Transcript Hemolytic Disease of the Newborn, Current Methods of Diagnosis

Unit 11 Neonatal and
Obstetrical Transfusion
Practice – Part 3
Terry Kotrla, MS, MT(ASCP)BB
Exchange Transfusion
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Used most often for HDFN but has recently
been used to treat RDS, DIC and sepsis.
Mortality rate 1%,may be substantial
morbidity.
Quantified (i.e. 2 volume, single volume) to
reflect affect on infant’s total blood volume.
Depends on bilirubin levels, amount and rate
of increase.
Exchange Transfusion
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Immediate effectiveness of a two-volume exchange
transfusion is 45-50%.
Plasma bilirubin tends to rise or rebound after an exchange
transfusion because:
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entry of bilirubin from the extravascular spaces and tissues
continued production of bilirubin from residual maternal antibody
coating newly released RBCs.
Additional exchanges are necessary if the bilirubin level
threatens to exceed 20 mg/dL in a full term infant.
Phototherapy is used as an adjunct
Exchange Transfusion
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Infant severely affected with HDFN will require
exchange transfusion.
Goals – MEMORIZE
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Reduce the load of accumulated bilirubin
Reduce the amount of unbound maternal antibody.
Remove antibody coated cells, whose destruction would
further raise the bilirubin load.
Replace infant cells with RBCs compatible with the
maternal antibody, which will have a normal survival rate.
Replacement with donor plasma restores albumin and any
needed coagulation factors.
Compatibility Testing for Exchange
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Donor blood
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Serum or plasma of infant or mother may be used for
crossmatch, mother best as
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Usually O negative,
lacks all antigens to which mom has antibodies
Coomb’s crossmatch compatible.
larger quantity available and
has highest concentration of antibody.
Blood must be compatible with baby AND mom.
Compatibility Testing for Exchange
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Mom’s blood not available:
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Use eluate from cells which concentrates
antibody, serum may have lower concentration.
Use of infant’s serum or eluate not ideal but
preferable to delaying the transfusion.
Selection and Preparation of Blood
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Selection
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CPD, as fresh as possible, preferably <5 days old.
Hematocrit of 80% or greater to minimize volume overload.
Volume transfused ranges from 75-175 mL depending on the fetal
size and age.
CMV negative
Hemoglobin S negative
IRRADIATED
Preparation
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Physician will specify a hematocrit.
Reconstitute donor unit with plasma.
Most facilities prefer to use group O red cells and AB plasma.
Exchange Transfusion
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Cannulate umbilical vein.
“Pull” baby blood.
Wait
“Push” donor blood.
Wait
Repeat
Rh Immune Globulin
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Concentrated solution of IgG anti-D from
human plasma.
A 1 mL FULL dose contains 300 ug of anti-D
to counteract immunizing effects of:
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15 mLs D pos packed RBCs
30 mLs D pos whole blood
Does NOT transmit hepatitis or HIV
Rh Immune Globulin
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Used to protect D negative individuals
exposed to D positive rbcs.
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Prenatally to D neg moms
Postnatally when D neg gives birth to D pos
After transfusion of D neg with blood products
with D pos rbcs.
The IgG anti-D coats D pos rbcs causing their
destruction before being recognized.
HDFN
Rh Immune Globulin
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Became available in 1968.
Major breakthrough.
Immunization to D antigen from 8% during
first pregnancy and additional 8% during
second pregnancy to 1-2&
Antepartum Rh Immune Globulin
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Discovered that D neg women given RhIg
after birth of D pos child still developing antiD – termed “RhIg failures”
Discovered that immunization decreased from
1% to less than 0.1% if dose given at 28
weeks.
Rh Immune Globulin
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Testing at delivery:
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ABO/D type to identify D negative mothers.
Antibody screen to detect immune antibodies.
ABO/D type of cord blood.
Women Who are NOT RhIg Candidates
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D negative women with D negative babies.
D positive women
D negative women immunized to the D
antigen.
Evaluation of Anti-D in Postpartum Specimen
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Women who receive antenatal RhIg may have
positive antibody screen.
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History IMPORTANT
RhIg given at 28 weeks WEAKLY reactive if
delivery is full term.
Do NOT assume antibody is immune.
When in doubt give it out.
Evaluation of Anti-D in Postpartum Specimen
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Clues to distinguish origin of antibody
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RhIg is IgG, if anti-D is saline reactive probably
represents active immunization.
