HDFN Flashcards
Anti-K HDFN
affects Kell positive precursors in the bone marrow, suppresses rather than hemolytic destroys precursors. Lab results low bilirubin and reticulocytopenia
HDN etiologies
hemolytic disease of newborn: infection, RBC membrane defects, hemolysis due to blood group incompatibility
Most efficient antibody in crossing the placenta
IgG1 (IgG3 and IgG4 also efficient) IgG2 cannot cross
Important considerations of fetal antigen
homozygous vs. heterozygous, degree of antigen expression, could affect the severity
Erythroblastosis fetalis
Anemia, depends on the ability of the fetus to increase hematopoiesis- this causes hepatosplenomegaly. causes portal hypertension and leads to hydrops fetalis
What occurs in system during hydrops fetalis
portal hypertension, edema, effusions, cardiac failure (minimum excess bilirubin-hyperbilirubinemia is not the issue)
Steps of hemoglobin breakdown in fetal/maternal situation
hemoglobin can take one of two routes: it always goes to unconjugated bilirubin, which can then go to the placenta, then to the mothers liver, is broken down to conjugated and excreted by the mother. The unconjugated bilirubin can alternatively go to the immature fetal liver which can’t break it down and it is continued as toxic unconjugated bilirubin- leads to hyperbilirubinemia, jaundice and kernicterus
kernicturus
nuclear jaundice- bilirubin deposits basal ganglia which interferes with mitochondrial function. Bilirubin builds up in babies brain
Quantity of billirubin in kernicturus
> 25mg/dl normal 8-12 mg/dl VLBW (very low birth weight)
outcome of kernicterus
high morbidity and mortality
How much blood is needed to cause immunization
0.1 mL of fetal blood
outcome of RHHDN
historically very severe anemia and death in utero- through use of RHIG significantly reduced
How does ABO incompatility offer protection against alloimmunization
16% vs. 1.5-2%
ABO HDFN hemolysis
usually mild, requiring no treatment, only in O mothers due to ABO antibodies being both IgM and IgG
Prenatal testing performed
ABORH Ab screen, weak D not required. Antibodies ignore: I, P1, Lea, Leb. Testing father for “offending” antigen
Father testing in prenatal studies
Test for antigen, if it’s heterozygous 50/50 chance child received it homo 100% chance child got it. Consider DNA testing if anti-D in mother
Genotyping fetus methods of collection
Amniocentesis, p.b. of mom, CVS (chorionic villus sampling), Cordocentesis
CVS
chorionic villus sampling, collecting from placenta where attached to uterine wall
Cordocentesis
PUBS- percutaneous umbilical blood sampling, use ultrasound to find appopriate placement
Syndromes affecting pregnant women involving blood transfusion
ITP (idiopathic thrombocytopenia) HDFN, FNAIT (fetal and neonatal alloimmune thrombocytopenia)
Earliest HDFN can occur
18-20 weeks
Half life if IgG
21-25 days
Titer considered significant in prenatal testin
> /= 16 or 32. exception is anti-K significant >/=8. There is no need to titer ABO or IgM antibodies
How do you test samples that have been frozen for titers
in duplicate
Doppler ultrasound
non invasive monitoring, measures the blood flow of MCA, increase blood flow indicated anemia- transfusion should be considered, assess hydrops fetalis
MCA
middle cerebral artery
Delta OD
change in the optical density, bilirubin present in the amniotic fluid makes it yellow and changes the optical density. Run the sample to determine OD, a linear downward line charted- compare the result read at 450 with the graph line and document the change, this is the change in the optical density
Reading the results of optical density
0.26-0.46 low risk (zone 1) 0.47-0.90 middle risk (zone 2) 0.91-1.0 High risk (zone 3)
IUT
intrauterine transfusion blood selection: irradiated hgbS negative, CMV- reduced risk, “fresh blood” antigen negative (consider using mom) compatible with mom’s plasma
Facts about IUT
hct decline 1% per day, usually required within 1-2 weeks, holds of hematopoiesis therefore holding of erythroblastosis fetalis, maintain until delivery
Other alternatives to IUT
mother plasma exchange-reduces anibody temporarily, IVIG
infant testing at birth
aborh (no reverse), perform weak D testing be aware of “Blocked D” phenomenon
DAT infant testing
may be positive with RHIG, may be negative with ABO HDN, if DAT+ and mom’s ab screen is negative, consider low incidence antigen.
Good source for antigen negative blood for baby for IUT
mother’s blood
Treatment goals HDN
prevent complication from hyperbilirubinemia (phototherapy and exchange transfusion) treat anemia (straight transfusion or exchange transfusion)
RBC requirements for transfusion of neonates
IRRadiated if <1200g. standard dose for transfusion is 10-15ml/KG
Objectives of exchange transfusion
reduce billirubin, reduce maternal antibody, correct for anemia
How much is in one vial of Rhogam and how much does it cover
1ml (300ug) clears 30ml of WB or 15mL of RBCs
Rosette test
Qualitative, detects FMH >/=10mL. infant cannot be weak D positive,must be D positive. Mother being weak D positive invalidates results
Kleihauer Betke
quantitative (kind of) poor precision and accuracy. Acid elution test- capitalizing on resistance of fetal hgb to acid treatment. Mom blood put on a slide, acid treated, rinsed and counterstained. Count 1000-2000 cells. maternal cells are “ghost cells” fetal cells are pink
Problems causing erroneous results with KB test
hereditary persistence of fetal hemoglobin disease in mother, sickle cell disease
Calculation of FMH from KB test
(Fetal cells counted/total cells counted) x mothers blood volume (5000mL typically used)
3 ways to detect FMH
KB, rosette test, flow cytometry
Positive and negative rosette test
negative and = 4 rosettes per 5 fields is negative (less than 30mLs) anything more than that is positive
Additional indications for RHIG
PUBS, Amniocentesis, miscarriage/abortion, CVS, ectopic pregnancy, antepartum bleeding (abdominal trauma, placental abruption, threatened abortion) any other condition that would be a risk of fetal RBCs entering mothers circulation
Alloimmune thrombocytopenia
most common antibody implicated is anti-HPA-1a, antigen present in 98% of population, can affect first pregnancy not known until delivery- potential of intracranial hemorrhage
Treatment for mom in future pregnancies
determine fetal DNA genotype, IVIG for mom, transfuse HPA-1a negative platelets (can use mom, however must be washed (due to antibody))
VLBW
very low birth weight
which tends to be more severe: thrombocytopenia from SLE or from ITP (maternal)
ITP
Volume of fetal cells calculation
(#fetal cells/#of maternal cells)(5000mL) = mL of fetal blood
Prenatal titers saline AHG vs. albumin
recommendation is saline AHG, albumin AHG (or gel) results typically in higher titers.
