Blood Bank: HDFN

Erythroblastosis fetalis

During HDFN, accelerated RBC destruction results in the fetus increasing RBC production, therefore, there are increased numbers of nucleated RBCs. The condition where maternal Abs destroy fetal RBCs is called…

Hydrops fetalis

Severe cases of HDFN can result in a condition called (——), which is severe anemia that can lead to generalized edema, cardiovascular failure, and tissue hypoxia, both of which can lead to fetal death

• In-utero (prepartum)

• Postpartum (ex-utero)

2 stages of HDFN

• RBC destruction → severe anemia

• Edema

• Heart failure

• Fetal death

Dangers of in-utero HDFN (4)

Kernicterus (bilirubin encephalopathy)

In-utero, hyperbilirubinemia in the fetus does not occur because the mother’s liver conjugates the bilirubin. On the other hand, in ex-utero HDFN unconjugated bilirubin can build up to toxic levels, leading to…

• ABO

• Rh

HDFN is most commonly caused by (——), but the most severe form of HDFN is caused by (——)

• Subsequent pregnancy?

• Previous transfusion?

• Type and screen (ABS (-) → repeat 24 wk)

Relevant maternal history that would help identify the risk of HDFN (3)

• Identify Ab

• Perform titration if significant

• Freeze serum (for future titer parallel testing)

  • Two tube increase is significant

What testing is performed when a maternal ABS is positive? (3)

1st

ABO HDFN can occur during the (——) pregnancy

Anti-A,B

While anti-A and anti-B are IgM Abs and cannot cross the placental barrier, (——) in type O mothers can cross the placenta and cause HDFN

• Jaundice 12-48 hrs after birth

• Microspherocytes

• ABO, Rh, and DAT on cord blood

• Elution against A cells, B cells, Ab screen cells (when DAT+)

What features help diagnose ABO HDFN (4)

Middle Cerebral Artery (MCA) Peak Systolic Velocity (PSV)

At about 16-20 weeks gestation, the clinical diagnosis of anemia can be made using an ultrasonic technique called (——) which makes measurements based on the reduced blood viscosity at lower hematocrits, which results in faster velocity of the blood

450 nm

Bilirubin has an optical density reading of…

Amniocentesis

An invasive procedure performed on the mother when HDFN is suspected. The amniotic fluid is tested by measuring the optical density of bilirubin between the observed density and an extrapolated baseline (replaced by MCA-PSV)

• Zone 1 = fetal stress

• Zone 2 = Moderate disease

• Zone 3 = Severe problems

What do the different zones of the Liley graph represent? (3)

• MCA-PSV > 1.5 MoM

• Fetal hydrops (ultrasound)

• Hb < 10g/dL by cordocentesis

• Amniotic fluid ΔOD high

An intrauterine transfusion is done when… (4)

fetal Hb > 10 g/dL

The goal of intrauterine transfusion is to maintain (——) by accessing the fetal umbilical vein and injecting donor RBCs directly into the vein

• CPDA1/Adsol (nutricel) O neg RBCs (75-80% HCT)

• Hb S neg (hypoxic environment → sicking crisis)

• CMV neg (or LR-RBCs/CMV safe - not tested for CMV)

• Irradiated (avoids WBC proliferation and GVHD)

• Leukoreduced

• Ag neg for maternal Abs

Requirements of RBC blood components in an intrauterine transfusion (6)

AB FFP

Requirement of plasma components in an intrauterine transfusion

• Intraperitoneal (→ fetal abdomen)

• Intravascular (→ umbilical vein)

• Combination (avoid peaks and troughs of fetal Hct)

Transfusion methods for intrauterine transfusion (3)

• Lethicin-Sphingomyelin

• >2:1

If induced labor is considered, a (——) ratio must be performed prior to surgery to ensure the baby has mature lungs and is ready for life ex-utero; the ratio must be (——)

• Anemia

• Hyperbilirubinemia → Jaundice/Kernicterus

• BIND (Bilirubin induced neurologic dysfunction; severe retardation)

• Heart failure

• Death

Dangers of postpartum HDFN (5)

• Cutting the cord and draining to specimen tube

• Percutaneous Umbilical Blood Sampling (PUBC)

Once the baby has been delivered, cordblood is obtained via… (2)

• Bilirubin normal, no anemia

• Phototherapy

• Rare

• None

ABO HDFN characteristics (bilirubin level, anemia, treatment, exchange transfusion, intrauterine transfusion)

• Bilirubin elevated, anemia present

• Adjunct to exchange

• Common

• Sometimes

Rh HDFN characteristics (bilirubin, anemia, phototherapy, exchange transfusion, intrauterine transfusion)

• Bilirubin ≥ 20 mg/dL

• Bilirubin ≥ 20 mg/dL, Hb < 10 g/dL

In postpartum treatments for HDFN, phototherapy is done when (——) while exchange transfusion is considered when (——)

460-490 nm

In phototherapy, light at (——) is used to conjugate bilirubin and reduce jaundice

Suppression of immune system to prevent development of anti-D

• RhIG anti-D bind to fetal Rh+ RBCs

• Spleen captures fetal RBCs by Fc receptors

• Suppressor T cell response stimulated

• Spleen removes fetal RBC prior to contact with Ag presenting cells

How does RhIG work? (4)*

• Abortion or miscarriage

• 12 weeks gestation/antepartum

• 50 µg anti-D protects against 2.5 mL RBCs or 5 mL WB

RhIG microdose characteristics (indications, time of administration, dose size and protection)

• Amniocentesis/cordocentesis, abdominal trauma, antepartum hemorrhage, postpartum

• Abortion/miscarriage → 12 weeks, Antepartum → 28 weeks, postpartum → 72 hours

• 300 µg anti-D → 15 mL RBC or 30 mL WB

RhIG full dose characteristics (indications, time of administration, dose size and protection)

(Fetal cell vol from KB test / 30) + 1= # syringe

Calculation for how much RhIG to give

• Add anti-D to maternal RBCs and incubate 37C

• Wash cells and add R2R2 indicator cells (will rosette around anti-D attached to Rh pos RBC)

• Centrifuge, re-suspend. and read for rosettes

  • None → 1 vial RhIG

  • Present → Kleihauer-Betke

Describe the rosette test procedure (3)

1. Make smear of postpartum maternal blood

2. Flood smear with acid solution

3. Rinse slide and counterstain with Safranin

4. Count number of pink Hb F cells within 2,000 adult RBCs

Describe the Kleihauer Betke procedure (4)

(# fetal cells) * (maternal blood volume mL) / (2000 adult cells) = fetal bleed volume

• Maternal blood volume typically 5L (5000 mL)

Describe the fetal bleed volume calculation involved in the KB test

WinRho

A pharmaceutical drug used to treat an accidental transfusion of an Rh neg pt with Rh pos RBCs (IM injection of RhIG is not acceptable when the blood volume is larger than 30 mLs)

• Immune Thrombocytopenic Purpura (ITP)

• Pt is Rh pos and does not have splenectomy

RhIG can be used as a substitute treatment for people with (——) as it coats red cells with IgG and allows red cells to serve as decoys for splenic macrophages; this treatment has the requirements that (—2—); pt will have hemolytic anemia