blood transfusions Flashcards
what are the steps in getting the blood
what are ABO groups determined by
- antigens (sugars) on the red cell membrane.
- naturally-occurring antibodies (IgM) in the plasma.
consequence of ABO incompatible blood test
massive INTRAVASCULR
haemolysis
potentially fatal
proportion of RhD +ve patients
85%
what can different rhesus statuses recieve
+ve :
* RhD -ve red cells
* RhD +ve red cells
-ve :
* RhD -ve
* because make immune anti-D if exposed to +ve red cells - this is very immunogenic -> more likely to make other Ab
summarise immune anti-D Ab
Are IgG (so cross the placenta)
Do not cause direct agglutination of RBCs
Cause delayed haemolytic transfusion reaction
There are some other Rh antigens e.g., C, c, E and e
what are the other Ag and are they tested for
Kell (K), M, N, S, Duffy (Fy), Kidd (Jk),
only match for these if patient has corresponding antibody (or occasionally in certain other situations)
Kell – important in maternity
Duffy and Kidd – delayed haemolytic reaction – important if chronically dependent on transfusion
who can get Rh -ve blood
anyone
short supply
what happens if Rh-ve get +ve blood
happens in emergency/shortage
no acute problem
induce anti-D formation - picked up in lab next time
-> get RHd -ve blood
save Rhd -ve blood for people of childbearing potential because can cause:
* haemolytic disease of newborn
* severe fetal anaemia
* hydrops fetalis (heart failure)
when do you test blood group
before every transfusion, even if it has been done many times before
how is blood group tested
Use known anti-A and anti-B and anti-D reagents against patient’s RBCs ** “forward group**”
reagents are monoclonal Ab and are saline reacting at room temp
And “reverse group”: known A and B group RBCs against patient’s plasma (IgM antibodies)
this is internal control
newborns have weak reverse gp because Abs not formed yet
if been transfused with blood that is not the same group as own (group O blood to a group A patient for example) will have a dual population of red cells (A and O) and the reverse group will only have anti-A
what is Ab screen for
because cant test all RBC Ag
pts have Ab from exposure to other cells eg in pregnancy and transfusion
see what Ab the patient has and transfuse RBC w/o that ag
to prevent delayed haemolytic transfusion reaction (>24hr post) - extravascular haemolysis in the spleen
summarise automated blood grouping and Ab screening
Bar coded samples (id correct throughout – no mix up)
Computer interfaces – reduces transcription errors
Robotic sample and reagent handling
Liquid level sensors (? failed to add reagent)
Reading of results by image analysis
Interpretation of results from digital photographic image
Download to patient record
how do you do an Ab screen
2 or 3 reagent red cells containing all the important red cell antigens
incubate the patient’s plasma and screening cells using indirect antiglobulin technique
Immune antibodies are of variable strength and need help to bind to the antibody screening cells.
Low ionic strength saline brings the cells closer together and the mixture is incubated at 37C
An antiglobulin reagent (anti-human IgG) is added to show if there is an antigen-antibody interaction
If there is an immune antibody the red cells will clump – POSITIVE SCREEN
If there is no antibody the red cells stay in suspension – NEGATIVE SCREEN
what is electronic issue
selection and issue of red cell units
where compatibility is determined by IT system,
without physical testing of donor cells against patient plasma
why do electronic cross match
Quicker
Fewer staff
No blood on stand by
Issue blood remotely
Better stock mx
can even release blood from a fridge on another site – this is called remote issue.
who is not suitable for electronic cross match
anomalous blood groups,
those with red cell antibodies
those who have only had a blood group tested once.
what is serological cross match
-
FULL CROSSMATCH
INDIRECT ANTIGLOBULIN TECHNIQUE
takes at least 40 min - not suitable for emergency -
IMMEDIATE SPIN (SALINE, ROOM TEMPERATURE)
Incubate patient plasma and donor red cells for 5 minutes only
and spin, will detect ABO incompatibility only
used for emergency - prevent immediate but not delayed haemolytic reaction
what are the 3 pillars of patient blood management
- optimise haemopoiesis - identify pre-op anaemia and treat
- min blood loss and bleeding
- harness and optimise physioological tolerance of anaemia
what is MSBOS
maximal surgical blood ordering schedule
agreement about predictable loss
some operations rarely/always need a lot of blood
Blood allocated to a patient, if not used are taken back into stock… repeatedly. – as long as back within 30 mins can reissue up to 3 times
when do you transfuse red cells
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.
when do you transfuse platelets
Want to keep plt count above 50
If septic – want above 20
Head, neck, eye surgery – want to keep plt count above 100
Plt dysfunction or immune cause – only give if active bleeding
CI in: Haparin induced thrombocytopenia thrombosis And TTP
If having interventional procedure – give plts when do the procedure, not before because they will have consumed the patients. Give plts as knife goes to skin
One unit usually raises platelet count by 30-40 x109/L
FFP indications and dose
when do you give cryoprecipitate
More fibrinogen than FFP
If low fibrinogen – give CPTT
2 pools is an adult dose
Raise fibrinogen by 1g/L