Most common types of ABO-HDFN
European ancestry and asians- Type A babies type O moms, Blacks- Type B babies type O moms
High MCA result
> 1.5 MoM (multiples of the mean) indicates moderate to severe anemia
Why does it need to be HGbS negative
prevent sicking under low oxygen tension
typical hematocrit of concentrated RBC unit requested for neonates
70-85%
what do you need to do if using mother’s blood for IUT
wash and irradiate
calculation volume of blood to be transfused
(estimated fetal weight (g) multiplied by 0.14mL standard factor) x (goal hct-current hct) / (hct of the rbc unit to be transfused)
Where is the IUT transfused into
umbilical cord artery
second choice for location of IUT
peritoneal cavity
what does IVIG treatment do in mother with antibody (HDFN)
stabilized anti-D titers- best if used before 28 weeks
What does plasma exchange of mother with anti-D do?
Drops antibody levels by 75%
What does phototherapy do?
Oxidizes unconjugated bilirubin allows for release from system
How is RHIG made?
human pooled plasma from individuals naturally immunized or intentionally immunized.
Chance of an RH mother being immunized to Rh
16%
Chance of an RH mother being immunized to Rh after administration of RHIG
<0.1%
Relevance of anti-G in pregnancy
it’s important to differentiate anti-G from anti-D and anti-C, if anti-G is present mother still gets RHIG, if they are immunized to Rh with anti-D present, they don’t receive RHIG
RHIGs role in vivo
D pos RBC- opsonized by the RHIG IgG cleared by macrophages in the spleen
Weak D
european ancestry most common types 1,2,3 don’t need RHIG any other type of weak D should be given RHIG and considered D negative due to lack of understanding about other weak D types to become alloimmunized.
Risks of IUT
Donor blood further alloimmunization of the mother to new antigens. Providing RBC matched: Rh, K Fy, Jk, S- decreases immunization by 60%. You can use mother’s blood but it must be washed.
FNAIT antibodies cause.
Fetal, neonatal alloimmune thrombocytopenia. 80% of european cases caused by anti-HPA-1a antibody. (HPA-1a present in 98% of population). 10% Anti-HPA-5b 4% Ant-HPA-2b 2% Anti-Hpa-3a. In asians anti-HPA-4b is the most common
Signs and symptoms of FNAIT in babies
GI bleeding, petechiae, ecchymoses, ICH
Treatment/Prevention of FNAIT
IVIG administration in mom- effective in nearly 100% (success is measured by absence of ICH)
ITP in neonates
immune thrombocytopenia. Baby may be thrombocytopenic if mother has ITP or SLE- antibodies cross the placenta and cause the same problems in the baby as they did in the mom, once the maternal antibodies are gone the platelet count should go back to normal
Sequalae
any abnormality following a disease or treatment or surgery
Which is more severe ITP or FNAIT?
FNAIT is much more severe. In ITP only 0-1.5% ICH, even less severe if due to maternal SLE than ITP
Treatment of ITP in neonates
IVIG, corticosteroids for mom. In baby: ultrasound of brain looking for ICH - if life threatening hemorrhage should be treated with platelets and maybe IVIG/steroids
What is a VLBW baby
<1500g
Extremely low birth baby
<1000g
Premature baby hgb compared to full term neonate
premature= 1 g/dL lower hgb than normal; Hgb usually drops following birth post birth drops to 8/7 g/dL
Why does Hgb drop in baby (3 reasons)
- EPO decrease (prolonged in premature babies) -decreased RBC production 2. Decreased survival of fetal cells 3.Increasing blood volume due to rapid growth. decrease EPO, increase 2,3 DPG, PO2 and HgbA.
EPO production- where does it take place
Originally liver production of EPO, however once born it switches to kidney based production of EPO
AABB standars for how frequently to test babies blood type
Due to infants inability to make antibodies, no repeat of ABORH or ABscreen testing needs to be done during the initial 4 month period of the baby in hospital.
ECMO
extracorporeal membrane oxygenation. a machine that removes blood from patients venous ciruclation, the blood is circulated through a machine that removes CO2 and replaces O2 and then is returned to the patient.
Necrotizing entercolitis
ischemic necrosis of intestinal mucosal associated with inflammation, invasion of enteric gas forming organisms and dissection of gas into abdominal cavity
SCI
silent cerebral infarcts;
ECMO and platelets
ECMO circuit consumes platelets higher platelet counts are maintained.
what is the least invasive method for retrieval of fetal cells for genetic testing
probably mother’s p.b. with free floating baby DNA, however if not at a high enough quantity amniocentesis is the next option (cell-free fetal DNA typically at high enough quantity at 15 weeks)
