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Perinatal Issues and Transfusion lecture
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Perinatal Issues and Transfusion lecture

Introduction to Perinatal Issues and Transfusion Medicine

In this section, Chris Reader, the laboratory supervisor at the Hematology Reference Lab, introduces the topic of perinatal issues and transfusion medicine. He highlights the importance of this topic for the ASAP board exam and hospital laboratories.

Objectives

  • Understand what HDFM (Hemolytic Disease of the Fetus and Newborn) is and the role of medical technologists in diagnosing and managing it.
  • Compare HDFM with RHD HDFN (Rh Hemolytic Disease of the Fetus and Newborn) in terms of similarities and differences.
  • Learn about indications for Rh immune globulin administration and tests for detecting and quantifying fetal hemorrhage.
  • Explore neonatal exchange transfusion requirements based on blood groups and special characteristics.

Understanding HDFN

This section provides an overview of HDFN, explaining how maternal antibodies can cross the placenta, leading to complications for the fetus. It also discusses compensatory mechanisms in babies to counteract red cell destruction.

Key Points

  • Maternal IGG antibodies can freely cross the placenta during pregnancy.
  • When these antibodies target antigens on fetal red cells, it can result in anemia or accumulation of unconjugated bilirubin after delivery.
  • The rate of destruction depends on antibody strength and specificity.
  • Babies have compensatory mechanisms like extra-hematopoiesis outside the bone marrow.
  • Excessive hematopoiesis can lead to splenomegaly, hypertension, liver damage, anemia, hydrops fetalis (severe edema), or erythroblastosis fatalis (release of immature red blood cells).

Complications of HDFN

This section discusses the complications that can arise from HDFN, including liver and brain damage due to bilirubin accumulation.

Key Points

  • Excessive hematopoiesis can overwhelm the liver, leading to insufficient production of plasma proteins and decreased osmotic pressure.
  • Unconjugated bilirubin levels can reach toxicity in moderate or severe HDFN cases.
  • High levels of unconjugated bilirubin can accumulate in the baby's brain after delivery, causing permanent brain damage (kernicterus).
  • ABO HDFN tends to be milder than Rh HDFN and can be treated with phototherapy.
  • RHD antibodies are only produced after exposure to the antigen, making RHD HDFN more severe. It is preventable with Rh immune globulin administration.

Management and Testing

This section focuses on management strategies for HDFN, including intrauterine or exchange transfusion. It also mentions the importance of screening for antibodies during pregnancy.

Key Points

  • In the first trimester, mothers are asked about previous pregnancies and complications related to antibody production.
  • Type and screen tests are performed if the antibody screen is positive.
  • Antibodies must be identified and titrated to assess the risk level.
  • Severe anemia due to RHD HDFN can be treated with intrauterine or exchange transfusion after delivery.

The transcript does not provide timestamps for all sections.

New Section

This section discusses the importance of repeat testing for critical results and the use of Doppler Imaging to assess neonates for hemolysis.

Repeat Testing and Doppler Imaging

  • A result of 16 is considered critical and requires repeat testing at 18 to 20 weeks gestation.
  • A four-fold increase or two tubes in a serial dilution indicates exposure to the corresponding antigen.
  • Doppler Imaging of the median cerebral artery can be used to determine peak systolic velocity and assess neonates for hemolysis.

New Section

This section explains how fetal assessment for antigen expression can be done through serological phenotype testing or predictive molecular genotype testing.

Fetal Assessment for Antigen Expression

  • Fetal assessment for antigen expression can be done by testing the father's serological phenotype or performing a predictive molecular genotype.
  • Serological phenotype testing was once commonly used to determine RHD status but may become popular again to limit the usage of Rh immune globulin.

New Section

This section describes different techniques for collecting cord blood samples and emphasizes the need to remove clots before testing.

Cord Blood Collection Techniques

  • Neonatal testing is performed on blood collected from the umbilical cord after delivery.
  • Two collection techniques include squeezing out blood into an EDTA tube or using a syringe to draw blood directly from the umbilical vein.
  • The first method often results in clots that need to be removed with wooden applicator sticks before testing.
  • It is recommended to wash red cell suspension multiple times prior to testing to remove Wharton's jelly, which can interfere with test results.

New Section

This section explains the process of cord blood testing and the use of anti-IGG for DAT testing.

