Blood Transfusions Flashcards
Why should alternatives to transfusion be considered prior to each transfusion?
a) to conserve the blood supply
b) to increase patient safety by avoiding clinically non-essential exposure to donor blood.
What is the first stage in processing blood after donation? What does this involve?
Leucodepletion –> whole blood is filtered before further processing to remove white cells
Why are WBCs removed during transfusion?
WBCs can carry infection or lead to transfusion reaction
After donation, what stage follows leucodepletion?
Blood is then separated into its components:
o RBCs
o Platelets
o Plasma
The plasma is then further separated.
What are the 3 forms in which plasma can then be given?
- Fresh frozen plasma (within 12 hours of donation)
- Cryoprecipitate
- Fractionation
What is cryoprecipitate?
This is manufactured from fresh, frozen plasma.
- Plasma is frozen and then defrosted at 4 degrees
- The bit of the plasma that melts at 4 degrees is collected –> this is the cryoprecipitate
What does cryoprecipitate contain?
Cryo is made from FFP which is frozen and repeatedly thawed in a laboratory to produce a source of concentrated clotting factors including Factor VIII, von Willebrand factor and fibrinogen.
What is blood plasma fractionation?
The general processes of separating the various components of blood plasma:
Clotting factors
Albumin; may be given to patients with cirrhosis
Immunoglobulins; may be given to immunocompromised
Factor concentrates (FVIII, FIX, prothrombin complex)
What is the most commonly transfused blood product?
RBCs
How long can RBCs be stored?
Stored at 4’C for up to 35 days from collection: most problems with blood will be due to incorrect storage
The plasma in RBC blood bags has been removed.
What is it replaced with? Why?
by a solution of electrolytes, glucose and adenine to keep the red cells healthy during storage
What is the usual transfusion time for RBCs?
1.30-3 hours
Haematocrit for RBC bags?
Haematocrit 60% (high volume of RBCs to total volume of blood)
A 1 unit transfusion of RBCs is expected to raised Hb by what?
10 g/L
What are the 4 major indications for a RBC transfusion?
- Significant bleeding (based on volume of blood loss)
- Acute anaemia
- Acute anaemia with mild symptoms
- Chronic anaemia
When is RBC transfusion in acute anaemia given until?
Symptoms resolve
When should you consider alternatives to transfusion in anaemia?
In treatable causes of anaemia:
- Iron
- B12
- Folate
- EPO treatment for patients with renal disease
What is the overall purpose of RBC transfusion?
restore oxygen carrying capacity
What is the adult therapeutic dose for platelets?
A pool of 4-6 donations, or a single apheresis donation
What are the 2 methods of collection of platelets?
- Pooled platelets
2. Apheresis platelets
Describe the ‘pooled platelets’ method of collection
- 1 unit is produced from 1 unit of whole blood
- 4-6 of these units are pooled together (usually from 4 whole blood donors) in a single pack
Describe the ‘apheresis’ method of platelet collection
- Blood cycles through apheresis machine, platelets are removed, and all other constituents are returned to the donor (selective removal)
- The amount of platelets collected with this procedure represents the equivalent of 4-6 units of random donor platelets
What are the 2 major uses of platelet transfusion?
- Treatment of severe bleeding due to severe thrombocytopenia (low platelets) or platelet dysfunction
- Prevention of bleeding in in patients with thrombocytopenia/dysfunction, or prophylaxis for surgery
What is thrombocytopenia?
Low platelets
What would the platelet count need to be maintained above in:
a) massive haemorrhage/bleeding
b) critical site bleeding (CNS)
a) maintain platelet count >50x10^9/L
b) maintain >100x10^9/L
What are the 3 major contraindications in platelet transfusion?
- Immune thrombocytopenic purpura
- Thrombotic thrombocytopenic purpura
- Heparin induced thrombocytopenia and thrombosis
Transfusion time for platelet?
20-30mins/unit
How are platelets stored?
Stored at 22’C on an agitator (risk of contamination by bacteria from donor’s are that can grow at storage temperature and be transmitted)
Shelf life of platelets?
5 days from collection
What is fresh frozen plasma (FFP) comprised of?
Contains all clotting factors at physiological levels (these are most important)
Average units of FFP given during transfusion?
Give 4-6 for average adult, therapeutic dose is 12-15mL/kg (4 units of FFP for average adult)
Transfusion time of FFP?
30 mins/unit
When is FFP thawed?
Immediately before use; 6 hours after thawing, the levels of the labile factors 5 and 8 begin to diminish
What are the 3 major uses of FFP?
- Replace clotting factors in patients with multiple factor deficiencies (acquired coagulopathies)
- To treat significant bleeding in patients with abnormal clotting results
- To correct abnormal clotting results before invasive procedures
What are 2 examples of multiple factor deficiencies (acquired coagulopathies)?
