Blood Transplantation Flashcards
Where do the different blood groups arise from?
- Arise from antigens
- These antigens are on the cell surface and can provoke antibodies
Which antigens are present on the surface of the red blood cells?
- Type A: has A antigens
- Type B: has B antigens
- Type AB: has A and B antigens
- Type O: has no antigens on the surface of the RBC
Which antibodies do each blood type have?
- Group A: antibodies against B
- Group B: antibodies agaisnt A
- Group O: antibodies against A and B
- Group AB: no antibodies against A and B
List the blood groups from most to least common
- O (46%)
- A (42%)
- B (9%)
- AB (3%)
Why is the Rhesus gene important with regard to blood groups?
If it is deleted then the patient is Rhesus negative. If they are then exposed to RhD positive blood it can cause haemolysis - very important for foetuses
What are blood donors screened for?
- Behavioural screening (sex, age, travel, tattoos etc.)
- Blood group and Rh blood group
- HepB/C/E, HIV and syphilis
- Variably screened for HTLV1, malaria, West Nile virus, Zika virus
What are the indications for red cell transfusion?
- To correct severe anaemia
- To improve quality of life in a patient who has otherwise uncorrectable anaemia
- To prepare a patient for surgery or speed up recovery
- To reverse damage caused by a patient’s own red cells e.g. Sickle cell disease
How are red blood cells transfused?
- Stored at 4 degrees
- Transfused over 2-4hrs
- 1 unit increments (approx. 5g/L)
How are platelets transfused?
- 1 dose of platelets
- Stored at 22 degrees
- Transfuse over 20-30 minutes
- Try not to cross blood groups but can
What are the indications for platelet transfusion?
- Massive haemorrhage
- Bone marrow failure
- Prophylaxis for surgery (CNS or eye surgery need higher platelet counts than the rest)
- Cardiopulmonary bypass (if bleeding)
- DIC if the patient is bleeding
What are the indications for fresh frozen plasma?
- Massive haemorrhage (use in 1:1 with RBCs)
- DIC in the presence of bleeding
- Thrombotic thrombocytopenic purpura
- Replacement of coagulation factor deficiencies where factor concentrate is unavailable
What is the indication for cryoprecipitate?
- Fibrinogen <1.0g/dl
- Hypofibrogenaemia secondary to massive transfusion
- DIC with bleeding and fibrinogen
- Bleeding with associated with thrombolytic therapy
- Renal/liver failure with abnormal bleeding
- Inherited hypofibrinogenaemia if fibrinogen concentrate is unavailable
- Fibrinogen conc. on its way
What happens when blood is grouped and screened/saved?
- ABO and RhD type
- Checked against historical records
- Screen for allo-antibodies in the serum
How does Coombs test work?
It tests for antibodies in the serum. If the Ab is present then the RBCs will clump together
What can a direct and indirect Coombs test show?
- Direct: autoimmune haemolytic anaemia, passive anti-D and haemolytic transfusion reactions
- Indirect: cross matching
What happens when a mother is RhD negative and the baby is RhD positive?
If nothing is done then the baby’s red blood cells can haemolysise, the baby can become anaemic, go into cardiac failure and die
Which antigens can cause haemolytic disease of the newborn and how does it present?
- RhD, c and k most immunogenic
- Other Rh antigens, Jka and ABO less immunogenic
- Positive DAT at birth, anaemia and jaundice
How can haemolytic disease of the newborn be treated
- Exchange transfusion when the baby is born
- Anti-D prophylaxis
- Careful monitoring: antibody titres, doppler USS and intrauterine transfusion
- Neonatal alloimmune thrombocytopenia (NAIT) - similar process for platelets
What cellular therapies are available?
- Leucapheresis: bone marrow harvests and donor lymphocyte infusions
- Other banks: bone, milk, tendons, heart valves, faecal, islet cells and mesenchymal stem cells
- Gene therapies
What is the threshold for red cell transfusion?
-A haemoglobin of 70 (90-100 in patients with cardiac impairment)
What are the alternatives to transfusion for surgery?
- Pre admission clinic: reversal of anaemia
- Intra-operative cell salvage
Why are those born after 1996 given treated FFP?
Because there is a risk of new variant CJD
Which patients need irraditated blood?
Immunosuppressed patients (to prevent graft versus host disease)
What are the risks of a blood transfusion?
- Transfusion of ABO incompatible components
- TACO (transfusion associated circulatory overload)
- TRALI (transfusion associated lung injury)
- ATR (acute transfusion reactions)
- Febrile
- Allergic
- Hypotensive
What are the potential acute transfusion reactions and how are they treated?
- Pyrexia: anti-pyretic
- Urticaria: antihistamine
- Dyspnoea: O2, diuretic, ventilation and adrenaline
- Shock: adrenaline, hydrocortisone, antihistamine, IV fluids, ICU, ventilation, antibiotics and FFP/platelets if DIC
