Transfusions Flashcards
4 blood groups present on the surface of RBC
A, B, AB, O (absence of A or B)
when do people start developing antibodies against A/B antigens?
by 12 months antibodies develop NATURALLY. this differs from other immune responses as usually antibodies develop after you have been exposed to them
expain which blood groups develop which antibodies
group A - B antibodies group B - A antibodies AB - no antibodies O - A and B antibodies RH+ - no RH antibodies RH- - RH antibodies
what will happen if you give A blood to someone who is group B
intravascular haemolysis due to ABO mismatch. IgM anti A antibodies in the B blood will bind to the A antigen in the A blood. Red cell haemolysis occurs. free Hb enters the blood stream (very vasoactive)
Biochemically what happens in a transfusion reaction, and what can this cause
increase bilirubin, lactate dehydrogenase (LDH), positive coombs (DAT) test, haptoglobin decrease (which means markers of haemolysis are positive)
free Hb in the blood and urine (black urine), go into shock, DIC, fatal in 1/3 of cases
How can ABO mismatched transfusions be avoided
Only give blood when indicated
rigarous ID checks
only give when a patient can be monitored
stop transfusion immediately if patient starts to react
avoid transfusions after midnight unless strong clinical indication (major haemorrhage and end organ failure)
Signs of an ABO mismatch
mainly - pyrexic and maybe rigors
Shock - hypotensive, tachycardic, sweating, pain (abdo, back, flank, chest)
may get a local reaction at the site, oedema and breathing tachypnoeic (lung crackles)
How to manage an ABO mismatch
stop transfusion - keep blood product and check pack with ID, preserve donor blood bag and send down to blood bank.
start resuscitation (A-E)
get senior support
maintain IV access, as you will need to give saline.
monitor vital signs
tests - FBC, metabolic panel, Urinalysis, Haemolysis panel and LDH, Coombs test.
Monitor electrolyes and protect the heart, be prepared to do urgent haemolysis
widespread haemolosis may require vasopressor support
DIC - treat supportively
Differentials of an ABO mismatch
Bacteraemia of the blood (though this more common in platelets)
Acute deterioration of condition
Anaphylaxis
oedema and breathing difficulties - fluid overload (no fever, hypotension etc)
Non ABO blood group systems
main one is rhesus. also duffy, jka, kale?
How do non abo blood groups system differ from the ABO system
delayed rather than acute reaction
do not commonly naturally make antibodies against them (need to be exposed e.g. blood transfusion or pregnancy)
involved in anaemia of the foetus
if patient has antibodies, then it takes longer for the lab to cross match blood, and they have to be crossmatched. no antibodies (just ABO) can be prescribed electronically but these cant, so there is a clinical delay in transfusion of these patients
what happens in a delayed transfusion reaction
non ABO system (e.g. rhesus)
+ve infusion in a -ve patient will cause an immune reaction against the antigens. IgG antibodies made, if body comes in contact with that antigen again, the antibody will bind to it, picked up by cells in the reticular endothelial system, taken to the spleen and broken down (outside of the vascular system)
explain HDFN
mother is RHD-ve, has made a anti-D antibodies. Baby is RHD+ve. As the anti-D antibody is IgG it can cross the placenta and bind to the babies RHD antigens, causing haemolysis. this can cause anaemia of the foetus and can cause still birth
how is HDFN prevented
Pregnant ladies have group and save early on in pregnancy to screen for antibodies
if RHD-ve given prophylaxis anti-D during sensitizing events of the pregnancy (delivary). it is thought that this prevents the woman making antibodies of her own, and masks the antigens in the babies system
How are RBC stored
at 4 degrees Prevent bacterial growth), kept for 35 days
how quickly should RBC be transfused
once out the fridge have to be transfused within 4 hrs
how are RBC treated in high risk patients
in immunodeficient patients, RBC may be irradiated to inactivate any remaining lymphocytes prevent transfusion related graft vs host disease
(though also damages red cells)
who gets irradiated RBC
IN ELECTIVE SITUATIONS
any intrauterine, if recieving blood from a first or second degree relative, immunosuppressed (eg ca such as Hodgekins lymphoma), neonatal
who gets CMV negative blood
IN ELECTIVE SITUATIONS
can be fatal to babies, so pregnant ladies and newborn/prem babies
what is CMV negative blood
someone who has never had cytomegalovirus wont have developed any antibodies against it, so is considered CMV negative (only 15% of people at 40 will be CMV neg)
when are red cells indicated
in major haemorrhage (usually along with other products) anaemia causing end organ failure with a hb <100 (e.g. heart failure, unstable angina, much more likely if hb lower than 60) Symptomatic anaemia (with no end organ failure) <80 where there is no alternative to a transfusion (usually get symptoms between 80-100) if below 60 then should definitely be transfusing bc risk of end organ failure is so much higher
when are you not thinking about transfusion
Hb over 100
Hb over 70 and no/minimal symptoms
when an underlying cause for anaemia is present and can be treated without resorting to blood transfusion (UNLESS end organ failure present/ likely to become present (under 60))
treatable causes of anaemia
Iron deficiency - iron infusion B12/folate inflammation e.g. rheumatoid Renal failure - EPO Drugs e.g. myelosuppressives DONT TRANSFUSE UNLESS END ORGAN FAILURE
how many RBC transfusions are not indicated
1/3
