PTN - Transfusion Medicine (Squires) Flashcards
What are the two types of donor recruitment and which of these is less likely to transmit infectious disease?
Volunteer and paid donors
Volunteer donors less likely to pass on infectious diseases in blood because no incentive to give other than to do good.
True or False: Volunteerism contributes to very occasional blood shortages.
True
What 4 components of the medical history of a donor are assessed during the donor screening phase of blood components?
- Blood pressure
- Heart rate
- Cardiac disease
- History/exposure to certain infectious diseases (hepatitis, HIV, etc.)
BP and HR are taken to ensure that the patient is healthy enough to handle the physical effects of donating blood.
What are the three types of blood collection?
- Allogeneic
- Directed
- Autologous
What is a directed donation?
Intended recipient of transfusion, or physician, selects a specific donor
What is an allogeneic donation?
Routine community blood donation
What are the 6 blood components?
- Whole blood
- Red blood cells
- Platelets
- Frozen Plasma
- Cryoprecipitate
- Granulocytes
What 2 types of tests are performed on donor blood to ensure that the recipient does not suffer any consequences of a transfusion?
- Blood typing and blood group antibodies - ABO and Rh antigen
- Infectious disease testing - HIV, Hep B/C, syphillis, HTLV, West Nile virus, etc.
What is apheresis donation?
Apheresis uses a machine to collect specific components while the remainder of the blood is returned to the donor.
Allows donors to only donate plasma, platelets, or RBCs.
How are whole blood donations separated into various components?
Centrifugation
Separates whole blood into plasma (cryoprecipitate), buffy coat (with WBCs and platelets), and erythrocytes
What 3 blood components are prepared using apheresis?
- Platelets
- Frozen plasma
- Granulocytes
What 4 blood components are isolated from whole blood?
- Red blood cells
- Whole blood derived platelets
- Frozen plasma
- Cryoprecipitate
What are the 4 types of factor concentrates that are commercially available?
- Factor VIII
- Factor IX
- Factor VIIa
- Prothrombin complex concentrate (PCC) - factors II, VII, IX, and X (vitamin K dependent factors)
What two molecules make up the B antigen on type B RBCs?
Fucose and D-galactose
Remember that type O blood only has fucose.
Type A has fucose and N-acetylgalactosamine
When ABO typing, what 2 blood components must be tested?
- Red blood cells - antigens
- Plasma - plasma antibodies
What is reverse typing of blood?
Reverse typing occurs when the patient’s serum is tested for anti-A or anti-B antibodies.
Patient serum mixed with commercial A or B RBCs to see if reaction occurs
What is typing discrepancy?
When the forward and reverse typing do not agree.
What is Bombay Blood Type and is it possible for a person with this blood type to receive a transfusion?
Bombay phenotype is an autosomal recessive inheritance that results in lack of H antigen.
Anti-H antigen forms, which mounts attack against types A, B, and O blood, leading to hemolysis.
Only other bombay blood can be used in transfusion.
What are the 3 most critical Rh blood groups?
- D antigen
- E antigen
- C antigen
A patient with RBCs that test positive for anti-A and anti-D has what type of blood?
A+
How are anti-D antibodies formed in an Rh negative individual?
Anti-D IgG antibodies develop when an Rh negative individual is exposed to Rh positive blood
2 ways:
Pregnancy and transfusion with Rh positive blood
What is the Rh null phenotype and what Rh type do these individuals test as.
Rh null phenotype is characterized by no Rh antigens at all.
Typing of these individuals will lead to Rh negative result.
Hemolytic anemia and elevated bilirubin indicate Rh null
Which two blood products do not require the donor and recipient to be an ABO match?
Platelets and cryoprecipitate
What two pre-transfusion tests need to be done before blood components are selected and administered?
- ABO and Rh testing
- Serum antibody testing
Which two blood products should be given as Rh negative to women of child-bearing years? Why?
Platelets and Granulocytes
Women in their child bearing years who happen to be Rh negative could develop anti-D antibodies if given Rh positive blood. This could lead to complications if she were to get pregnant.
What two surface markers on RBCs does a direct antiglobulin (direct Coomb’s) test?
C3d and IgG
What are 4 clinical conditions associated with a positive direct Coomb’s test?
- Hemolytic transfusion reactions - from transfusion with incorrect type blood
- Hemolytic disease of the fetus/newborn - maternal IgG crosses placenta and sensitizes fetal RBCs
- Autoimmune hemolysis - IgG or IgM from autoimmune diseases
- Drug-induced autoantibodies - heparin, etc.
What are some of the risks associated with transfusion?
- Iron overload
- Alloimmunization - developing antibodies to red blood cell membranes
- Transfusion-transmitted infections
What is the expected response of hemoglobin levels in an averaged-size, non-bleeding patient who undergoes a red blood cell transfusion?
Hemoglobin should increase by 1 g/dL (or hematocrit by 3%)
What is the typical dosage of RBCs given to patients who undergo transfusions?
1 unit of red blood cells to the average-sized adult
What is the typical dosage of RBCs in pediatric patients undergoing a transfusion?
5-20 mL/kg
What are the 3 main goals of transfusion therapy for sickle cell patients?
- Improve oxygen-carrying capacity
- Decrease blood viscosity to improve blood flow
- Suppress endogenous erythropoiesis
How do blood transfusions decrease the amount of HbS in circulation?
Blood transfusions decrease the level of erythropoietin made by the kidneys, decreasing the amount of HbS in circulation.
Name the 3 types of transfusion protocols for sickle cell patients.
