Bilirubin Metabolism and Exchange Transfusion

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Questions and Answers

What is the term for the yellowish discoloration of the skin and other organs caused by excessive bilirubin?

Thrombosis

Icterus (correct)

Anemia

Leukemia

Which enzyme in the liver is responsible for conjugating bilirubin?

Trypsin

Amylase

Glucuronyl transferase (correct)

Lipase

What is the primary purpose of conjugating bilirubin in the liver?

To increase its binding to albumin

To convert it into a storage form.

To make it more soluble for excretion (correct)

To make it toxic to the body

What is the main source of unconjugated bilirubin in the body?

Breakdown of hemoglobin from red blood cells (B) Signup and view all the answers

How is the majority of conjugated bilirubin eliminated from the body?

Through the feces (A) Signup and view all the answers

What is the typical volume of donor blood used in an exchange transfusion?

Double the infant's blood volume (D) Signup and view all the answers

Which of the following is NOT a purpose of an exchange transfusion?

Raising the serum bilirubin level (C) Signup and view all the answers

What is the approximate percentage of the neonate's blood that is replaced by a double-volume exchange transfusion?

85% (C) Signup and view all the answers

Where is the catheter typically inserted during an exchange transfusion?

Umbilical vein (A) Signup and view all the answers

Which of these conditions is a risk or complication of exchange transfusion?

Hypomagnesemia (C) Signup and view all the answers

What monitoring is crucial during an exchange transfusion procedure?

Cardiopulmonary monitoring (C) Signup and view all the answers

Which medication should typically be administered after an exchange transfusion?

Vancomycin (B) Signup and view all the answers

Which of these is an indication for exchange transfusion in a neonate with hyperbilirubinemia?

Rapidly increasing serum bilirubin levels despite aggressive phototherapy (D) Signup and view all the answers

What action should be taken if an infant shows signs of cardiac or respiratory distress during a blood exchange?

Stop the procedure temporarily and resume once the infant's condition stabilizes. (C) Signup and view all the answers

Besides cardiorespiratory status, what should a nurse monitor for during an exchange transfusion?

Temperature instability and rash. (B) Signup and view all the answers

How often should the blood bag be shaken during an exchange transfusion?

Every 15 minutes (B) Signup and view all the answers

What is the recommended frequency for total serum bilirubin (TSB) laboratory studies after an exchange transfusion?

Every 4 hours (C) Signup and view all the answers

What is a critical aspect of post exchange care for the neonate?

Continue photo therapy (C) Signup and view all the answers

Study Notes

Neonatal Jaundice (NNJ)

Neonatal jaundice, also known as hyperbilirubinemia, is a condition characterized by yellowish discoloration of skin and other organs due to excessive bilirubin accumulation in the blood.
Bilirubin metabolism is crucial for bilirubin clearance; it needs to be conjugated in the liver, excreted in bile, and eliminated through urine and stool.
Unconjugated bilirubin, an insoluble form, is bound to albumin, while conjugated bilirubin, a water-soluble form, is excreted in the bile.
In the intestine, conjugated bilirubin is reduced to urobilinogen, which gives stool its color.
Most reduced bilirubin is excreted in feces; a small amount is eliminated in urine.
Physiologic (developmental) factors, an association with breastfeeding, excess bilirubin production, and disturbed liver function can cause NNJ.
Some disease states and genetic predispositions are also involved in a pathologic cause of NNJ.

Lecture Objectives

Describe bilirubin metabolism
Understand the clinical significance of hyperbilirubinemia
Learn the diagnostic approach and further work-up
Distinguish between indirect and direct hyperbilirubinemia
Develop differential diagnoses for each type
Understand management options for each type

Hyperbilirubinemia

Represents an imbalance between bilirubin production and elimination.
Bilirubin is a breakdown product of hemoglobin from red blood cell destruction.
Heme is split into globin (protein) and heme (an insoluble substance bound to albumin).
In the liver, bilirubin is conjugated with glucuronic acid, creating a highly soluble form.
Conjugated bilirubin is then excreted into the bile.

Definition

Hyperbilirubinemia refers to an excessive level of accumulated bilirubin in the blood, characterized by jaundice (icterus), a yellowish discoloration of skin and other organs.
Most instances of hyperbilirubinemia in newborns are relatively benign.
In extreme cases, it can indicate a pathologic state.

Pathophysiology

Bilirubin is a byproduct of red blood cell breakdown.
When red blood cells are destroyed, heme and globin are released.
Globin is reused, while heme is broken down to unconjugated bilirubin (insoluble).
Unconjugated bilirubin is transported bound to albumin to the liver.
In the liver, bilirubin is detached from albumin and conjugated with glucuronic acid.
Conjugated bilirubin is water-soluble and excreted into bile.
In the intestine, bacteria convert conjugated bilirubin into urobilinogen, which gives stool its color.
Most urobilinogen is excreted in feces.

Physiologic Jaundice

Cause: Immature hepatic function, increased bilirubin load (RBC hemolysis), enterohepatic shunting.
Onset: After 24 hours (prolonged in preterm), peak 2nd–5th day, duration 5th–7th day.
Therapy: Increased feeding frequency; avoid supplements; evaluate stooling pattern; monitor TcB/TSB; risk assessment; phototherapy if needed.

Breastfeeding-Associated Jaundice (Early Onset)

Cause: Decreased milk intake related to fewer calories consumed by the infant before adequately established milk supply, enterohepatic shunting, less frequent stooling.
Onset: 3rd–4th day, peak 3rd–5th day, variable duration.
Therapy: Breastfeed frequently; avoid supplements; evaluate stooling pattern; perform risk assessment; phototherapy may be required.

