Haem - Blood transfusion Flashcards
What are ABO blood groups determined by
(1) antigens on RBC membrane
(2) naturally occurring IgM in the plasma
- IgM against normal RBC antigens
- IgG against atypical RBC antigens
What are the types of blood group antigens
ABO
Rhesus
Kell (K)
M
N
S
Duffy (Fy) - delayed transfusion reaction
Kidd (Jk) - delayed transfusion reaction
What happens when you give RhD +ve blood to a RhD -ve patient and what proportion of the population are RhD +ve
Formation of anti-D antibodies (IgG) → no acute reaction → DELAYED haemolytic reaction
15% RhD -ve
Which blood group RBCs and plasma can you give to patients with blood group:
A
B
AB
O
RBCs:
A: A, O
B: B, O
AB: A, B, AB, O
O: O
Plasma:
A: A, AB
B: B, AB
AB: AB
O: A, B, AB, O
What should be done before blood transfusion
Group and Screen - check ABO group and plasma antibodies in patient
Full crossmatch - patient’s blood against donor’s blood
How does group and screen work
- Mix known antibodies (A,B,D) against the patient’s RBCs
- Add reverse group RBCs with the patient’s plasma (IgM)
Positive = agglutination at the top
Negative = red cells suspended at the bottom of the vial
How does crossmatching work (antibody screens)
Patient’s plasma is incubated with donor red cells at 37 degrees for 30-40 mins
Detects antibody-antigen reaction that destroys the RBCs leading to extravascular haemolysis
- Use 2 or 3 reagent RBCs containing the important RBC antigens between thme
- Incubate patient’s plasma and screening cells using Indirect antiglobulin technique (IAT)
- Patient serum added to reagent RBCs
- Add Anti-human globulin (AHG) to promote agglutination
- If postitive, reaction creates bridges between RBCs coated with IgG → visible clumps
How are RBCs stored and what is the infusion time
Stored at 4 degrees for 35 days
Transfuse in 4 hours of leaving the fridge
2-3 hours transfusion time for 1 unit
How are platelets stored and what is the infusion time
22 degrees for 7 days
Transfusion time 20-30 minutes per unit
How is plasma stored and what is the infusion time and why must it be given quickly
Plasma is frozen
Needs 30-40 minutes to thaw
- FFP: once thawed can keep at 4 degrees for 24 hours
- Cryoprecipitate: once thawed keep at room temp, use within 4 hours
20-30 minutes infusion time per unit
Stored at room temp → bacteria can contaminate quickly
A reaction with plasma is more likely to be allergic as plasma is frozen and so is unlikely to be contaminated by microbes
What are the indications for blood transfusion
Major blood loss: >30% volume lost
Peri-op, critical care: Hb <70g/L
Post chemo: Hb <80g/L
Transfusion dependent: <70g/L (asymptomatic), <80g/L (symptomatic)
Symptomatic anaemia: IHD, SOB, ECG changes
(If iron/folate/B12 deficiency → treat this first unless they are actively bleeding)
What are the cross matching requirements for plasma
ABO compatible, rhesus group does not matter
Do not need to cross match
What are the options for autologous blood transfusion
Intra-operative cell salvage: blood collected in surgery, centrifuged, filtered, and washed before reinfusion
Post-operative cell salvage: a wound drain collects blood loss post-op, this is filtered and re-infused (seen in orthopaedic operations e.g. knee surgery)
What are the special requirements for intra-uterine transfusions, neonatal transfusions, pregnant women, immunosuppressed patients, and those who have experienced severe allergic reaction
Intra-uterine, neonatal, pregnant women: CMV negative
Immunosuppressed: irradiated blood (pt cannot destroy incoming donor lymphocytes which would cause TA-GvHD)
Severe allergic reaction: washed
What are the indications for platelet transfusion
Massive loss: Platelets <75x10^9
Preventing bleeding Post-chemo: <10x10^0
Preventing bleeding in Surgery: <50x10^9, <100 if a critical site e.g. eye, CNS
Platelet dysfunction or immune causes IF actively bleeding
Active bleeding + TTP, DIC, HIT