Cord Blood Testing

  • Cord blood testing involves forward RH typing and a direct antiglobulin test (DAT) using anti-IGG.
  • Neonates do not have well-developed immune systems, so reverse typing is not necessary.
  • It is important to remove any Wharton's jelly present in the cord blood before testing.

New Section

This section discusses further testing required if the DAT is positive and different methods for verifying antibody binding to neonatal red blood cells.

Verification of Antibody Binding

  • If the DAT is positive, an elution is performed to verify which antibody is binding to neonatal red blood cells.
  • A Louis freeze-thaw elution can be used when there is serological incompatibility between the mother and neonate.
  • In cases where the mother has a positive antibody screen, an acid elution may be performed to recover other types of antibodies.

New Section

This section explains the administration of RH immune globulin (RIG or Rhogam) to pregnant women and its mechanism of action.

Administration of RH Immune Globulin

  • RH immune globulin (RIG or Rhogam) is given to pregnant RHD-negative women during pregnancy and at delivery if the neonate is RHD-positive.
  • RIG saturates D antigen binding sites, preventing priming of memory B cells and production of anti-D antibodies.
  • RIG should only be administered if the mother has not already developed antibodies against the antigen.

Anagenic Exposure to the Mother and Fetal Bleed Screen

This section discusses anagenic exposure to the mother after pregnancy, specifically during placental rupture, and the importance of performing a fetal bleed screen.

Anagenic Exposure and Fetal Bleed Screen

  • Anagenic exposure to the mother occurs after pregnancy, particularly during placental rupture.
  • Multiple doses of medication may be given within 72 hours of delivery to determine if a maternal hemorrhage has occurred in an RHD negative mother.
  • In an RHD negative mother, a fetal bleed screen is performed to estimate the amount of fetal blood present in the mother's circulation.
  • The fetal bleed screen can only be used if the mother is truly RHD negative. If she is partial D, then the client power bet key test should be performed instead.
  • The fetal bleed screen relies on the anti-D reagent and may potentially react with maternal cells, leading to false-positive results.
  • To perform the fetal bleed screen, a drop of anti-D reagent is added to three test tubes. A drop of maternal red blood cell suspension is added to one tube, while positive and negative controls are added to the other two tubes.
  • After incubation at room temperature, any unbound antibody is washed away. RHD positive indicator cells are then added, which bind to anti-D bound to fetal red blood cells (RBCs), forming rosettes.
  • Rosettes are not visible macroscopically but can be observed under a bright field microscope. If at least five rosettes are seen in five fields, the test is considered positive.
  • If the fetal bleed screen is positive or skipped due to partial D status, further quantification of the fetal bleed must be done using clihauer vet key test.

Clihauer Vet Key Test

This section explains the clihauer vet key test, which is used to quantitate the fetal bleed.

Clihauer Vet Key Test

  • The clihauer vet key test is performed to quantitate the fetal bleed.
  • It is most often performed in the hematology department of a hospital laboratory but can also be done in a hospital blood bank.
  • To perform the test, maternal whole blood is used to create a blood smear. Positive and negative controls are also prepared using cord blood and a male patient specimen without cord blood, respectively.
  • An acid reagent is added to lace adult cells while fetal cells resist acid elution. After rinsing off the acid reagent, a buffering reagent is added for 8 to 10 minutes.
  • A fuchsia counter stain is then applied, which is taken up by living fetal cells. Fetal cells appear darker stained compared to adult cells on the slide.
  • Normally, counting 2,000 cells and dividing the number of fetal cells by the total count provides the percentage of fetal cells. However, an easier method involves using a Miller disc microscope ocular with specific boxes for counting adult and fetal cells.
  • Once the percentage of fetal cells is determined, it can be multiplied by maternal blood volume to estimate the amount of fetal blood requiring treatment with Rho(D) immune globulin (RIG).
  • Due to poor reproducibility of this test, an extra vial of RIG should be added as a precautionary measure.

Conclusion

This section concludes by emphasizing that there will likely be at least one clihauer vet key calculation on board exams due to its significance in determining RIG dosage.

Conclusion

  • The clihauer vet key test plays a crucial role in determining the dosage of Rho(D) immune globulin (RIG).
  • Due to its importance, it is highly likely that there will be at least one clihauer vet key calculation on board exams.

Calculation of Fetal Blood Volume

In this section, the speaker discusses the calculation of fetal blood volume and the percentage of field bleed.