Breast Milk Jaundice (Late Onset)

Cause: Possible factors in breast milk that prevent bilirubin conjugation, less frequent stooling.
Onset: 4th day, peak 10th–15th day, may persist for 3–12 weeks.
Therapy: Increase breastfeeding frequency, avoid supplements; perform risk assessment; temporary cessation of breastfeeding may be considered and subsequent TSB may be evaluated.

Hemolytic Disease

Cause: Blood antigen incompatibility causing hemolysis of large numbers of red blood cells (RBCs), functional inability of liver to conjugate and excrete excess bilirubin from hemolysis.
Onset: During the first 24 hours (levels increase ≥5 mg/dL/day).
Peak: Variable.
Duration: Depends on severity and treatment.
Therapy: Monitor TCB/TSB levels; risk assessment; postnatal phototherapy, tin-mesoporphyrin, intravenous immunoglobulin; prenatal intrauterine transfusion; Rh immune globulin (RhIg) administration.

Complications

Unconjugated bilirubin is extremely toxic to neurons.
Bilirubin encephalopathy describes varying degrees of acute symptoms of bilirubin toxicity in the brain.
Kernicterus is bilirubin-induced neurologic dysfunction; yellow staining of brain cells and brain cell necrosis result in chronic, permanent changes.

Diagnostic Evaluation

TSB: Normal values for unconjugated bilirubin in newborns are 0.2 to 1.4 mg/dL; levels over 5 mg/dL imply jaundice.
Risk Assessment: Factors associated with pathologic hyperbilirubinemia include jaundice appearing within 24 hours, elevated serum bilirubin levels in the high-risk zone, blood group incompatibility with positive Direct Coombs test, hereditary hemolytic disease (e.g., G6PD), gestational age 35 to 36 weeks, East Asian or Asian-American race, cephalhematoma or significant bruising, exclusive breastfeeding, and a history of a sibling with hyperbilirubinemia.
Monitoring (Transcutaneous bilirubinometer, TcB): Accurate measurements within a 2-3 mg/dL range for serum bilirubin levels below 15 mg/dL are achievable.

Kramer's Index

A method for grading the extent of jaundice based on visual inspection of the skin.
Visual inspection is subjective and needs accurate measurements of serum bilirubin levels.
The severity of jaundice is graded from 1 to 5, representing the extent of body areas affected (face, upper body, lower body, extremities, palms/soles).

Diagnostic Studies

Include frequent assessment of blood type, Rh factor, direct and indirect Coombs test, complete blood count (CBC), reticulocyte count, blood smear, and albumin levels.
Occasional imaging studies (liver/GB ultrasound, HIDA scan) may be warranted to rule out biliary atresia.

Treatment

Goals: Prevent bilirubin encephalopathy and/or kernicterus, and, if applicable, reverse the hemolytic process.
Methods: Phototherapy, exchange transfusion if phototherapy is ineffective, and appropriate feeding (encouraging frequent breastfeeding).
Medications: Phenobarbital, possibly IVIG is effective for reducing bilirubin levels in infants with Rh- or ABO incompatibility.

Feeding Management

Evaluate stooling frequency; increased feeding frequency is essential in some instances.
Monitoring weight, voiding pattern, and stooling are also important aspects of management.

Nursing Care

Routine physical assessment includes jaundice, skin color assessment using natural daylight and direct pressure on bony prominences.
Use a transcutaneous bilirubinometer for non-invasive measurements.
Obtain a careful history from parents regarding family history.
Assess hydration status.

Hemolytic Disease of the Newborn (HDN)

Characterized by hyperbilirubinemia in the first 24 hours due to rapid red blood cell destruction.
Anemia from RBC destruction leads to accelerated erythropoiesis, resulting in immature red blood cells in the fetal circulation (erythroblastosis fetalis).
Major causes are Rh and ABO incompatibilities.

ABO Incompatibility

May result in hemolytic disease in newborns when the mother's blood type is different from the baby's.
Antibodies in the mother's blood can cross the placenta, attach to the baby's red blood cells, and cause hemolysis.
The reaction is typically less severe than Rh incompatibility.

Intrauterine Transfusion

Infusion of blood into the umbilical vein of the fetus.
Used for cases with significant fetal anemia, based on confirmed maternal-fetal blood incompatibility.

Exchange Transfusion

A procedure to reduce elevated bilirubin levels in severely affected infants with hemolytic disease.
Fresh, cross-matched blood is used to replace the infant's blood.
Risks of exchange transfusions include cardiac and respiratory disturbances; shock; electrolyte imbalances (hyper/hypokalemia, hyper/hypoglycemia, hypocalcemia); infections; and complications due to clotting, air embolism and portal hypertension.
Procedure involves insertion of a catheter into the umbilical vein and monitoring of vitals and complications.

Prevention of Rh Isoimmunization

Rh immunoglobulin (RhIg) administration to Rh-negative mothers (within 72 hours of delivery, miscarriage, etc.; and at 26 to 28 weeks of gestation).
RhIg is not effective against existing Rh-positive antibodies.
RhIg is administered intramuscularly to the mother and not to the infant.

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Description

This quiz covers key concepts related to bilirubin metabolism, including the causes of jaundice and the process of exchange transfusion in neonates. Test your knowledge on the enzymatic processes, transfusion procedures, and complications associated with these medical practices.