What are the containdications to platelet transfusion
Heparin-induced thrombocytopaenia and thrombosis
Thrombotic thrombocytopenic purpura (TTP)
What are the indications for fresh frozen plasma
Massive blood loss >150mil/min
DIC AND active bleeding
Liver disease + risk : PT ratio >1.5x normal
Coagulation factor replacement when factor concentrate is not available (contains all clotting factors)
What does cryoprecipitate contain
More fibrinogen + FVIII and vWF, fibronectin, fVIII, platelet microparticles, IgA, albumin
What defines acute reactions to transfusion and what are the types
<24hrs
Transfusion associated circulatory overload (TACO) - most common
Acute haemolytic (ABO incompatible)
Allergic/anaphylaxis
Infection (bacterial)
Febrile non-haemolytic
Acute lung injury (TRALI)
What defines delayed reactions to transfusion and what are the types
> 24 hours
Delayed haemolytic transfusion reaction (antibodies) – Duffy and Kidd
Infection (viral, malaria, vCJD)
TA-GvHD (week or 2 after transfusion)
Post transfusion purpura
Iron overload
What is SHOT (transfusion)
Serious hazards of transfusion
National reporting scheme for serious transfusion outcomes
What are the early signs of an acute reaction and how may you pick these signs up in a patient who is unconscious
- Raised temperature and pulse, reduce BP
- General symptoms: fever, rigors, flushing, N&V, dyspnoea, chest pain, urticaria, itching, headache, collapse
Continuous monitoring
Before transfusion: baseline temp, RR, BP, pulse
Repeat post-transfusion: 15 mins and every hour
Describe Febrile Non-Haemolytic Transfusion Reaction (FNHTR) and its treatment
Occurs during/soon after transfusion (blood or platelets)
(Now rare due to leucodepletion of blood)
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
Describe allergic transfusion reactions and its treatment
Common, especially with plasma (proteins in plasma)
Causes a mild urticarial or itchy rash sometimes with a wheeze – caused by allergy to donor plasma proteins
Can occur during or after (even after patient has left) transfusion transfusion usually stopped or slowed
Recipients have a history of atopy
Tx: IV antihistamines
Describe ABO incompatibility reactions and what investigations should be done if suspected
Symptoms and signs of acute intravascular haemolysis (IgM-mediated): restless, chest/loin pain, fever, vomiting, flushing, collapse, haemoglobinuria (later)
Causes: failure of bedside check, wrongly labelled sample, lab error
Ix: FBC, Biochem, Coagulation, repeat X-match, DAT
Describe bacterial contamination reactions in transfusion
Presents similarly to ABO mismatch
Bacterial growth can cause endotoxin production which causes immediate collapse
May be: from the donor (GI, dental, skin infection) OR introduced during processing (environmental or skin)
Platelets (stored at room temperature) > RBCs > FFP
How is bacterial contamination in transfusion prevented
Donor questioning + arm cleaning + diversion of first 20 mL into a pouch (used for testing)
Platelets: stored for 7 days and screened for bacteria before release
Red Blood Cells: stored in a controlled fridge (4), if kept out >30 mins → put back in fridge for 6 hours
Describe anaphylaxis during transfusion
Severe, life-threatening reaction soon after the start of transfusion → hypotension + tachy ± laryngeal/facial oedema, wheeze, SOB
Mechanism: IgE antibodiesin the patient cause mast cell degranulation
Increased severity of allergic reaction due to IgA deficiency
Describe Transfusion Associated Circulatory Overload (TACO), its signs and symptoms and what investigations should be done
Most common acute transfusion reaction
Pulmonary oedema/fluid overload
Caused by lack of monitoring of fluid balance, especially in HF, renal impairment, hypoalbuminaemia
S/S: SOB, low sats (fluid overload), tachy and HTN (HF)
CXR: fluid overload
Describe Transfusion Related Acute Lung Injury (TRALI)