- Liver disease
2. Disseminated intravascular coagulation
In which 3 situations would you NOT transfuse FFP?
- To treat single factor deficiencies where a factor concentrate is available e.g. haemophilia A
- To correct abnormal clotting in patients who are not bleeding/having procedures
- To reverse warfarin
What clotting factors does warfarin inhibit (blood thinner)?
Warfarin inhibits clotting factors 2,7, 9 and 10 (people on warfarin are therefore deficient in these)
What is used to reverse warfarin instead of FFP?
Use Prothrombin complex concentrate instead –> This is a factor 9 (IX) complex, with a high concentration of vitamin K dependent factors 2, 9, 7, 10
What is cryoprecipitate mainly used for?
High fibrinogen conc
What does cryoprecipitate contain?
o Fibrinogen
o Von Willebrand factor
o Factors 8, 13
Main use of cryoprecipitate transfusion?
Mainly used as a concentrated source of fibrinogen in acquired coagulopathies:
o Massive haemorrhage
o Disseminated intravascular coagulation (DIC)
o Liver failure
These patients will all have a LOW fibrinogen.
Therefore used in:
- Treatment of bleeding in patients with low fibrinogen: maintain fibrinogen >1.5g/L
- Prevention of bleeding in patients with low fibrinogen: maintain fibrinogen >1g/L
Do NOT use to correct low fibrinogen in patients that are not bleeding/having procedures
How are Transfusion Transmitted Infections (TTI) mostly prevented?
- Donor questionnaire
2. Mandatory testing
How is the transmission by transfusion of variant Creutzfeldt-Jakob disease (vCJD) prevented?
Leucodepletion (also import plasma from countries with low incidence of vCJD)
How can blood components become contaminated after donation?
- bacteria from the donor’s skin during collection
- unrecognised bacteraemia in the donor
- contamination from the environment
(The risk increases with storage after donation)
What blood components are usually infected during donation? Why?
Platelets - stored at temperature of 22’C which favours the growth of bacteria
What is febrile non-haemolytic transfusion reactions (FNHTR)
Complication of blood transfusion; due to build-up of cytokines or other biologically active molecules that accumulate during storage of blood components.
o Common
o Onset: during or soon after the transfusion
o Often a problem with platelets: 10-30% after a platelet transfusion and 1-2% after an RBC transfusion
FNHTR is often caused by a problem with the…?
Platelets
Onset of FNHTR?
during or soon after the transfusion
Clinical features of FNHTR?
Rise of temperature >1’C from baseline
Rigors
Tachycardia
Treatment of FNHTR?
paracetamol, slow transfusion rate or mild or discard if temp rises >2^C or >39^C
What is transfusion associated circulatory overload (TACO)?
Complication of blood transfusion; oedema develops primarily due to volume excess or circulatory overload
Onset of TACO?
up to 24 hours after a transfusion
Symptoms and signs of TACO?
Similar to LV failure. Symptoms: Sudden dyspnoea Orthopnoea Tachycardia Hypertension Hypoxemia
Signs:
Raised BP
Elevated jugular venous pulse
Risk factors for TACO?
Elderly patients Small children Patients with compromised LV function Large transfusion volume Increased rate of transfusion
Prevention of TACO?
follow guidance on volume and rate of transfusion for each component
Treatment of TACO?
O2, diuretics, monitor fluid balance
What is the main cause of transfusion related deaths?
Pulmonary complications (e.g. TACO)
Are TACo and FNHTR immunological or non-immunological complications of transfuion?
Non-immunological
What is an acute haemolytic transfusion reaction?
Involve haemolysis of transfused red cells due to the presence of preformed antibodies against antigens that are expressed on the transfused RBC
Most common cause of an acute haemolytic transfusion reaction?
ABO-incompatible transfusions
Describe the haemolytic reaction if a patient with blood group A is transfused with blood group B blood
Patient is blood group A; has antigen-A on RBCs and have anti-B antibodies in blood
If patient transfused with blood group B; anti-B antibodies in patient blood will start to break new RBCs down and release free Hb in the circulation and activate complement system
What does acute haemolytic transfusion reaction release into the blood?
Free Hb
What are the 3 major deleterious effects of free Hb?
- Kidney damage
- Complement activation
- Nitric oxide depletion
How can free Hb cause kidney damage?
tubular deposition of Hb causes oxidative damage to renal cells –> acute kidney injury
How can complement activation due to free Hb cause:
a) fever, rigors, hypotension
b) bleeding?
a) endothelial cells –> cytokine shower
b) endothelial cells –> express pro-coagulant molecules –> clotting cascade is activated –> disseminated intravascular coagulation –> bleeding
How can free Hb lead to NO depletion?
Free Hb binds to and inactivates nitric oxide leading to vasoconstriction, hypertension and angina
Signs and symptoms of acute haemolytic transfusion reaction?
