Unit 11 Neonatal and Obstetrical Transfusion Practice – Part 3

Terry Kotrla, MS, MT(ASCP)BB

Exchange Transfusion 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 Immediate effectiveness of a two-volume exchange

transfusion is 45-50%. Plasma bilirubin tends to rise or rebound after an exchange

transfusion because: 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 Infant severely affected with HDFN will require

exchange transfusion. Goals – MEMORIZE

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 Donor blood

Usually O negative, lacks all antigens to which mom has antibodies Coomb’s crossmatch compatible.

Serum or plasma of infant or mother may be used for crossmatch, mother best as larger quantity available and has highest concentration of antibody.

Blood must be compatible with baby AND mom.

Compatibility Testing for Exchange Mom’s blood not available:

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 Selection

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 Physician will specify a hematocrit. Reconstitute donor unit with plasma. Most facilities prefer to use group O red cells and AB plasma.

Exchange Transfusion

Cannulate umbilical vein. “Pull” baby blood. Wait “Push” donor blood. Wait Repeat

Rh Immune Globulin 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: 15 mLs D pos packed RBCs 30 mLs D pos whole blood

Does NOT transmit hepatitis or HIV

Rh Immune Globulin Used to protect D negative individuals

exposed to D positive rbcs. 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 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 Discovered that D neg women given RhIg

after birth of D pos child still developing anti-D – termed “RhIg failures”

Discovered that immunization decreased from 1% to less than 0.1% if dose given at 28 weeks.

Rh Immune Globulin Testing at delivery:

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

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

Women who receive antenatal RhIg may have positive antibody screen. 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

Clues to distinguish origin of antibody RhIg is IgG, if anti-D is saline reactive probably

represents active immunization. RhIg rarely achieves titer above 4, high titer anti-

D is immune. Obtain confirmation from physician records. Administer RhIg if there is any doubt.

Administration of RhIg 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

Must be D and weak D negative Identify antibodies if screen positive, if antibody

other than anti-D give RhIg

Administration of RhIg 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 Administration of RhIG is indicated, but sometimes

inadvertently omitted, after several common events (MEMORIZE): 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 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 Weak D test was used for screening for

excessive fetomaternal hemorrhage (FMH). 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 Similar to weak D, drop of maternal rbcs incubated with anti-

D 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 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

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 To calculate volume of fetomaternal

hemorrhage: 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 EXAMPLE

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 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 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 Uses anti-hemoglobin F antibodies to bind,

followed by incubation with labeled anti-antibody.

Counted in flow cytometer.

End of Unit 11Part 3