Blood Transfusion 1 Flashcards
What are the important blood groups?
ABO and RhD
What are the blood components?
red cells, fresh frozen plasma, platelets, cryoprecipitate
What is the process of blood donation?
selection of donors, testing of donations, processing blood into components
What are the 4 rights of blood?
Giving the right blood to the right patient at the right time for the right reason
What antibodies are present in Group A blood?
Anti B
What antibodies are present in Group B blood?
Anti A
What antibodies are present in Group AB blood?
None (universal receiver)
What antibodies are present on Group O blood?
Anti A and Anti B (Universal Donor)
What does ABO/ RhD incompatibility cause?
Intravascular Haemolysis
What is RhD?
Red cells which carry the RhD antigen are ‘RhD positive’
These patients can receive RhD negative (just a waste!) or RhD positive red cells
What can’t you give RhD negative patients?
RhD negative patients lack the RhD antigen
These patients can make immune anti-D if exposed to RhD positive red cells
Immune anti-D antibodies are IgG, which do not cause direct agglutination of RBCs so not immediate haemolysis & death, but delayed haemolytic transfusion reaction
How much of the population is RhD positive/ negative?
85% of the population are RhD-positive and 15% RhD-negative
What happens if there is no RhD negative blood to transfuse?
RhD-negative blood is often in short supply so it may be necessary to use RhD-positive blood for the transfusion of RhD-negative patients.
Why do pregnant women care about Rhesus Status?
Immune Anti-D made by a Rh negative mother exposed to Rh positive blood, can cause haemolytic disease of the newborn or severe fetal anaemia and heart-failure (hydrops fetalis) in RhD-negative females of child bearing potential.
How do you test patients ABO and RhD group?
use known anti-A and anti-B and anti-D reagents against patient’s RBCs
And “reverse group”: known A and B group RBCs against patient’s plasma (IgM antibodies)
Positive = agglutination (clumping)
Negative =
Red cells stay suspended
The BLOOD GROUP is done before every transfusion, even if it has been done many times before
What are the results of column agglutination?
Positive = agglutination (cells stay at the top)
Negative = No agglutination, cells pass through the beads (or gel) to the bottom
Agglutination with anti-B and A1 cells
No reaction with anti-A and anti-D or with B cells
These techniques can be ‘automated’ or ‘manual’: room temp, 10 mins
What do we do about the other RBC antigens?
Can’t test all other RBC antigens (100s)
But about 1-3% of patients have immune RBC antibodies to one or more RBC antigen
Must identify clinically significant RBC antibodies and transfuse RBCs that are negative for that antigen to prevent a DELAYED HAEMOLYTIC TRANSFUSION REACTION
How do you do an antibody screen on a patients blood plasma?
Use 2 or 3 reagent red cells containing all the important red cell antigens between them
Screen by incubating the patient’s plasma and screening cells using IAT** technique
**INDIRECT ANTIGLOBULIN TECHNIQUE (bridges red cells coated by IgG, which can’t themselves bridge 2 red cells – to form a visible clump. Takes 30 mins’ incubation at 37°C)
Group and Save
The ANTIBODY SCREEN is done before every transfusion, even if it has been done before, because can make new antibodies.
How has the screening process been automated?
Bar coded samples (id correct throughout – no mix up)
Computer interfaces
Robotic sample and reagent handling
Liquid level sensors (? failed to add reagent)
Reading of results by image analysis
Interpretation of results
Download to patient record
How do you issue blood?
DONOR RBCs ARE LABELLED WITH
ABO & D TYPE
THEY ARE ALSO LABELLED WITH
OTHER Rh ANTIGENS AND K
Select the correct ABO and D type from stock fridge
Select antigen negative blood if RBC antibody detected in antibody screen and ID panel
Select K negative blood for females of childbearing potential
What is a full serological crossmatch?
Indirect antiglobulin technique:
Patient plasma incubated with donor red cells at 370C for 30-40 mins, will pick up antibody antigen reaction that could cause destroy the red cells and cause extravascular haemolysis. Add antiglobulin.
IgG antibodies can bind to RBC antigens but do not crosslink so AHG reagent is added
What is immediate spin?
IMMEDIATE SPIN (SALINE, ROOM TEMPERATURE) Incubate patient plasma and donor red cells for 5 minutes only and spin, will detect ABO incompatibility only
IgM anti-A and/or anti-B bind to RBCs, fix complement and lyse the cell
What is electronic crossmatch?
Electronic issue (EI) is the selection and issue of red cell units where compatibility is determined by IT system, without physical testing of donor cells against patient plasma.
What are the pros of electronic crossmatch?
Quicker Fewer Staff No need to have blood standing by just in case Remote issue Better stock management
Who is involved in the blood decision?
Patient blood management is the modern approach to clinical transfusion practice.
You should remember this whenever you consider whether transfusion is needed.
It is the same as any other treatment decision. And must involve the patient.
What should we consider before giving blood?
Is the patient bleeding? What are the blood results? Is the patient symptomatic? Will a transfusion solve the problem? What are the risks of transfusion? Are there alternative treatments?
How do you consent patient for blood?
