Transfusion Flashcards
Describe the ABO blood groups and their significance in transfusion?
ABO groups refer to the antigens found on someones RBC’s.
Group A: have surface A antigens and contain anti B antibodies in there serum
Group B: have surface B antigens and contain anti A antibodies in there serum
Group O: have no surface antigens (universal donor) but contain both anti A and B antibodies in their serum
Group AB: have both A and B surface antigens but contain no antibodies in there serum (universal recipient)
Mismatched blood transfusions cause immediate transfusion reaction and often renal failure or death!
Describe the principles of group and save and cross match blood tests?
Group and Save involves taking a sample from the patient and determining what ABO group the patient’s blood is, and screening for antibodies that may cause a haemolysis reaction in transfused blood, the patients blood is then stored.
In addition to this, cross matching involves mixing part of the patient’s sample with donor blood units, to ensure no abnormal reaction occurs (Coomb’s test). However this takes longer.
What are the Rhesus antigens and why are they important?
As well as ABO patients also have a complicated rhesus blood group.
There are 5 key rhesus antigens: c, C, D, e, E.
Rhesus mismatched products can cause transfusion reactions but less commonly than an ABO mismatch.
85% of the population are Rhesus positive (this is referring to Rhesus D). A mismatch with rhesus D is the most likely rhesus antigen to cause a transfusion reaction.
Describe the pathophysiology of rhesus haemolytic disease of the newborn?
Rhesus D negative mother gives birth to a rhesus D positive baby.
During child birth blood mixes and the mother develops anti D antibodies.
If in her next pregnancy the child is rhesus D +ve then the mothers anti D antibodies will attack the baby in utero.
This can cause fetal anaemia, fetal hydrops and fetal death.
How is rhesus disease prevented?
Stop rhesus D -ve mothers from developing antibodies.
This is done by giving the mothers exogenous anti D immunoglobulin injection to immobilise any rhesus D +ve cells therefore no antibodies will be created.
What are the different blood products which can be transfused?
Packed red cells (concentrated red cells) 1 unit roughly corresponds to 10g/dl in Hb in average 70kg adult
Platelets
Fresh frozen plasma (used to replace clotting factors)
Cryoprecipitate (rich in Fibrinogen, vWF, factor VIII)
Cryopoor
Huma albumin solution
Describe when you should consider transfusing a patient with pack red cells?
It is a clinical decision and shouldn’t be done based on Hb alone.
Consider whether patient can be treated with iron + folate.
If actively bleeding heavily clearly transfuse.
When should platelets be transfused?
For the treatment or prevention of bleeding due to thrombocytopenia or platelet dysfunction.
Examples:
-Recent history of thrombocytopenia-related life-threatening bleed: Platelet count < 50-100k
Planned invasive procedure:
LP, -centesis: < 30-50k
Major surgery: < 50-100k
What are important things to consider when giving platelets?
Must be ABO compatible as it contains donor antisera in the plasma.
Stored at a slightly higher temperature, therefore there is an increased risk of bacterial contamination.
If the patient is reacting badly think sepsis.
What is the difference between fresh frozen plasma and cryoprecipitate?
FFP contains all of the soluble factors of coagulation. It should be used in patients with multiple factor deficiencies that are bleeding.
Cryoprecipitate: is rich in Fibrinogen, vWF and factor VIII. It should be used hypofibrinogenemia, vonWillebrand disease, and in situations calling for a “fibrin glue.”
Note both must be ABO compatible, for platelets, FFP and cryoprecipitate AB is the universal donor as the antisera will not contain any anti A or B.
What is human albumin solution used for?
It is used in plasma exchange and as a plasma expander.
It works as a plasma expander by causing extracellular fluid to go into the circulation.
Should be used by specialists only as you can easily overload a patient if too much is given and it is very expensive.
How should you deal with massive blood loss as a general approach.
ABCDE
C:
- 2 wide bore cannulas IV access (or IO)
- initiate major haemorrhage protocol
- give crystalloids until o neg available and send for a rapid x match
- keep on giving blood as a bolus until patient is haemodynamically stable
What are some specific points to consider when giving blood in major blood loss?
- Rapid transfusion should be done through a blood warmer as hypothermia causes defective coag cascade
- Check HCO3, pH and Ca as plasma buffers are lost in bleeding therefore can become acidotic
- Ca is bound in red cell bags so can become low
- Check platelets/fibrinogen/clotting every 4 units
- Give FFP, cryo and platelets as dictated by blood results
What occurs in a haemolytic transfusion reaction?
Symptoms:
- Agitation
- Flushed
- Abdo/flank pain
Signs:
- Fever
- Hypotension
- DIC
- Hb uria
Essentially you become shocked due to a massive activation of complement.
Main differential is sepsis due to transfusion of contaminated blood.
How are transfusion reactions managed?
- Stop transfusion
- Recheck bag and identity of patient
- Check:
- FBC looking for haemolysis/infection
- Coag ?DIC
- U/E’s looking for acute tubular necrosis/acute renal failure
- Urinalysis looking for haemoglobinuria - Return blood bag to blood bank
- Catheterise and monitor UO
- IV fluids
