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What is Hyperbilirubinemia and Its Pathophysiology:Nursing Case Study

Sunday, 9 March 2014

Hyperbilirubinemia, also called neonatal jaundice, is the result of hemolytic processes in the neonate marked by an elevated serum bilirubin level and mild jaundice. It can be physiologic (with jaundice the only symptom) or pathologic (resulting from an underlying disease). Physiologic jaundice generally develops 24 to 48 hours after birth and disappears by day 7 in full-term neonates and by day 9 or 10 in premature neonates. The serum unconjugated bilirubin level doesn't exceed 12 mg/dl. Pathologic jaundice may appear anytime after the 1st day of life and persist beyond 7 days. The serum bilirubin level is greater than 12 mg/dl in a term neonate or 15 mg/dl in a premature neonate, or it increases more than 5 mg/dl in 24 hours. Physiologic jaundice is self-limiting; pathologic jaundice varies, depending on the cause. If levels are 20 mg/dl or greater in a term neonate or 14 mg/dl or greater in a premature neonate, the unconjugated bilirubin enters the extravascular tissue and collects primarily in the nuclei of the cerebral cortex and thalamus, leading to a form of encephalopathy called kirnicterus.

Pathophysiology
As erythrocytes break down at the end of their neonatal life cycle, hemoglobin separates into globin (protein) and heme (iron) fragments. Heme fragments form unconjugated (indirect) bilirubin, which binds to albumin for transport to liver cells to conjugate with glucuronide, forming direct bilirubin. Because unconjugated bilirubin is fat soluble and can't be excreted in urine or bile, its serum concentration increases (causing hyperbilirubinemia) and it may escape to extravascular tissue, especially fatty tissue and the brain.

Certain drugs (such as aspirin, tranquilizers, and sulfonamides) and conditions (such as hypothermia, anoxia, hypoglycemia, and hypoalbuminemia) can disrupt conjugation and usurp albumin-binding sites. Decreased hepatic function also reduces bilirubin conjugation. Biliary obstruction or hepatitis can cause hyperbilirubinemia by blocking normal bile flow.

Increased erythrocyte production or breakdown in hemolytic disorders or in Rh or ABO incompatibility can cause hyperbilirubinemia. Lysis releases bilirubin and stimulates cell agglutination. As a result, the liver's capacity to conjugate bilirubin becomes overloaded.

Finally, maternal enzymes in breast milk may inhibit the neonate's glucuronyl-transferase conjugating activity.

Complications
■ Kernicterus
■ Cerebral palsy, epilepsy, or mental retardation
■ Perceptual-motor disabilities and learning disorders

Assessment
Health perception and management


■ Preterm neonate with or without serious illness
■ Neonate of diabetic mother

Nutrition and metabolism
■ Withholding of food and water or late feedings (causes intestinal stasis)
■ Total parenteral nutrition or intralipid administration

Elimination
■ Bowel obstruction or reduced peristalsis

Roles and relationships (family or maternal history)
■ Hemolytic diseases, such as ABO and Rh incompatibility and severe erythroblastosis, or use of certain drugs such as vitamin K3
■ Maternal or paternal use of I.V. street drugs
■ Oxytocin‑induced labor
■ Vacuum extraction delivery

Physical examination
General appearance and nutrition

■ Poor feeding

Mental status and behavior
■ Irritability (kernicterus)
■ High‑pitched cry (kernicterus)
■ Lethargy (kernicterus)

Integumentary
■ Jaundice (light to bright yellow hue); usually progresses from head to toe, with sclerae turning yellow before skin; in preterm neonates, usually appears first on the trunk
■ Pallor caused by anemia (occurs only with severe red blood cell [RBC] hemolysis)

Respiratory
■ Apnea, cyanosis, dyspnea (later in kernicterus)
■ Asphyxia, pulmonary effusion (hydrops fetalis)

Cardiovascular
■ Generalized edema or decreased blood volume (hydrops fetalis)

Gastrointestinal
■ Poor oral feeding (refusal to take feeding or vomiting as bilirubin level rises)
■ Weight loss of up to 5% in 24 hours caused by low calorie intake from delayed bilirubin conjugation
■ Delay in passage of meconium or infrequent stools (increases enterohepatic circulation of bilirubin)
■ Hepatosplenomegaly (anemia or infection)

Neurologic
■ Hypotonia
■ Absent Moro and sucking reflexes and diminished deep tendon reflexes with encephalopathy
■ Downward gaze, irritability, elbows flexed with tight fists, rigid musculature, and opisthotonic posture as central nervous system involvement progresses
■ Seizures

Musculoskeletal
■ Tremors

Renal and urinary
■ Dark‑colored urine, becoming more concentrated as the bilirubin level rises

Diagnostic studies
■ Blood typing and Rh factor in mother and neonate determines the potential for incompatibility; the mother is screened at 28 weeks' gestation and given Rho(D) immune globulin if she is Rh-negative.
■ Coombs' test (direct) on cord blood after delivery is positive if antibodies (Rh-positive anti‑A or anti‑B) are attached to the neonate' s RBCs.
■ Coombs' test (indirect) on cord blood is positive if antibodies (Rh-positive anti‑A or anti‑B) are present in the mother's blood; may be done on the mother at intervals during pregnancy to measure increases in anti‑D antibody titer, which suggest incompatibilities.
■ Serial total bilirubin levels with an increase of more than 0.5 mg/hour to 20 mg/dl indicate the risk of kernicterus and, possibly, the need for exchange transfusion, depending on the neonate's weight and gestational age; cord bilirubin level is important, with increases of more than 4 mg/dl indicating the need for exchange transfusion, depending on whether the increase occurs 1 hour or 24 hours after delivery.
■ Direct bilirubin level increases (above 1 mg/dl) with infection or severe Rh hemolytic disease.
■ Erythrocytes from peripheral smear determine numbers, immaturity, or abnormality revealing immaturity occurring with erythroblasts in Rh and spherocytes in ABO disorders.
■ Reticulocyte count increases with hemolysis; level of 12% with hematocrit (HCT) of less than 40% indicates need for exchange transfusion.
■ Hemoglobin (Hb) level and HCT determines concentration of Hb and percentage of RBCs in blood as Hb is released when RBCs are destroyed; HCT of less than 42% and Hb level of less than 14 g/dl with hemolysis result in anemia; Hb level in cord blood of less than 12 g/dl indicates the need for exchange transfusion.
■ Total proteins determine decrease in binding sites.
■ White blood cell count with decreases of less than 5,000/mm3 or band forms increased to 2,000/mm3 indicate infection.
■ Urinalysis for specific gravity determines concentrating or reducing substance.
■ Urinalysis measures glucose, acetone, pH, urobilinogen, and creatinine levels.

Teaching checklist
■ Reasons to call the practitioner (jaundice, signs of dehydration, altered mental status, lethargy, irritability, higher‑pitched cry)
■ Assessment of the neonate's degree of jaundice
■ Care of the neonate
■ Feeding
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