoing hemolysis. If the Coombs test result is positive, isoimmunization has probably occurred (because of Rh, ABO, or minor blood group incompatibility). Determine maternal and neonatal blood types (this may be known at the hospital of delivery). Hemolysis in the absence of isoimmunization suggests a red cell defect in this age group, and a G6PD assay as well as fragility testing would be useful. Unconjugated hyperbilirubinemia in the absence of hemolysis may be seen with infections (although conjugated hyperbilirubinemia is more commonly seen), and a urinalysis, Gram stain, and culture may be helpful. If these additional studies are unremarkable, the child may have breast milk jaundice or exaggerated physiologic jaundice.

Garcia FJ, Nager AL: Jaundice as an early diagnostic sign of urinary tract in infancy. Pediatrics 109:846–851, 2002.

9 What is breast milk jaundice?

Breast-fed infants are about three times as likely as formula-fed babies to have high bilirubin levels in the first week of life. In the first few days of life, this is probably due to decreased fluid and caloric intake (until their mother’s milk is fully in) and decreased passage of meconium stools. Later in the first week of life, it has been proposed that lipase and nonesterified long-chain fatty acids in breast milk inhibit hepatic excretion of bilirubin, while the β-glucuronidase in breast milk increases enterohepatic circulation of bilirubin.

10 What is physiologic jaundice? What causes it?

Most infants (approximately two-thirds) develop visible jaundice at some point in the first week of life. The vast majority of these children have physiologic jaundice. Many factors contribute to this “normal” hyperbilirubinemia, including a large red blood cell mass, decreased survival of red blood cells, decreased hepatic uptake of bilirubin, decreased conjugation of bilirubin in the liver, and increased enterohepatic recirculation of bilirubin. Physiologic jaundice is a diagnosis of exclusion.

11 What are some indicators that jaundice is not physiologic and therefore should prompt further investigation?

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