- Acute Simple Transfusion
- Chronic Transfusion
- Exchange Transfusion
What is an acute simple transfusion and what is it useful for?
1-2 unit red cell transfusion
Helps to alleviate symptoms:
acute anemia, acute chest syndrome, aplastic crisis, sequestration
Which type of transfusion uses apheresis to remove patient’s red cells and replace them with normal non-sickling red cells?
Exchange Transfusion
Used to rapidly adjust hemoglobin level and replace HbS with HbA
What is a chronic transfusion?
Ongoing, planned transfusions (every few weeks) even in the absence of symptoms
Used in: recurrent stroke, frequent painful crises, complicated pregnancy
How can frequent transfusions lead to iron overload?
Each RBC has 250 mg iron, but only 1 mg iron is excreted per day.
Excess RBCs get broken down and iron can’t be excreted fast enough, so it gets stored as ferritin and hemosiderin
How does iron overload lead to organ damage?
Excess iron gets deposited into cells of organs as hemosiderin or ferritin. Damage to the RES, liver, heart, and spleen are all very common in iron overload.
How is iron overload treated?
Chelation therapy
What are 3 non-immune causes of patients refractory to platelet transfusion?
- Splenomegaly - spleen takes up and traps excess platelets and becomes larger
- Sepsis/fever
- Certain Medications
True or False: HLA or platelet-specific antibodies (HPA) are responsible for causing patients to be immune-mediated refractory to platelet transfusion?
True
Transfuse HLA-matched platelet products next time
What is the name of the disease that is characterized by an incompatibility between maternal and fetal red blood cells?
Hemolytic Disease of the Fetus and Newborn
What are the two defining symptoms of hemolytic disease of the newborn?
Hyperbillirubinemia and anemia
Excess RBC breakdown leads to anemia and an excess of bilirubin in the blood.
How do the maternal IgG antibodies that attack fetal red cells get to the fetus from the mother’s circulation?
They cross through the placenta
True or False: 60% of cases of hemolytic disease of the newborn are caused by ABO incompatibility between fetus and mother.
True
Most commonly: mother has type O blood (with anti-A and anti-B), but the fetus has type A or B
What is immune-antibody hemolytic disease of the newborn and what is the most common immune antibody involved?
HDFN caused by immune antibodies to blood antigens other than ABO.
Most common antibody involved is anti-D
Generally affects 2nd pregnancy and beyond
What are the 2 ways that a mother can develop immune antibodies to certain blood antigens?
- Rh negative blood, but transfused with Rh positive blood
- Maternal-fetal hemorrhage during a previous pregnancy
Anti-D is formed and can cross the placenta, which can then attack the fetal RBCs.
What is erythroblastosis fetalis?
Prenatal presentation of HDFN characterized by anemia, high-output heart failure, edema, and polyhydramnios (hydrops fetalis)
What are the signs and symptoms of postnatal presentation of hemolytic disease of the newborn (HDFN)?
- Anemia
- Hyperbilirubinemia
- Kernicterus - bilirubin builds up to toxic levels and gets deposited in the brain
- Neonatal demise due to severe neurological complications
How does Rh Immune globulin (RhIg) prevent the development of anti-D in Rh negative mothers?
RhIg is an antibody to D antigen
RhIg binds D antigen on fetal cells and removes them before they can get to the mom’s cells. This prevents anti-D from forming.
What two tests are available at delivery to assess fetal-maternal hemorrhage greater than 30 mL?
- Rosette Test - only tells you if bleed is large or small
- Kliehauer-Betke Test - determines how many doses of RhIg are necessary
RhIg prevents the formation of anti-D for maternal-fetal hemorrhages below 30 mL.
If a mother tests positive for anti-D antibodies, what should be done next?
- Identify the antibody through screening
- Do a titer of the specific antibody (IgG or IgM)
- IgG can cross placenta, but IgM can’t
- Higher titer = more severe
- If IgG –> evaluate fetus with amnio or doppler
What is the critical titer for HDFN that indicates that an amnio or other test to assess the status of the fetus should be done?
8 to 16 (aka Dilution of 1:8 to 1:16)
Status of fetus should be assessed if critical titer is reached
Which specific compound in the amniotic fluid is measured via amniocentesis when HDFN is suspected?
Bilirubin
The more bilirubin in the amniotic fluid, the more severe the HDFN is
You are assessing your pregnant patient for the presence of a maternal-fetal hemorrhage and find that a bleed larger than 30 mL has occurred. You order an amniocentesis and the results put the fetus in zone 1. What does zone 1 indicate about how much effect the bleed has on the fetus?
Zone 1 indicates a mildly affected fetus
Zone 3 indicates a severely affected fetus.
Zone 2 is questionable
What is a middle cerebral artery peak systolic velocity (MCAPSV)?
A non-invasive doppler study of the MCA of the fetus. This correllates with moderate to severe fetal anemia.
Most useful between 18 and 35 weeks
True or False: If a fetus is thought to be severely affected by HDFN, an intrauterine transfusion can be performed to increase hemoglobin.
True
Must know blood antigen and give anti-Kel/D, etc. with transfusion. Always use O negative blood that is irradiated.
What are 2 management options for the postnatal period of HDFN?
- Phototherapy - fluorescent light used to breakdown bilirubin so it can be excreted
- Exchange transfusion - removes bilirubin, antibody-coated RBCs and maternal antibodies
What are the indications for an exchange transfusion?
- Cord hemoglobin < 10 g/dL
- Rapidly rising bilirubin (>0.5 mg/dL/hour)
- Bilirubin > 20 mg/dL in term infant
- Lower in premature, hypoxia, acidosis, hypothermia
