Heme Flashcards
How are the mechanisms of unfractionated heparin and LWMH the same? Different?
Both bind ATIII
heparin-ATIII inhibits thrombin and Xa equally
LMWH-ATIII preferntially inhibits Xa
What are the two types of HIT?
type I: mild, caused by platelet aggregation
type II: severe, caused by activated platelets that adhere, aggregate, and forms clots
What are the vitamin K-dependent clotting factors affected by Coumadin?
II, VII, IX, and X
protein C and S
How does DDAVP improve hemostasis?
increaes plasma levels of vWF and factor VIII
What does cryoprecipitate contain?
vWF, factor VIII, factor XIII, and fibrinogen
How should subsequent transfusion be managed when a patient has received emergency release whole blood?
After two units, the patient should continue to get type O blood because they will accumulate anti-A and anti-B antibodies.
How does recombinant factor VII facilitate hemostasis?
It directly activates factor X on activated platelets (independent of factors VIII and IX) and causes a “thrombin burst” and a stable fibrin clot
What are the three pedominant roles of vWF in hemostasis?
binding platelets to the subendothelium (via GPIb)
binding activated platelets to each other (via GPIIb/IIIa)
stabilizing carrier for inactive factor VIII
What are the three types of von Willebrand’s disease?
type 1: mild deficiency of normal vWF
type 2: mutant vWF (mostly affecting multimerization)
type 3: severe deficiency of normal vWF
What type of von Willebrand’s disease is responsive to ddAVP?
type 1
What is the primary activator of factor X on the platelet surface?
complex of factors VIII and IX
How does platelet aggregation occur?
GPIIb/IIIa receptors are exposed on activated platelets and crosslinked by vWF and fibrinogen
What is the role of factor XIII in coagulation?
cross-polymerization of fibrin to form a firmer clot
What is the role of factor V in coagulation?
co-factor for factor Xa to achieve thrombin activation
What factors limit clot extension?
tissue factor pathway inhibitor blocks tissue factor actiation of factor X
protein C (and co-factor protein S) inactivate factor Va and factor VIIIa
tPA initiates fibrinolysis
Why might patients with hemophilia A fail to respond to factor VIII infusion? How can they be managed?
30% will develop a neutralizing antibody
can treat with recombinant factor VII, IVIG, plasma exchange
What are the indications for FFP?
factor deficiency
reversal of coumadin
ATIII deficiency
hereditary angioedema (if C1-esterase inhibitor unavailable)
massive transfusion
Can TXA be used in patients with hemophilia A?
Yes, but only documented to be effective with minor bleeding
What kinds of bleeding are best treated by recombinant factor VII?
bleeding confined to a few localized sites, not diffuse bleeding
How long are factor VIII levels supplemented after surgery in patients with hemophilia A?
2-4 weeks
What part of the hemoglobin molecule is affected by sickle cell anemia?
beta globin chain
What are the four kinds of sickle cell crises?
vaso-occlusive
splenic sequestration
aplastic (usually parvovirus B19)
hemolytic (usually with G6PD deficiency)
What is acute chest syndrome? How is it treated?
New infiltrate and pulmonary symptoms similar to PNA often following a vaso-occlusive crisis
Treat with antibiotics, bronchodilators, and exchange transfusion
What are the pre-operative transfusion goals for sickle cell anemia?
Hgb > 8
Hgb A fraction > 40%
What are the anesthetic considerations particular to sickle cell anemia?
maintain O2 content
maintain normothermia
avoid acidosis
avoid touriquet use
avoid venous stasis
avoid hypovolemia
