Blood Transfusion Seminars Flashcards Preview

General Med 1 > Blood Transfusion Seminars > Flashcards

Flashcards in Blood Transfusion Seminars Deck (26):
1

What are the types of blood donations you can give?

1. whole blood
2. apheresis:
- platelets
- plasma
- plasma and platelets
- double red cell

2

What are the requirements?

- healthy
- 16-70
- >50kg
- no recent pregnancy, IV drug use or overseas travel

3

What are the rejection criteria?

- heart condition
- pregnancy
- anaemia
- tattoos
- iv drug use
- risky sexual behavior
- UK between certain dates (mad cow)

4

What are the components of blood?

Red blood (leucodepleted to avoid adverse reactions)

Plasma products:
- cryoprecipitate
- cryodepleted plasma (minus clotting factors)

Buffy coat:
- white blood cells
- platelets

5

Why do we only worry about the recipients antibodies, and not the donors?

Anti-A and Anti-B antibodies from donor are in the plasma fraction, so separating blood allows to separate red blood from antibodies, which means O can go to A, B and AB. We only have to worry about antibodies in recipient.

6

What are plasma products used for?

Low platelet count or dysfunctional platelets can lead to increased risk of bleeding, I,e, due to chemo.
Fresh frozen plasma used to replace missing or low levels of proteins in blood.
Cryoprecipitate contains clotting factors, so used with clotting disorders.

7

What storage is required for blood?

- RBCs in fridge for 42 days
- Platelets at room temp for 5 days
- Fresh frozen plasma below -25 for 12 months.
SO ALWAYS check the best before date.

8

How is AB status checked?

1. forward grouping – take patients RBC’s and mix them with anti-serum which will react with antigens present on the RBCs. Determines directly what antigens are present on your RBCs.

2. reverse grouping – take the patients plasma and mix it with commercial RBC’s to see what antibodies are in the patient’s plasma. Determines antigens INDIRECTLY by working out what antibodies are present.

9

How is RhD status determined?

Only forward typing.
Patient blood mixed with anti-D serum which contains antibodies against RhD.
- positive – agglutination observed
- negative – pellet observed

10

What is the Gel-column technique?

Gel-column technique, which can do both forward and reverse grouping. RBCs will either float or sink. RBC’s can travel down the column, which is Swiss cheese like. But they can’t if there is agglutination, therefore they will stay at the top.

If control is at top, then the test is useless because it would be agglutinating regardless of exposure.

11

What is a crossmatch?

Mix RBCs from donor with the patient’s serum from the actual bag you are going to use, and there should be no haemolysis or aggulation or you might kill them.
1. Abbreviated crossmatch
2. Antiglobulin crossmatch – can detect the actual immune response specifically

If you don’t have time to check, best is O- and just hope for the best.

12

What is an adverse event in relation to a transfusion?

1. Mild – itching, fever, hives and rash – easily treated
2. Severe – breathing difficulties, high fever, shaking, low BP, dark urine, aches and pains.

13

How are adverse events classified?

Classification:
- Immunological or non-immunological
- Acute (24 hrs) or delayed

a) Acute Immunological:
- hemolytic transfusion reactions
- febrile non-hemolytic transfusion reactions
- allergic reactions (i.e. hives)
- transfusion-relation acute lung injury
b) Acute Non-Immunological:
- cardiac overload
- sepsis
- massive transfusion complications
- non immune mediate haemolysis (physical/chemical destruction of blood)
c) Delayed Immunological:
- formation of alloimmune red cell antibodies
- delayed haemolytic transfusion reaction
d) Delayed Non-Immunilogical:
- iron overload
- fever
- jaundice
- lower than expected haemoglobin

14

What are the most common adverse events?

- fever
- chills
- urticarial (hives)

15

What are the most serious adverse events?

- acute haemolytic transfusion reactions
- delayed haemolytic transfusion reactions
- bacterial contaminants of blood products

16

What are the contributing factors to an adverse event?

- individual patient characteristics (i.e. age, if they are regularly transfused)
- blood component
- equipment (contamination)
- concomitant medications and IV fluids
- procedures. i.e. clerical errors

17

What are the steps in a haemolytic reaction due to ABO mismatch?

Steps in haemolytic reaction:
1. patient antibodies coat donor RBC via surface antigens.
2. IgM antibodies activate the complement cascade
3. Formation of membrane attack complex
4. Agglutination of hemolysis of donor cells
5. Cytokine release (i.e. TFN) results in chills, rigors, dyspnea (shortness of breath), chest and/or flank pain and shock.
6. Haemoglobinuria, DIC, raised bilirubin and renal failure
7. Potentially death

NOTE: you can land up bleeding to death. Although a mismatch causes clotting, you eventually use up all of your clotting factors and then just bleed everywhere.

18

What is the treatment for an adverse event?

Treatment:
- fluid resuscitation to support circulation and maintain renal cortical perfusion
- airway support if require
- BP support if required

19

What are the most common causes of mismatched?

Most common causes of mismatches:
- patient’s blood has not been analyzed properly
- clerical errors
- incorrect labeling of blood samples/donations

20

How could mismatches be prevented?

- double checking clerical records
- Coombs test: mix some of donor and patient blood to see if there are any signs of reaction
- before transfusion, check that you have the right blood AND patient

21

What is Haemophilia?

Deficiency in clotting factor FVIII and IX. Now we have cryoprecipitate, and also F8 and 9 concentrates.

22

What viruses are tested for?

- HIV
- HTLV – Human T-Cell lymphotrophic viruses
- Hep B
- Hep C
- WNV – West Nile Virus
- Parvovirus B19

23

What are the 2 types of testing for viruses?

1. Serological – tests for exposure, antibody. Get samples from body fluid. BUT there is an eclipse phase. Then comes infectious phase, but to begin with although there are antibodies there aren’t enough to be detected. In total, the window period is how long it takes before you can detect it.

2. Nucleic Acid Testing (NAT) – tests for active infection, detects viral nucleic acids, get samples from site of infection. You can detect it earlier than serological. Drops window period significantly so decreases risk hugely.

24

what are the symptoms of bacterial sepsis?

- rigor
- fever
- severe chills
- hypotension
- tachycardia
- nausea and vomiting
- circulatory collapse
- DIC in severe cases (Disseminated Intravascular Coagulation) – can be fatal.

Main risk is with platelets because they are stored at room temp.

25

What are the sources of bacterial infection in a transfusion?

- skin
- bacteraemic donor
- contamination from environment
- contamination during preparation process
- contamination of ports

26

How can bacterial contamination be minimised?

Platelet screened 24 hours after collection (too low before that).
IMP (initial machine positive) is not conclusive as there may be false positives, so further testing (gram stains) can be done.

Other:
- first 30mls diverted away
- visual screening of blood
- screening of donors
- ensure aseptic technique
- ensure cleaning of labs, wards, water baths
- don’t use expired products
- apheresis platelets have less risk compared to pooled platelets (apheresis requires only one donor)