Tranfusion medicine Flashcards
What kind of antibodies are the antibodies aagainst the ABO blood groups?
IgM
How does IgM bound to ABO to cause hemolysis within seconds?
triggers the complement cascade - phagocytic cells - coagulation from free hgb - systemic inflammation and scavenger NO
(intravascular hemolysis)
can kill you
How is the IgM activity different from IgG bound to blood cells?
doesn’t trigger complement cascade, but will stay on the RBC until it gets to the spleen hwich will then take it out. NO systemmic reaction and it won’t kill them.
(extravascular hemolysis)
Where else in the body are the ABO antigens?
on RBCs
on vascular endothelium
platelets
epithelial surfaces
soluble forms just floating in our blood, saliva, milk, urine, meconium, feces, etc.
What are some diseases we see from ABO incompatibility?
hemolytic transfusion reactions
solid organ transplantation (hyperactue rejection)
mild hemolytic disease of fetus and newborn (this is Igm antibodies and very few will get through the placenta, so it’s not as severe)
What is the most common presenting symptom of an ABO incompatible RBC transfusion?
fever
What are some other symptoms?
feeling of dread flushing pain at infusion site low back and flank pain chest abd pain n/v shock SOB, hyperventilation, cyanosis
THere are multiple antigens in the Rh group, what is the most important one?
D antigen
Why do we care about the Rh group?
it’s the most immunogenic blood group outside of ABO
What kind of antibodies do we have against D?
IgG
note - can only happen after a previous exposure
WHy do Rh antibodies cause a more severe hemolytic disease of the newmorn than the ABO antibodies?
This is IgG instead of IgM, so it’s all going through the placenta.
How do you track hemolysis in a fetus?
dopplers of the middle cerebral artery (higher flow suggests anemia)
used to need to use a Liley curve to track bilirubin in the amniotic fluid by gestational age
What do you do for treatment of these babies?
intrauterine transfusions
What does “weak D” mean?
there are lower levels of D antigen on the surface of RBC (normal antigen, but not highly expressed)
low enough levels that when we test the patient, we can’t tell in all cases. So we might call them D negative, which can be dangerous
What does “partial D” mean?
there are mutations in the antigen structure, so some will be missed because our lab test may use a monoclonal antibody against part of the normal antigen they don’t have
so these people will also be called D negative
Why is this an issue particularly for the partial D patients?
They are called D negative, which they sort of are because their D might be different enough from normal D that if they did receive D+ blood they could develop an antibody against it
Do we actually know that rhogam won’t work after 72 hours?
nope - prison story
so just give it even if it’s late
How many antigens in the Kell system?
24
Why is Kell important?
- it will cause immediate or delayed hemolysis
- Kell alloantibodies are very hard to detect, so you wouldn’t be concerned about it unless you did a special test or you saw a Kell- person received a Kell+transusion in the past
Most people are Kell ____
negative
Why is a pregnant mom getting Kell antibodies during pregnancy an even bigger deal than ABO and Rh?
Kell antigen is expressed on the placenta very early and causes suppression of erythropoiesis
The Mcleod phenotype (missing the XK protein that goes with the Kell on RBC membrane) is associated with what two diseases?
chronic granulomatous disease
Duchenne’s
WHy is this important to think about for these patients?
they can’t get regular blood - so they need their own stored for them
Why is the Kidd blood group system clinically significant?
it’s famous for disappearing and reappearing and can cause a roaring delayed hemolytic transfusion with amnestic response leading to intravascular hemolysis
Duffy is a six antigen system that causes a problem in what patient population?
Sickle cell patients; because duffy antigen is the receptor for plasmodium vivax. So basically all caucasians are duffy positive and african americans (especially sicklers) are mostly negative
and caucasians tend to give blood more often
WHat is the P-antigen group?
it’s the receptor for parvovirus B19
After a viral illness, kids in general can develop an autoantibody against he P-antigen and develop what?
paroxysmal cold hemoglobinuria
antibody binds in the extremities and then activate complement and hemolysis when they reach the warm body core
How do you test for paroxysmal cold hemoglobinuria?
the Donath-Landsteiner test
basically intubate three tubes at different temperatures and positive test has lysis at 37 C
How does paroxysmal cold hemoglobinuria present?
rarely paroxysmal, precipitated by cold and it’s not necessarily hemoglobinuric
kids usually presenting with an acute anemia following viral infection
How does the I and i work on RBCs - how do we all have both?
i is the long carbohydrate on young RBCs
as the RBC matures, the carbohydrate folds and it becomes I
Anti-I antibodies are associtaed with what infection
mycoplasma in adults
Anti-i is associated with what infection?
mono in kids
“Type” determines what?
the ABO
the “screen” determines what?
presence of antibodies against commonly clinically important RBC antigens (Kidd, Kell, Rh, etc.)