Fever and chills Back pain Hypotension/shock Haemoglobinuria (may be first sign in anaesthetised patients) Increased bleeding (DIC) Chest pain Sense of impending death
Onset of acute haemolytic transfusion reaction?
severe reactions may occur early in the transfusion (15 mins), but milder reactions may occur later, but usually before the end of transfusion
Mortality rate of acute haemolytic transfusion reaction?
Fatal in 20-30% –> make sure you repeat cross-matching!
What test is done to prevent adverse transfusion reactions?
Pre-transfusion testing
What 3 aspects does pre-transfusion testing involve?
- Determine ABO group
- Determine Rh(D) group
- Test patient’s plasma for antibodies against other clinically significant blood group antigens (i.e. look for any other antibodies that you wouldn’t expect to find – blood group A patients should only have anti-B antibodies)
During the plasma screen in pre-transfusion testing, what are the next stages if clinically significant non-ABO antibodies are detected?
antibody identification by testing the plasma against a panel of red cells containing all clinically significant blood groups –> find out what that antibody is reacting to
What are potential causes of clinically significant non-ABO antibodies?
previous transfusion, pregnancy
What is the final test done before transfusion of RBCs (after pre-transfusion testing)?
Compatibility testing
What does compatibility testing involve?
The crossmatching of selected donor blood of appropriate ABO and RhD type for a patient requiring a blood transfusion.
Patient’s plasma is mixed with aliquots of the donor red cells to see if a reaction (agglutination or haemolysis) occurs
If there is no reaction during compatibility testing, what does this mean?
RBC units compatible –> no risk of acute haemolysis
If there is a reaction during compatibility testing, what does this mean?
RBC units incompatible –> risk of acute haemolysis
What is a delayed haemolytic reaction?
o Due to post-transfusion formation of new immune IgG antibodies against RBC antigens other than ABO.
o Occurs more than 24 hours after the transfusion
o Onset: 3-14 days following a transfusion of RBC
Clinical features of a delayed haemolytic reaction?
Fatigue
Jaundice
Fever
Laboratory findings in delayed haemolytic reaction?
Drop in Hb – extravascular haemolysis
Increased LDH
Increased indirect bilirubin
How can the diagnosis of delayed haemolytic reaction be confirmed?
direct and indirect anti-globulin test should be positive
What is a direct anti-globulin test?
Testing to see if the RBCs are bound to antibodies (they shouldn’t be):
o incubate red cells with anti-human globulin reagent (antibodies which can recognise human antibodies).
o If the red cells of the patients have antibodies bound to the surface, the reagent will bind to these and cause agglutination.
o This will give rise to a positive test
i.e. is the patient’s blood attacking the new blood?
Patient’s can have allergic reactions to transfused blood.
What are these due to?
Due to hypersensitivity of the recipient to transfused ‘random’ proteins
Clinical features of allergic reactions to transfused blood?
o Rash o Urticaria o Pruritis o Rigors and fever o Periorbital oedema
What are allergic reactions to transfused blood most often due to?
Common transfusion reaction (1%), more often after transfusion of components that contain PLASMA:
o FFP
o Cryoprecipitate
o Platelets
Treatment of allergic reactions to transfused blood?
antihistamines, steroids, slow rate/discontinue transfusion
Allergic reactions to transfused blood can lead to anaphylactic reactions.
These are severe and life-threatening.
What are the signs and symptoms?
Laryngeal oedema
Bronchospasm
Hypotension
Swelling
Risk factors for anaphylactic reactions to transfused blood?
patients with IgA deficiency who have anti-IgA antibodies –> can become allergic to IgA in blood product they are receiving
Treatment for anaphylactic reactions to transfused blood?
ABCDE, IM adrenaline, antihistamine IV, steroid IV, fluid
What is transfusion related acute lung injury (TRALI)?
Complication of blood transfusion
- Antibody in blood product which attacks WBCs of patient
- WBCs become activated
- Activated WBCs lodge in pulmonary capillaries
- Release substances that cause endothelial damage and capillary leak
Transfusion of what is most common with TRALI?
transfusion of plasma rich components (platelets, FFP)
Diagnosis of TRALI?
o Clinical and radiological diagnosis o Sudden onset of acute lung injury occurring within 6 hours of transfusion o Hypoxemia o New bilateral chest X-ray infiltrates o No evidence of volume overload
How to differentiate between TACO and TRALI?
o With both, patients present with respiratory distress due to acute onset pulmonary oedema.
o With TRALI, patients also often have hypotension and fever, and can have transient leukopenia.
o With TACO, one would typically expect hypertension and a lack of fever and leukopenia.
Why is plasma used in UK only from male donors?
Plasma from female donors is not currently used because it is more likely to contain antibodies that could cause a serious reaction when given to a patient; females are sensitised to antigens during pregnancy