Similar presentation to ARDS, NO fluid overload (unlike TACO)
More common in FFP or platelet transfusion
Anti-WBC Abs in the donor blood → react with pt WBCs → aggregates stick to pulmonary capillaries → neutrophil proteolytic enzymes + toxic O2 metabolites
Features: FEVER, SOB, low sats, high HR, high BP
CXR: bilateral pulmonary infiltrates during/within 6 hours of transfusion due to circulatory overload and other causes
What is the difference in treatment response between TACO and TRALI
TACO responds to diuretics immediately (and has raised JVP)
TRALI does NOT respond to diuretics (no JVP)
How is TACO and TRALI prevented
Use male donors for plasma and platelets (no pregnancy or previous transfusions, so no HLA/HNA ABs)
Describe Delayed Haemolytic Transfusion Reaction and what investigations should be done
Usually to Duffy and Kidd antigens
Patients develop ABs against the RBC antigen they lack (alloimmunisation) → any further transfusions with those RBCs → extravascular haemolysis
IgG mediated, takes 5-10 days
Ix: bilirubin, FBC, LDH, reticulocytes, urine dip, DAT, U&Es
Describe infection during transfusion as a delayed reaction
Anti-A, Anti-B = IgM antibodies | Anti-Rh, anti-Duffy, anti-Kidd = IgG antibodies
Examples = malaria, viral infections (CMV, parvovirus), variant CJD (“Mad Cow Disease)
Symptoms may occur months or years after the transfusion
Describe Transfusion Associated Graft-Versus-Host Disease (TaGVHD)
Rare but ALWAYS FATAL
Can take weeks to months to come on after transfusion
Susceptible patient (immunosuppressed) do not destroy the donor lymphocytes → donor recognises patient HLA as foreign → attacks all HLA antigens (gut, liver, skin, bone marrow)
S/S: diarrhoea, liver failure, skin desquamation, bone marrow failure, death
How is Transfusion Associated Graft-Versus-Host Disease (TaGVHD) prevented
irradiate blood components for very immunocompromised patients or have HLA-matched components
Describe post-transfusion purpura and its treatment
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 (HPA-1a AB)
Treatment: IVIG
Describe iron overload
Lots of transfusions (past thalassaemia patients), iron will accumulate in their body
There is about 200-250 mg of iron per unit of blood
This can damage the liver, heart and endocrine organs
Requires chelation
What are the complications of haemolytic disease of the newborn
Foetal anaemia (haemolytic)
Haemolytic disease of the newborn (anaemia, high BR → builds up after birth as not removed by placenta)
Hydrops fetalis
What is the pathophysiology of haemolytic disease of the newborn
- RhD postive foetus → IgG Abs cross the placenta
- Anti-D antibody development (sensitisation)
- In subsequent pregnancies → RhD positive foetus → Abs cross the placenta and destroy foetal cells
What is the prevention for haemolytic disease of the newborn
Group and screen and rhesus testing at booking (8-12) and at 28 weeks
If Rh- → anti-D Ig (foetal antigens removed by the spleen before sensitisation can occur)
If antibodies are present: check if father has antigen, monitor level of antibody + check ffDNA sample to allow for identification of baby’s RhD group
Monitor foetus for anaemia via MCA doppler US
May require early delivery OR intrauterine transfusion
- Via umbilical vein
- Monitor baby’s Hb and BR for several days
- May require exchamge transfusion
When should anti-D be given
28 weeks (1500IU) if mother is RhD - OR 28 and 34 weeks
At delivery if the baby is RhD positive (1500IU)
Within 72 hours of a sensitising event
Foeto-maternal haemorrhage is likely to occur (and you do NOT know the Rh status of the baby)
+ Kleihauer test >20w to determine what dose is needed
- 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
What is the relevance of Anti-Kell antibodies, anti-A and anti-B antibodies in pregnancy
Kell causes reticulocytopenia in a foetus as well as haemolysis
Anti-A/anti-B: can cause mild HDN → treate with phototherapy
