Blood transfusions Flashcards
G n S and Cross match
GROUP and SCREEN – check ABO group and plasma antibodies in patient
Full crossmatch – checks patient’s blood against donor blood specifically
Grouping test
Use known anti-A, anti-B and anti-D reagents against the patient’s RBCs
o A positive result causes agglutination at the top
o A negative result will mean that the red cells stay suspended at the bottom of the vial
Antibody screen test
o Immune antibodies are IgG (these can cause a DELAYED transfusion reaction; extravascular haemolysis)
(1) use 2 or 3 reagent RBCs containing all important RBC antigens between them
(2) incubate patient’s plasma and screening cells using the Indirect Antiglobulin Technique (IAT)
• (a) Patient serum containing specific antibody added to reagent RBCs
• (b) Add Anti-Human Globulin (AHG) to promote agglutination
• (c) If +ve, reaction creates bridges between RBCs coated in IgG antibodies visible clumps
Compatibility of RBC, platelets and plasma
RBC- ABO+D
Platelets- D
Plasma- ABO
What is a unit of blood
10 g/L increase in Hb in a 70-80 kg patient
When do you need to do a GnS and crossmatch
For elective surgery, the patient should be group and screened before the operation
If antibodies are not present, a crossmatch is NOT needed but the sample should be saved in the fridge
If unexpected need for blood provided <10 mins (by electronic issue as no antibodies are present)
If antibodies are present, ALWAYS CROSSMATCH
RBC tranfusion indications
Major blood loss >30%
Peri-op Hb< 70
Post. hemp <80
Platelets tranfusion indications
Massive transfusion- aim for >75
Prevent bleeding (post chemo) if <10
Prevent bleeding surgery if <50
Platelets dysfunction- if active bleeding
1 Unit of platelets
Increase platelet count by 30-40 x 109/L
Most common acute reaction?
Transfusion associated circulatory overload (TACO)
• Often pre-existing cardiac/respiratory problems
Types of acute reactions (<24hrs)
o Acute haemolytic (ABO incompatible) o Allergic/anaphylaxis o Infection (bacterial) o Febrile non-haemolytic o Respiratory - TACO, TRALI
Delayed reaction (>24hrs) types
o Delayed haemolytic transfusion reaction (antibodies) – Duffy and Kidd o Infection (viral, malaria, vCJD) o TA-GvHD (week or 2 after transfusion) o Post transfusion purpura o Iron overload
Signs of acute reaction
Increase in temperature or pulse
Low BP
Fever, vomiting ect
What is Allergic transfusion reaction and treatment
Causes a mild urticarial or itchy rash sometimes with a wheeze – caused by allergy to donor plasma proteins
IV antihistamines
What is Febrile Non-haemolytic transfusion reaction
- Occurs during/soon after transfusion (blood or platelets)
- May cause a rise in temperature by around 1 degree, chills and rigors
- Caused by the release of cytokines from white cells during storage
• Tx: transfusion stopped or slowed and may need to be treated with paracetamol
What is ABO incompatibility
• Symptoms and signs of acute intravascular haemolysis (IgM-mediated):
o General: restless, chest/loin pain, fever, vomiting, flushing, collapse, haemoglobinuria (later)
o Monitoring: Low BP, High HR, High Temperature
Bacterial contamination
o General: restless, fever, vomiting, flushing, collapse
o Monitoring: Low BP, High HR, High Temperature
• Bacterial growth can cause endotoxin production which causes immediate collapse
o Platelets (stored at room temperature) > RBCs > FFP
Anaphylaxis after transfusion
• Severe, life-threatening reaction soon after the start of transfusion
o Shock = Drop in BP + Rise in HR
o Very breathless with wheeze
o Often laryngeal and/or facial oedema
- Mechanism: IgE antibodies in the patient cause mast cell degranulation
- Most allergic reactions are NOT severe, but some can be in the case of IgA deficiency- anti IgA AB against donors IgA
What is TACO and Sx and MX
• VERY COMMON; leads to pulmonary oedema/fluid overload – a TACO checklist exists to help alleviate