Valid’ consent is required for transfusion (verbal & written),
Alternatives should be offered if appropriate
If transfused in an emergency, patient must be informed afterwards
Involve patients in the process to ensure they get the right blood and the right ‘special requirements’
When are red cells given?
Give ABO/D compatible
Group O negative in emergency
Consider special requirements
How are red cells given?
Stored at 4°C for 35 days.
Must be transfused within 4 hours of leaving fridge
Transfuse 1 unit RBC over 2-3 hours
When are platelets given?
ABO/D antigens weakly expressed
Should be D compatible; no need to cross match
Consider special requirements
How are platelets given?
If group O given to A, B or AB patients select ‘high-titre’negative (anti-A/B antibodies)
Stored at 22°C for 7days
Transfuse 1 unit of platelets over 20-30 minutes
When is plasma given?
Give ABO compatible but D group does not matter
Give MB treated plasma to children (non-UK sourced)
How is plasma given?
AB plasma can be given to all groups as it has no anti-A/B antibodies but it is in short supply
No need to cross match but does take 30-40 minutes to thaw
Transfuse 1 unit over 20-30 minutes
What are the indications and triggers for transfusion?
Major blood loss (>30% blood volume loss)
Peri op (critical care) (Hb<70g/L vs 80g/L)
Post chemo (Hb <80g/L)
Symptomatic anaemia (IHD, breathless, ECG)
How do you monitor transfusion?
Check Hb pre transfusion and after every 1-2 units
1 unit RBC gives a Hb increment of 10g/L in a 70-80 kg patient
Transfusion to above 100g/L is rarely required, unless symptomatic or severe cardiac/respiratory disease etc.
What is MSBOS?
Maximum Surgical Blood Ordering Schedule (MSBOS)
How does MSBOS work?
MSBOS is based on negotiation between surgeons and
transfusion lab about predictable blood loss for ‘routine’ planned
Surgery.
Some operations rarely need blood – e.g: gall bladder op
Some operations always need blood – e.g: aortic aneurysm repair
Junior doctors / nurses doing pre-admission clinics have some idea
what is normal. Have to be flexible if non-standard surgery or
special patient requirements (e.g: bleeding disorder)
How do you do MSBOS?
- G&S
2. ALWAYS CROSSMATCH UP FRONT IF RBC ANTIBODIES PRESENT
Why should a G&S be done?
GROUP AND SCREEN before operation: then if no antibodies present, do not cross-match blood, but just save sample in the fridge
If unexpected need for blood, can provide it within 10 minutes (by Electronic Issue, as no antibodies present)
Can own blood be used?
Pre-operative autologous deposit
Donate own blood before planned operation
Not in the UK (futile, no net gain & doesn’t avoid problems of wrong blood or bacterial contamination)
Intra-operative cell salvage
Yes - Collect blood lost during surgery: centrifuge, filter, wash & re-infuse it
Most UK surgical and obstetric units can do this
Post-operative cell salvage Collect blood lost post-op into wound drain – filter & re-infuse Mainly orthopaedic (knee surgery)
What are the special requirement bloods?
CMV negative
Irradiated
Washed
What is CMV negative blood?
only required for intra-uterine and neonatal transfusions (new guidance 2012). Also for elective transfusion in pregnant women (baby in-utero is exposed to maternal transfusion)
What is irradiated blood?
required for highly immunosupressed patients, who cannot destroy incoming donor lymphocytes: which can cause (fatal) transfusion associated graft versus host disease (TA-GvHD)
What is washed blood?
red cells and platelets are only given to patients who have severe allergic reactions to some donors’ plasma proteins
What is the transfusion indicator/ trigger for platelets?
Massive transfusion (Aim plts >75x109/L)
Prevent bleeding post chemo (if <10x109/L or <20 if septic)
Prevent surgical bleed (<50x109/L or <100 if critical site like eye or CNS)
Platelet dysfunction and active bleeding
Who needs to know about a plt transplant?
Haematologist
When are Plts contraindicated?
Heparin-induced Thrombocytopenia Thrombosis (HiTT)
Thrombotic Thrombocytopenic Purpura (TTP)
How much does one unit of plts do?
One unit of platelets is an adult treatment dose: usually raises platelet count by 30-40 x109/L
What is the transfusion indicator/ trigger for FFP?
Massive transfusion (Blood loss > 150mL/min)
Disseminated intravascular coagulopathy (DIC) (with bleeding)
Liver disease + risk (PT ratio >1.5x normal)
Rarely - coagulation factor replacement where factor concentrate not available
What is in FFP?
Fresh frozen plasma contains all clotting factors
What is the impact of 1 unit of FFP?
The adult dose is 15mL/kg
1 unit FFP contains 250mL = adult dose is 4-6 units
What can you not use FFP for?
FFP is not the treatment of choice to reverse warfarin: PCC (prothrombin complex concentrate) is (IX, II, X & bit of VII)
How do you take blood?
Identify patient using wristband
label sample bottle at bedside
Ask them to state their name and date of birth
Never use addressograph labels on blood sample
How do you label a blood bag?
A blood bag with a compatibility label attached
All the information on the blood bag label is bar-coded as well as eye readable