RhIg rarely achieves titer above 4, high titer antiD is immune.
Obtain confirmation from physician records.
Administer RhIg if there is any doubt.
Administration of RhIg
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Antepartum dose given at 28-30 weeks
gestation, 92% of women who develop anti-D
do so at 28 weeks or later.
Obtain blood sample BEFORE administering.
Perform T&S
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Must be D and weak D negative
Identify antibodies if screen positive, if antibody
other than anti-D give RhIg
Administration of RhIg
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RhIg anti-D may be detectable for as long as 6
months.
Half live is 23 days, 300 ug given at 28 weeks, 20-30
ug present at delivery 12 weeks later.
Inject within 72 hours of delivery.
Do not delay or omit injection due to problems with
antibody screen interpretation.
If RhIg NOT given within 72 hours give as soon as
possible, do not withhold!!!
RhIg Utilization Gap
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Administration of RhIG is indicated, but sometimes
inadvertently omitted, after several common events
(MEMORIZE):
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abortion/miscarriage
ectopic pregnancy
antepartum hemorrhage
fetal death
amniocentesis
chorionic villus sampling
cordocentesis
After an external cephalic version of a breech fetus
blunt trauma to the abdomen
Detection of Fetomaternal Hemorrhage
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Immunization to D can occur if amount of
fetal rbcs entering maternal circulation
exceeds 30 mLs of whole blood, the amount
covered by a single 300 ug dose of RhIg.
Risk of hemorrhage exceeding 30 mLs
estimated to be 0.3%.
Standards requires that post-partum maternal
sample be evaluated for excessive bleed.
Detection of Fetomaternal Hemorrhage
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Weak D test was used for screening for
excessive fetomaternal hemorrhage (FMH).
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Fetal D pos rbcs would be coated by the reagent
anti-D
Microscopic evaluation of the weak D reveals
small, tight clumps of rbcs, MF agglutination
Very insensitive test and requires skill.
CAP survey 12% of labs failed to detect D pos
cells in sample simulating 30 mL bleed.
Rosette Screening Test
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Similar to weak D, drop of maternal rbcs incubated with antiD which coats D antigens of fetal rbcs present.
Wash off anti-D.
Add D pos indicator rbcs which will bind to second Fab of
the anti-D coating the cells.
Forms rosettes around the cells.
Detects FHM of approximately 10 mLs
Qualitative test only, if positive must perform Kleihauer
Betke acid elution test to quantitate.
IMPORTANT: If baby types weak D positive a Kleihauer
Betke MUST be done instead of the Rosette.
Kleihauer-Betke Acid Elution
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Hemoglobin F is resistant to acid elution,
adult hemoglobin is not.
Expose thin smear of blood to acid buffer,
adult hemoglobin eluted out.
Smears are stained with hematoxylin and
erythrosin B.
Kleihauer-Betke Acid Elution
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Adult rbcs appear as ghost cells, stroma only, while fetal
cells appear bright pink and refractile.
Count number of fetal cells in 2000 adult cells.
Precision of test poor even in experienced hands.
Kleihauer-Betke Acid Elution
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To calculate volume of fetomaternal
hemorrhage:
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Determine percentage of fetal rbcs.
Multiply x 50 (represents 5000 mL, arbitrary
blood volume of mother).
Divide by 30, volume of whole blood covered by
1 vial of RhIg, to determine number of vials
required.
Round up or down and ADD 1 VIAL for safety.
Kleihauer-Betke Acid Elution
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EXAMPLE
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26 fetal cells counted in 2000 total.
26/2000= 1.3%
1.3 x 50 = 65 mL of fetal whole blood
65/30 = 2.2 doses of RhIg
2.2+ 1(safety dose) = 3 vials
You will be required to calculate for the next
exam.
Giving RhIg
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Given intramuscularly.
No more than 5 doses should be injected at
one time.
If more than 5 doses needed space over 72
hours.
Kleihauer-Betke Acid Elution
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False positive may occur if patient has
persistent presence of hemoglobin F due to
certain diseases: sickle cell anemia,
thalassemia, acquired aplastic anemia, and
several other hemoglobinopathies.
The amount of hemoglobin F in these
conditions varies in the cell so the staining is
not uniform.
Flow Cytometry
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Uses anti-hemoglobin F antibodies to bind,
followed by incubation with labeled antiantibody.
Counted in flow cytometer.
End of Unit 11Part 3