• Often caused by lack of attention to fluid balance – especially in…
o Cardiac failure, renal impairment, hypoalbuminaemia, very young/old
SoB
Low sats
High HR
High BP
• TACO responds to diuretics immediately (and has raised JVP)
What is TRALI
• Looks at bit like ARDS (more common in FFP or platelet transfusion)
o Anti-WBC antibodies in donor blood
o These interact with WBCs in the patient
o Aggregates WBCs stick to pulmonary capillaries release neutrophil proteolytic enzymes and toxic O2 metabolites lung damage
TRALI does NOT respond to diuretics (no JVP)
Delayed haemolytic transfusion reaction
Duffy and Kidd antigens
• Further transfusions with RBCs expressing same antigens antibodies will lyse RBCs (extravascular haemolysis)
o This is IgG-mediated so takes 5-10 days
High bilirubin, reticulocytes, low Hb
Antibody type against each RBC antigen
Anti-A, Anti-B = IgM antibodies
Delayed Reactions – Infections Anti-Rh, anti-Duffy, anti-Kidd = IgG antibodies
Delayed infection in tranfusions
CMV
Very immunosuppressed patients (e.g. stem cell transplant) can get fatal CMV disease
Leucodepletion/irradiation removes CMV in WBCs
o Parvovirus
Causes temporary red cell aplasia – so affects those with RBCs of a shortened life span
Affects foetuses and patients with haemolytic anaemias (e.g. sickle cell, hereditary spherocytosis)
o Variant CJD
Transfusion Associated Graft-Versus-Host Disease (TaGVHD)
• Rare but ALWAYS FATAL
o Donor’s blood will contain some lymphocytes that are able to divide
o Normally, the patient’s immune system will recognises these donor lymphocytes as foreign and destroy them
o In susceptible patients (very immunosuppressed), these lymphocytes are NOT destroyed
o Lymphocytes recognise patient’s tissue HLA antigens as foreign and attack
How to prevent GvHD
• Prevention: irradiate blood components for very immunocompromised patients or have HLA-matched components
Sx of GvHD
Diarrhoea
Liver failure
Skin desquamation
Bone marrow failure DEATH
What is Post-Transfusion Purpura and Tx
- Appears 7-10 days after transfusion of blood or platelets
- Usually resolves in 1-4 weeks but can cause life-threatening bleeding
- Affects Human Platelet Antigen (HPA) 1a -ve patients previously immunised via pregnancy or transfusion
• Treatment: IVIG
What is Post-Transfusion Purpura and Tx
- Appears 7-10 days after transfusion of blood or platelets
- Usually resolves in 1-4 weeks but can cause life-threatening bleeding
- Affects Human Platelet Antigen (HPA) 1a -ve patients previously immunised via pregnancy or transfusion
• Treatment: IVIG
When are pregnant women scanned for RBC antigens
• All women have a group and screen at around 12 weeks (booking) and again at 28 weeks
How can you treat a very anaemic baby in utero
• Sometimes, intrauterine transfusion may be needed if the baby is very anaemic
o The transfusion is done via the umbilical vein
o At delivery, monitor baby’s Hb and BR for several days as HDN can get worst
Mechanism of anti-D Immunoglobulin
The RhD +ve cells of the foetus will get coated by the exogenous anti-D immunoglobulin
They will then be removed by the mother’s reticuloendothelial system (spleen) before they can sensitise the mother to produce anti-D antibodies
For this to be effective, the anti-D injection must be given within 72 hours of the sensitising event
Examples of sensitising events for Haemolytic disease of the newborn
- Spontaneous miscarriages if surgical evacuation needed and therapeutic terminations
- Amniocentesis and chorionic villous sampling (CVS)
- Abdominal trauma (falls and car accidents)
- External cephalic version (turning foetus)
- Stillbirth or intrauterine death
Other antibodies that can cause HDN
o Anti-c and anti-Kell can cause severe HDN
o IgG anti-A and anti-B antibodies from group O mothers can cause mild HDN
This can usually be treated with phototherapy
