Kernicterus and Hydrops Fetalis Overview
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Questions and Answers

What characterizes Kernicterus?

  • Excessive levels of bilirubin in the blood (correct)
  • Accumulation of fluid in two or more fetal areas
  • Normal levels of bilirubin in the blood
  • Only occurs during pregnancy

    • What is hydrops fetalis primarily caused by?

  • An increase in fetal heart rate
  • Excessive bilirubin levels
  • Fluid accumulation in multiple areas of the fetus (correct)
  • A decrease in maternal blood volume

    • Which laboratory test is performed on a baby if they are RhD positive?

  • Indirect Coombs test
  • Kleihauer test (correct)
  • Direct Coombs test
  • FBC on mother

    • Which of the following is NOT a clinical presentation of Hemolytic Disease of the Newborn (HDN)?

    <p>Absence of reticulocytes</p> Signup and view all the answers

    What does a direct Coombs test primarily diagnose?

    <p>Hemolytic Disease of the Newborn (HDN)</p> Signup and view all the answers

    In the context of Kernicterus, which statement is true about unconjugated bilirubin?

    <p>It penetrates neuronal membranes</p> Signup and view all the answers

    What is the purpose of the Kleihauer – Betke Acid Elution Test?

    <p>To quantify fetal hemoglobin in maternal blood</p> Signup and view all the answers

    Which of the following laboratory findings would be characteristic of a newborn with HDN?

    <p>High levels of reticulocytes</p> Signup and view all the answers

    What does the indirect Coombs test help prevent?

    <p>Transmission of maternal anti-D antibodies to the fetus</p> Signup and view all the answers

    What is the significance of a positive foetal-maternal haemorrhage (FMH) test result?

    <p>A confirmational test is required if FMH is greater than 2mls.</p> Signup and view all the answers

    How does flow cytometry help in quantifying RhD+ foetal cells?

    <p>It allows fluorescent tagging of RhD+ cells for detection.</p> Signup and view all the answers

    What is the purpose of administering RhoGAM during pregnancy?

    <p>To prevent the formation of RhD antibodies.</p> Signup and view all the answers

    What are the clinical features of ABO incompatibility?

    <p>Normocytic anaemia and jaundice.</p> Signup and view all the answers

    What does the direct Coombs test determine?

    <p>The attachment of antibodies to surface red blood cells.</p> Signup and view all the answers

    Which treatment is NOT used for hemolytic disease of the newborn (HDNB)?

    <p>Antibiotics.</p> Signup and view all the answers

    What mechanism causes maternal sensitization in Rh incompatibility?

    <p>Exposure to Rh+ blood in a previous pregnancy.</p> Signup and view all the answers

    What characterizes the pathogenesis of hemolytic disease of the newborn (HDN)?

    <p>Antigen-antibody interaction leading to tissue hypoxia.</p> Signup and view all the answers

    What is the primary cause of HDN due to ABO incompatibility?

    <p>Maternal antibodies against the ABO system.</p> Signup and view all the answers

    What is a mechanism by which RhD hemolytic disease of the newborn occurs?

    <p>Absorption of maternal antibodies by the foetus.</p> Signup and view all the answers

    Study Notes

    Kernicterus

    • A rare neurological disorder
    • Characterized by excessive bilirubin in the blood (hyperbilirubinemia)
    • Bilirubin is a breakdown product of hemoglobin
    • Normally, unconjugated bilirubin is bound to albumin and processed in the liver
    • If not processed, it accumulates in the brain, causing damage
    • Unconjugated bilirubin crosses the blood-brain barrier, damaging neuronal membranes
    • Symptoms appear 2-5 days after birth
    • Can lead to muscle tone problems, respiratory difficulties, and other neurological complications

    Hydrops Fetalis

    • Caused by fluid accumulation in two or more fetal areas, leading to swelling
    • Affected areas can include skin, lungs (pleural effusion), and the heart (pericardial effusion)
    • Severe anoxia (lack of oxygen) can result
    • Diagnosed using ultrasound

    Laboratory Testing for Hemolytic Disease of the Newborn (HDN)

    • Maternal Antibody Screening: Check for antibodies; if anemia suspected, proceed to further tests
    • Fetal Blood Count (FBC): Assess for low hemoglobin (Hb), low hematocrit, high reticulocytes (immature red blood cells), high Lactate Dehydrogenase (LDH), high unconjugated bilirubin, and low albumin
    • ABO and RhD Typing: Type the baby's blood group. If RhD negative, no further action needed. If RhD positive, perform a Kleihauer-Betke test
    • Direct Antiglobulin Test (DAT/Direct Coombs Test): Detects maternal antibodies bound to fetal red blood cells (RBCs) – diagnostic for HDN
    • Indirect Antiglobulin Test (IAT/Indirect Coombs Test): Detects maternal antibodies in serum; used for prevention of HDN; if antibodies are present, risk of HDN is predicted.