What is “front type”?
you mix patient’s RBCs with anti-A and anti-B monoclonal antibodies and see if ti reacts
What is the “back type”?
mix the patient’s PLASMA with known RBCs to see if it reacts
Since anti-A and anti-B are IgM, how long will it take for agglutination to occur on these tests?
happens immediately
What type of test is used for the screen?
indirect antiglobulin test
take plasma, add RBCs with known antibodies, add anti-human globulin (anti-Fc) or Coomb’s reagent
this will lead to agglutination if the plasma had antibodies against the RBCs that were added
How long does a negative type and screen take?
30-60 min
How long does a positive type and screen take?
1-4 hours or maybe more
How long will a type and screen last (when would you need to repeat it)?
72 hrs
What is the cross match?
Patient’s plasma with donor RBCs
just to check one more time that there aren’t antibodies that were missed
What is the electronic cross match?
scan the blood batch and patient’s MRN and the computer will tell you if it’s compatible if they have no hx of unexpected antibodies and currently negative antibody screen
this means blood is ready immediately, but there still continues to be a small risk that patient may have an antibody against a rare antigen, which is why nurse needs to be in the room to watch for a reaction
The direct antibody test looks for antibody directly bound to the surface of the RBC in vivo. So in this setting, what do we use the DAT for?
To diagnose a hemolytic reaction
order it especially in the ED when someone’s been dropping hemoglobin and they’re a little symptomatic with relatively recent hx of a transfusion
What’s the volume of blood in a RBC unit?
250-350 ml with 200-250 ml or RBCs
How much will hematocrit increase and hemoglobin increase after an RBC?
Hematocrit should increase 3%
Hemoglobin should increase 1%
If that 3:1 ratio is off after a transfusion, what does that tell you?
volume status
Wha is the transfusion indication for RBCs?
to correct anemia and increased O2 delivery
Without co-morbidities, what hemoglobin is the cutoff for transfusion?
7
If they do have co-morbidities, what hemoglobin is the cutoff?
you can still use the 7 or 8-10; depending on the study you look at
What are some co-morbidities that you would want to use 8 as the cutoff?
cardiac disease tachycardia respiratory failure bone marrow failure hematologic disease cerebrovascular disease
Neonates should get a transfusion with a hgb less than?
13 (although there’s really no data for this - we’re conservative with babies)
People with cyanotic heart disease should get a transfusion with a hgb less than?
13
WHat’s in FFP?
200-250 ml
400 mg of fibrinogen
1 unit/ml of all the coagulation factors
Which factor in FFP has the shortest half life?
Factor 7; so if they have a coagulopathy, that FFP transfusion will start to not be enough within about 4 hrs because the 7 will degrade in vivo
WHat’s the difference between FFP an FP24?
FFP must be frozen within 8 hrs
FP24 (plasma) is frozen within 24 hrs, containing less factor 5, factor 8, protein S and C
What are the indications for FFP?
INR>1.8
PTT>45’’
What shoudl the dosage of FFP be?
10-20 ml/kg
s 2 units should increase factor levels by 20-30% in a 70 kg person
FFP can be used for emergent reversal of warfarin, but what should you use instead if time permits?
vitamin K
What’s the universal plasma donor?
AB (no antibodies)
A platelet unit from a single donor = __whole blood derived platelet unit.
6 (so consider this when you’re ordering)
One single donor platelet unit should increase platelet count by how much?
25-40,000
What platelet count is sufficient to maintain vascular integrity?
5,000/ul, but about 7000/ul are consumed each day to repair the microvasculature
you should be completely safe at 10,000 as long as they’re still making their own platelets
So when do you transfuse platelets?
<10K for normal patients <20K with mucosal bleed <50 for active bleeding, surgery <50K for infant under 1 mo <100,000 for neuro or ophthalmologic surgery bc bleed would be devastating
WHat does Cryoprecipitate contain?
250 mg fibrinogen vWF Factor VIII Factor XIII Fibronectin
WHat’s the indication for cryo?
mainly a fibrinogen deficiency
What does leukoreduction do?
reduces the # of leuklocytes present in RBC and platelet units in an effort to reduce febrile non-hemolytic transfusion reactions from WBC cytokines
WHo needs to have irradiated blood? Why?
patients with compromised T-cell function
the transfusion of donor lymphocytes can cause transfusion-associated graft vs host disease and start to attack the bone marrow, killing them within 21 days with 100% mortality
What is the risk with using irradiated blood?
it increases the potassium level, so in an infant or a patient with a cardiac arrythmia or hyperkalemic already, this can cause cardiac arrest
