Blood transfusion Flashcards
Why transfuse?
○ Mainly because of bleeding
○ But also failure of production
Why are there different blood groups?
○ Arise from antigens
- =something that provokes an immune response
○ Red cell antigens are expressed on cell surface (proteins, sugars, lipids)
○ Can provoke antibodies
Explain ABO blood group antigens
- ABO gene encodes glycosyltransferase
- Glycans added to proteins or lipids on Red Cells
- A and B genes code for transferase enzymes
- A antigen is N-acetyl-galactosamine
- B antigen is galactose
- ‘O’ gene is non-functional allele
- So A and B are (co-)dominant and O is recessive
What are the antibodies each blood group have?
○ Blood group A, has antibodies against B
○ Blood group B, has antibodies against A
○ Blood group O, has antibodies against A and B
○ Blood group AB, has no antibodies against A and B
What happens with fresh frozen plazma?
The reverse is true for FFP as it is the antibodies
What is Anti-RhD?
- RhD negative individuals can make anti-D if exposed to RhD+ cells
□ Transfusion or pregnancy - Anti-D can cause transfusion reactions or haemolytic disease of the new-born
What is looked for in blood donors?
○ Extensive ‘behavioural’ screening ○ Sex, age, travel, tattoos………… ○ Tested for ABO and Rh blood groups ○ Screened for HepB/C/E, HIV, syphilis ○ Variably screened for: - HTLV1, malaria, West Nile virus, Zika virus…
What are the indications for red cell transfusion?
- To correct severe acute anaemia, which might otherwise cause organ damage (patients who are bleeding out)
- To improve quality of life in patient with otherwise uncorrectable anaemia
- To prepare a patient for surgery or speed up recovery (frowned upon now)
- To reverse damage caused by patient’s own red cells
□ Sickle Cell Disease
What should be considered when transfering red blood cells?
- Stored at 4°C
- Transfuse over 2-4 hours
- 1 unit increments ~5 g/L
What should be considered when transfereing platelets?
- 1 dose platelets (=4 pooled or 1 apheresis donor)
□ increments 20-40.109/L - Stored at ~22oC, shelf life 7 days
- Transfuse over 20-30 minutes
What are the indications for transfereing platelets?
□ Massive haemorrhage ® Keep platelet count above 75x109/l □ Bone marrow failure ® platelet count <10-15 × 109/litre ® or <20 × 109/litre if additional risk, e.g. sepsis □ Prophylaxis for surgery ® Minor procedures 50x109/l; ® More major surgery 80x109/l; CNS or eye surgery 100x109/l □ Cardiopulmonary bypass ® use only if bleeding
How should fresh frozen plazma be transfered?
- 1 unit from 1 unit of blood
- Stored frozen, allow 30 minutes to thaw
What are the indications to transfer fresh frozen plazma?
□ massive haemorrhage (use in 1:1 ratio?)
□ DIC with bleeding
□ ‘prophylactic’
What are the lab tests used when transfering Fresh frozen plasma?
- PT (prothrombin time)
- APTT (activated partial thromboplastin time)
How should cryoprecipitate be transfered?
- 1-2 pools if fib <1.0g/dl (1.5g/dl)
- Stored frozen; allow 20 minutes to thaw
What are the lab tests used in the transfer of cryoprecipitate?
Fibrinogen
What are the indications for transfereing cryoprecipitate?
- Renal failure
- Liver failure
What is Coomb’s test?
- Anti-human immunoglobulin □ If they clump together then it is a positive Coon's test - Direct □ autoimmune haemolytic anaemia □ passive anti-D □ haemolytic transfusion reactions - Indirect □ Cross matching
What is needed in the situation of a massive haemorrhage?
○ Good communication between all teams essential ○ Definitive management - Rapid Control of bleeding □ Obstetric intervention, surgery, interventional radiology ○ Immediate supply of: - 6 units red cells - 4 units FFP (cryoprecipitate?) - 1 unit platelets
What are the risks of blood transfusions?
- Never events: death or harm (transfusion of ABO incompatible component)
- Transfusion associated circulation overload (TACO): too much blood too quickly
- Transfusion associated lung infection (TRALI)
□ Transfused anti-leucocyte Abs in donor plasma interact with patient’s WBC
□ Bilateral pulmonary infiltrate
□ Supportive management, ventilation - Acute transfusion reaction (ATR)
- Febrile
- Allergic
- vCJD risk
What is prion disease?
- Transmittable by blood transfusion from early in disease in sheep
- 4 possible cases in humans
What steps are taken to reduce the risk of potential transmission of prion disease?
□ Leucodepletion 1998
□ UK plasma not used for fractionation
□ Imported FFP for all patients born after 1996
How do you manage a reaction to the transfusion?
- Stop transfusion
- Check patient identity against component label
- Consider: anaphylaxis, circulatory overload (TACO), acute haemolytic transfusion reaction (AHTR), bacterial infection, lung injury (TRALI) (other…)
What happens in haemolytic disease of foetus and newborns?
○ Mother has negative RhD blood cells but foetus has positive
○ The mother’s antibodies senses the negative RhD cells and then destroys them
○ IgG crosses the placenta and then destroys the foetus’ positive RhD blood cells