Calculation Steps

  • Divide 54 into 2000 to determine the percentage of field bleed, which is 2.7%.
  • Multiply 2.7% by the estimated maternal blood volume (usually expressed as 5000 milliliters) to obtain an estimated 135 milliliters of fetal blood.
  • Divide the amount of fetal blood (135 milliliters) by 30 (the amount covered by each vial of RIG) to get approximately 4.5.
  • Round up to the nearest whole number if the decimal is .5 or higher. In this case, round up to 5.
  • Add one more vial for a total of six vials of RIG.

Intrauterine Transfusion and Therapeutic Threshold

This section covers intrauterine transfusion and the therapeutic threshold for fetal anemia.

Intrauterine Transfusion

  • If intrauterine transfusion is necessary based on imaging techniques or cord synthesis, donor red blood cells can be injected into the umbilical vein.
  • Fetal anemia is often diagnosed at a cutoff point of 10 grams per deciliter, which is also the standard therapeutic threshold.
  • Testing cord samples using a cell counter helps determine the baby's hemoglobin level. If it's below 10 grams per deciliter, treatment is required.

Exchange Transfusions and Treatment Approach

This section discusses exchange transfusions and their role in treating neonatal HDFN.

Exchange Transfusions

  • Exchange transfusions are performed after delivery to remove unconjugated bilirubin.
  • Phototherapy is the primary treatment for HDFN after delivery, so exchange transfusions are rare.
  • In exchange transfusions, small amounts of the neonate's blood are removed and replaced with prepared whole blood.
  • Prepared whole blood consists of group O red blood cells reconstituted to a hematocrit determined by the physician using AB plasma.
  • The goal is to remove unbound maternal antibodies and sensitized cells while ensuring optimal oxygen delivery.

Blood Requirements for Intrauterine and Neonatal Transfusions

This section covers the requirements for blood used in intrauterine and neonatal transfusions.

Blood Requirements

  • Blood for intrauterine and neonatal transfusions should be group O RhD negative unless otherwise determined.
  • It should be irradiated to prevent graft-versus-host disease.
  • It should be hemoglobin S negative and fresh (less than seven days old) to ensure optimal oxygen delivery.
  • Antigen negativity is important to match the mother's antibodies.

Review of Perinatal Testing Categories

This section provides a review of perinatal testing categories.

Perinatal Testing Categories

  • Perinatal testing can be categorized into three arms:
  • Arm 1: Serological incompatibility between mother and fetus leading to mild HDFN.
  • Arm 2: Testing cord cells for group compatibility, positive DAT, and absence of other antibodies. Louis Freestyle Illusion may be performed for confirmation.
  • Arm 3: Testing for unexpected antibodies or high-risk situations.

The transcript does not provide further information beyond this point.

New Section

This section discusses the different arms of perinatal testing and their importance in preventing hemolytic disease of the fetus and newborn (HDFN).

Perinatal Testing Arms

  • The first arm is based on the RHD test and involves administering Rhogam to an RHD negative mother at 28 weeks gestation, regardless of fetal blood type. This helps prevent alloimmunization.
  • The second arm focuses on assessing whether a fetal bleed is present when an RHD positive neonate is born to an RHD negative mother who has received Rhogam. If a bleed is detected, additional Rh immune globulin (RIG) needs to be given to prevent alloimmunization.
  • The third arm involves the initial maternal antibody screen. If the antibody screen is positive and a clinically significant antibody is identified, there may be a risk of HDFN.

New Section

This section explains how quantitating the fetal bleed using the Clihauer-Betke test can help determine the amount of additional RIG needed to prevent alloimmunization.

Quantitating Fetal Bleed

  • If a fetal bleed is present, it needs to be quantitated using the Clihauer-Betke test.
  • The results of this test help determine how much additional Rh immune globulin (RIG) should be given to prevent alloimmunization.

New Section

This section discusses how certain antibodies can cause HDFN and mentions some of the most lethal antibodies.

Antibodies Causing HDFN

  • Some antibodies, such as anti-D, can cause HDFN in subsequent pregnancies.
  • Anti-Kell (anti-K) is another antibody that can cause severe anemia issues.
  • Other antibodies, like anti-Big K, can also lead to serious complications and may require intrauterine transfusion.

New Section

This section explains the methods used to determine if the fetus has the antigen associated with a specific antibody.

Determining Fetal Antigen Expression

  • Testing the father's blood for the antigen is one method, but it is not commonly used.
  • Titering the antibody or using imaging techniques are more common approaches.
  • If the antibody titer increases after four weeks, it indicates exposure to the antigen and suggests that the fetus expresses it.
  • Imaging techniques such as ultrasound or Doppler of the middle cerebral artery peak systolic velocity can also be used to assess fetal antigen expression.