    Clinical Presentations of HDN

    • Pale yellow skin (jaundice)
    • Splenomegaly (enlarged spleen)
    • Kernicterus
    • Hydrops fetalis

    Results of FBC and Blood Film, HDN

    • Low HB
    • Low hematocrit
    • High reticulocytes
    • High LDH
    • High unconjugated bilirubin
    • Low albumin
    • Nucleated red blood cells on blood film
    • Microcytic cells (small red blood cells)

    Coombs Test

    • Also known as the antiglobulin test
    • Used to detect antibodies attacking red blood cells
    • Direct Coombs Test: Diagnoses HDN. Detects maternal anti-D antibodies already bound to fetal RBCs
    • Indirect Coombs Test: Used in prevention of HDN. Detects anti-D antibodies in the mother's serum; presence of antibodies indicates risk of HDN.

    Kleihauer-Betke Acid Elution Test

    • Quantifies fetal hemoglobin (HbF) in maternal blood
    • Fetal Hb resists acid elution; adult Hb does not
    • Maternal blood sample is analyzed and stained; ratio of fetal to adult red blood cells is calculated.
    • Negative results indicate no further testing; positive results trigger confirmatory tests if fetal-maternal hemorrhage exceeds 2 ml.

    Fetal-Maternal Hemorrhage Quantification by Flow Cytometry

    • Measures RhD+ fetal cells in the maternal circulation
    • RhD+ fetal cells fluoresce under a special light
    • Used to detect fetal-maternal hemorrhage in Rh-negative mothers with Rh-positive fetuses only

    Prevention of HDN

    • Anti-D prophylaxis (RhoGAM)
    • Administered at 28-30 weeks of pregnancy and after delivery of an Rh-positive baby to prevent mother from developing antibodies against Rh-positive blood cells

    ABO Incompatibility, Clinical and Lab Findings

    • Mild Clinical Presentation: Normocytic anemia, jaundice
    • Laboratory Diagnosis:
      • Complete Blood Count (CBC): Low Hb, low hematocrit, normal Mean Cell Volume (MCV) due to compensatory reticulocyte production
      • Direct Coombs Test: Weakly positive
      • Blood film: Shows spherocytes (spherical red blood cells)

    Treatments for HDN

    • Treat Anemia: Blood transfusions
    • Phototherapy: Treat jaundice by exposing skin to blue-green light, converting unconjugated bilirubin to water-soluble form
    • Intravenous Fluids
    • Ventilator: To assist breathing

    Fetal-Maternal Hemorrhage Mechanism

    • Rh-negative mother with Rh-positive father
    • Fetal-maternal hemorrhage in the first pregnancy
    • Mother becomes sensitized (develops antibodies) to the Rh-positive blood, but IgM antibodies don't cross placenta
    • Subsequent pregnancies, IgG antibodies form quickly and attack fetal RBCs, causing hemolysis
    • Antibodies diffuse through the placenta, coating fetal RBCs; macrophages phagocytose and lyse these cells, causing hemolysis and release more unconjugated bilirubin
    • Extramedullary hematopoiesis (production of blood outside the bone marrow) may occur

    Summary of Pathogenesis of HDN

    • Antigen-antibody interaction leading to hemolysis
    • Anemia limits oxygen delivery to fetal tissues and organs, causing anoxia
    • Antibody-coated RBCs (red blood cells) removed from the fetal circulation by macrophages in the spleen and liver

    Antibody Absorption Mechanism

    • Fetal immunization occurs when maternal antibodies enter fetal circulation via the placenta
    • Fetal absorption of maternal IgG towards the end of pregnancy, a protective mechanism, can lead to lysis of fetal red cells

    Mechanisms of RhD HDN

    • Antibody absorption
    • Fetal-Maternal Hemorrhage (FMH)

    Causes of HDN

    • Antibodies to the ABO system are a frequent cause
    • Example: Mother with blood group O, fetus with A, B, or AB blood group
    • Rh incompatibility (Rh HDN) is a more severe cause than ABO incompatibility.

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    Description

    This quiz covers essential information about Kernicterus and Hydrops Fetalis, two critical conditions in newborns. Learn about their causes, symptoms, and the importance of laboratory testing for Hemolytic Disease of the Newborn (HDN). Test your knowledge on these vital neonatal topics.

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