Transfusion Flashcards
What causes blood groups?
Arise from antigens
Red cell antigens are expressed on cell surface, can provoke antibodies
Describe 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
O is non functional allele
So A and B are (co-)dominant and O is recessive
What is the A blood antigen?
N-acetyl-galactosamine
What is the B blood antigen?
galactose
Describe the O blood gene
Non-functional allele
Describe antibodies present in the ABO blood groups
If blood group A; antibodies against B
If blood group B; antibodies against A
If O have antibodies against A and B
If AB have no antibodies against A and B
What are the types of transfusions?
Red cell
Fresh frozen plasma
Describe RhD
Rhesus
Negative individuals can make anti-D if exposed to RhD+ cells (transfusion or pregnancy)
What are blood donors screened regarding?
Sex, age, travel, tattoos
Tested for ABO and Rh blood groups
Screened for HepB/C/E, HIV, syphilus
What are indications for red cell transfusions?
- To correct severe acute anaemia, which might otherwise cause organ damage
- Improve QoL in patient with otherwise uncorrectable anaemia
- Prepare a patient for surgery or speed up recovery
- To reverse damage caused by patients own red cells; Sickle Cell Disease
Describe RBC transfusion
Stored at 4degreesC
Transfuse over 2-4hrs
1 unit increments ~5g/L
Describe platelet transfusion
Stored at ~22degreesC, shelf life 7 days
Transfuse over 20-30mins
What are indications for platelet transfusion?
Massive haemorrhage Bone marrow failure Prophylaxis for surgery Thrombocytopenia Cardiopulmonary bypass (only if bleeding)
Describe plasma components
FFP
- 1 unit from 1 unit blood
- stored frozen; 30mins to thaw
What are indications for FFP transfusion?
Massive haemorrhage
DIC w/bleeding
Prophylactic
Thrombotic Thrombocytopenic Purpura
Describe cryoprecipitate
1-2 pools if fibrin <1.0g/dl
Stored frozen -25 degrees; allow 20mins to thaw
Contains coagulation factors; FVIII, vWF, fibrinogen, FXIII
What is Coombs test?
Used to detect antibodies that work against RBCs
This can be due to incompatible transfusion or hemolytic disease
Direct; autoimmune hemolytic anaemia, passive anti-D
Indirect; cross-matching
What is required in massive haemorrhage?
Immediate supply of;
- 6 units red cells
- 4 units FFP
- 1 unit platelets
Describe prion disease
Transmittable by blood transfusion from early in disease in sheep
Describe haemolytic disease of newborn
RhD most immunogenic, also c, K
Other Rh antigens
positive DAT (direct antiglobulin test) at birth, anaemia, jaundice
How is haemolytic disease of newborn treated
Careful monitoring
- antibody titres
- doppler US
- intrauterine transfusions
Cellular therapies
- leucapheresis
- gene therapies
When would the different types of transfusion be indicated?
Red cell; anaemia
Platelets; thrombocytopaenia
Fresh frozen plasma; low coagulation factors
Cyroprecipitate; low fibrinogen
What can a patient with blood group O receive?
- Group A red cells
- Group A fresh frozen plasma
- Group A platelets
- Group A child
What can a patient with blood group A receive?
- O red cells
- O fresh frozen plasma
- O platelets
What are indications for use of cyroprecipitate?
Hypofibrinogenaemia; secondary to massive transfusion
DIC with bleeding and fibrinogen<1g/l
Bleeding associated w/ thrombolytic therapy
Renal or liver failure + abnormal bleeding
What samples are used in transfusion?
Group and Screen/save Cross match 'group specific' blood two sample policy 72hour (10day) validity
What are some acute transfusion reactions?
Pyrexia
Urticaria
Dyspnoea
Shock