New Section

This section discusses when imaging techniques are typically employed and mentions performing an acid elution test after birth.

Imaging Techniques and Acid Elution Test

  • Imaging techniques like ultrasound or Doppler are often reserved for pregnancies where previous babies have been affected by HDFN due to maternal antibodies.
  • After birth, if the Direct Antiglobulin Test (DAT) is positive, an acid elution test is performed to verify the causative antibody.

New Section

This section summarizes key points covered in the presentation and emphasizes three main areas of concern in perinatal testing for HDFN.

Key Points and Areas of Concern

  • Hemolytic disease of the fetus and newborn (HDFN) occurs when a mother who has been exposed to a red blood cell antigen carries a baby expressing that same antigen. The mother's antibodies cross the placenta, leading to anemia in the fetus.
  • Medical technologists play a crucial role in performing various tests related to perinatal testing for HDFN.
  • Three main areas of concern in perinatal testing are the initial type and screen of the mother, antibody identification and titration, and assessing fetal bleed and determining additional Rh immune globulin (RIG) requirements.

New Section

This section highlights the consequences of HDFN and emphasizes the role of medical technologists in performing necessary tests.

Consequences of HDFN and Role of Medical Technologists

  • HDFN can lead to anemia in the fetus and potentially cause permanent brain damage due to the buildup of unconjugated bilirubin after delivery.
  • Medical technologists are responsible for performing tests such as initial type and screen, antibody identification, Rh typing, DAT, acid elution test, fetal bleed screen, and Clihauer-Betke test. These tests help identify potential risks and guide appropriate interventions.

Contrast between HDFN and RH HDFN

This section discusses the differences between HDFN (Hemolytic Disease of the Newborn) and RH HDFN (Rhesus Hemolytic Disease of the Newborn).

Differences between HDFN and RH HDFN

  • HDFN: Usually mild, can be treated with phototherapy, but not preventable.
  • RH HDFN: More severe, requires drastic measures for treatment such as intrauterine transfusion or exchange transfusion after delivery.
  • Preventability: RH HDFN is preventable if the mother has never been exposed to the D antigen.

Allo Antibodies in HDFN

This section explains how allo antibodies contribute to Hemolytic Disease of the Newborn.

Allo Antibodies in HDFN

  • Any clinically significant allo antibody, especially IGG ones, can cross the placenta and potentially bind to fetal cells.
  • This binding can lead to hemolytic disease in the fetus.

Use of RIG for Rh-Negative Pregnant Women

This section discusses the use of RIG (Rh immune globulin) for Rh-negative pregnant women.

Use of RIG for Rh-Negative Pregnant Women

  • RIG should be given to pregnant women who are Rh-negative and do not already have anti-D antibodies.
  • The purpose of RIG is to prevent the mother from developing anti-D antibodies if she is exposed to D-positive fetal cells during pregnancy or after delivery.
  • RIG may also be used when transfusing D-positive pooled platelets to D-negative women of childbearing age.

Tests for Detecting Fetal-Maternal Hemorrhage

This section explains two tests used to detect and quantify fetal-maternal hemorrhage.

Tests for Detecting Fetal-Maternal Hemorrhage

  • Fetal Bleed Screen (Rosette Test): Anti-D is added to the patient's RBCs to check for the presence of RhD-positive cord cells. Rosettes form around RhD-positive cord cells when indicator cells are added.
  • Kleihauer-Betke Test: Acid elution is used to lyse adult cells, and a counter stain is added. The living fetal cells take up the counter stain. The number of fetal and adult cells are counted using a Miller disc or other methods.

Calculating Fetal Bleed Percentage

This section discusses the calculation of fetal bleed percentage and determining the amount of RIG needed.

Calculating Fetal Bleed Percentage

  • After performing the Kleihauer-Betke test, calculations are done to determine the fetal bleed percentage.
  • The number of vials of RIG needed is determined based on these calculations, rounding up or down as necessary.

Blood Product Requirements for Transfusion

This section explains the requirements for blood products used in intrauterine transfusion and exchange transfusion.

Blood Product Requirements for Transfusion

  • Blood products used for intrauterine transfusion and exchange transfusion should be O Negative.
  • They should be hemoglobin S negative, CMV negative, irradiated, and less than seven days old units for exchange transfusion.