Hematologic System Flashcards
How are RBCs processed to reduce the chance of febrile transfusion reactions and alloimmunization?
leukoreduction
Why should sodium bicarbonate be given to treat an acute transfusion reaction due to ABO incompatibility?
to alkalinize the urine and prevent hemoglobin precipitation in the renal tubules
What alternative anticoagulants can be used in a patient with HIT? Which are better in patients with renal and/or hepatic failure?
fondaparinux - renal metabolism
argatroban - hepatic metabolism
bivalirudin
What is Humate-P?
factor VIII and vWF concentrate
Which drugs can cause a positive Coombs test (drug-induced hemolysis)?
penicillin
2nd and 3rd generation cephalosporins
alpha methyldopa
procainamide
How do you determine the volume of RBCs to transfuse to reach a target hct?
RBC volume = (Hctinitial - Hcttarget) x BV
HctRBC
BV: blood volume
HctRBC: 60% or 0.6
How are RBCs processed to reduce the chance of GVHD?
irradiation
Is activation of the extrinsic or intrinsic pathway usually the initiating step for fibrin formation?
extrinsic pathway
How much factor VIII activity is needed prior to surgery?
50% for minor surgery
100% for major surgery
Which factors are exposed/released upon platelet activation?
GP IIb/IIIa receptors are exposed on the platelet surface
Thromboxane A2 and platelet activating factor (PAF) are released
What is the “two-hit” hypothesis of TRALI?
hit 1: sequestration of neutrophils in the lung (causing transient leukopenia)
hit 2: activation of reipient neutrophils by donor antibodies
How can factor VIII levels be increased in a patient with hemophilia A?
Factor VIII concentrate: 40 u/mL
cryoprecipitate: 5-10 u/mL
FFP: 1 u/mL
ddAVP: increase production to 2-4x baseline levels
What is the target of the antibodies that cause HIT?
hepain – platelet GP 1b complexes
*causes thrombosis, platelet consumption, and thrombocytopenia
Which anticoagulant is recommended for patients with HIT who need CPB?
bivalirudin
What is the risk of infection due to blood transfusion for HIV? HepB? HepC?
HIV and HepC: 1 in 2,000,000
HepB: 1 in 200,000
What is the mechanism of febrile transfusion reactions?
recipient antibodies directed against donor leukocytes
Which are vitamin K-dependent clotting factors?
Factors 2, 7, 9, and 10
Protein C and S
What are the classic lab findings in DIC?
low platelets
elevated PT/INR and PTT
decreased fibrinogen
increased D-dimer
How much would transfusing one unit (a six-pack) of platelets increase the platelet count?
30-60k
What is the typical timecourse of TRALI?
onset within 2 hours of transfusion
resolution within 48 hours of transfusion
Which receptor interaction causes platelets to adhere to a damaged vessel?
GP 1b on platelets adheres to vWF that is bound to exposed collagen on the damaged endothelium
What are some common precipitating factors for DIC?
sepsis
cancer
retained placenta, fetal demise, amniotic fluid embolus
burns, trauma
transfusion reaction
MH
How are RBCs process to reduce the chance of anaphylaxis in a patient with IgA deficiency?
washed
Which coagulation pathways are monitored with PT/INR? PTT? ACT?
PT/INR: extrinsic and common
PTT: intrinsic and common
ACT: intrinsic and common
Where is plasminogen made? tPA?
plasminogen is made in the liver and incorporated into fibrin clots
tPA is made in the endothelium and released with endothelial damage
How do you calculate maximum allowable blood loss?
MABL = (Hctinitial - Hctfinal) x BV
Hctinitial
BV: blood volume
Why are the intrinsic and extrinsic pathways so named?
Extrinsic refers activation of coagulation in the extravascular space (i.e., by exposed tissue factor on damaged endothelium)
Instrinsic refers to activation of coagulation in the intravascular space
Why does massive transfusion often cause a metabolic alkalosis?
citrate in the blood products is converted to bicarbonate by the liver
What distinguishes the three type of von Willebrand Disease?
vWD type 1: low vWF -> give ddAVP
vWD type 2: mutant vWF -> DON’T give ddAVP
vWD type 3: VERY low vWF -> ddAVP ineffective
What is contained in cryoprecipitate?
fibrinogen
vWF
factor 8
Which receptor interaction allow platlet aggregation?
GP IIb/IIIa receptors for extensive crosslinks with fibrin
Which anticoagulants are direct thrombin inhibitors?
bivalirudin
argatroban
dabigatran
Which anticoagulants are factor Xa inhibitors?
fondaparinux (binds to ATIII)
rivaroxaban
apixaban
How does clopidogrel affect platelet function?
blocks the ADP (P2Y12) receptor and prevents expression of GP IIb/IIIa on the platelet surface
How do abciximab and eptifibatide affect platelet function?
blocking GP IIb/IIIa receptors
Why are patients with sickle cell anemia anemic?
sickled cell are removed by the reticuloendothelial system after 10-20 days instead of the usual 120-day RBC lifespan
What are the crises of sickle cell anemia patients?
- aplastic crisis: folate deficiency or viral infection affecting the bone marrow
- sequestration crisis: hypotension due to massive blood accumulation in the spleen
- hemolytic crisis: in patients with G6PD deficiency and sickle cell anemia
- vaso-occlusive crisis: causing pain due to micro and macro infarcts (i.e., acute chest syndrome)
Which conditions promote sickling?
Anything that decreases SvO2
- increased VO2: shivering, fever, increased metabolic rate
- decreased CO
- decreased SaO2
- decreased Hgb (or right-shifted)
How does hydroxyurea help patients with sicke cell anemia?
as a long-term treatment, it increases fetal hemoglobin levels
How should hgb be optimized pre-operatively in sickle cell patients?
transfuse to a hgb of 30 (regardless of the SS fraction)
Which coagulation factors are not made exclusively in the liver?
factor III (a.k.a. tissue factor): endothelium
vWF: endothelium
factor VIII: endothelium and liver sinusoidal cells
