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Anticoagulation

Pharm (Final)

QuestionAnswer
Describe the 4 steps of basic hemostasis. 1)adhesion of platelets to damaged vessel wall, 2)activation of platelets, 3)aggregation of platelets-- fibrinogen links platelets together, but clot still water soluble and fragile, 4)production of fibrin (secondary hemostasis)
What is the mechanism of action of heparin? (4 parts) 1)binds to antithrombin, 2)increases its ability 1000X, 3)inactivates thrombin IIa, factors X, XII, XI, IX, 4)inhibits platelet function
Which clotting factors are affected by heparin (in order of most affected to least affected)? X, XII, XI, IX
What is antithrombin? endogenous anticoagulant
True or False: Heparin is a mixture of different molecular weights. True
Only ______ of heparin binds with antithrombin. 1/3
Where does heparin come from? bovine lung, bovine or porcine GI mucosa
Heparin is endogenous in what parts of the human body? basophils, mast cells, and liver
Where does the "Hep" in heparin come from? b/c heparin is found endogenous in the liver
Define 1 unit of heparin. volume of solution that will prevent 1mL of sheep's blood from clotting for 1hr after the addition of 0.2mL CaCl
Heparin is (highly or poorly?) lipid soluble. poorly
Heparin (can or can't?) cross the placental barrier. can't (poorly lipid soluble)
What is heparin's route(s) of admin? IV or subQ
Why should heparin not be given IM? risk of hematoma
True or False: The duration of heparin increases as dose increases, in a linear pattern. False (non-linear)
How is heparin eliminated? not fully understood-- some in the urine
What is ACT? activated coagulation time-- monitoring of heparin affect
ACT measurement can be affected by... hypothermia, hemodilution, thrombocytopenia, presence of contact activation inhibitors (aprotinin), preexisting coagulation deficiencies (hemophilia, von willebrands, etc)
A baseline/control ACT should be _______sec. 90-120sec
For bypass, the ACT should be ______sec. >300sec
When is ACT measured? 1)prior to heparin admin (baseline), 2)3min after admin, 3)every 30 min
If a pt is not achieving ACT>300sec after redosing, what should you do and why? give FFP (may not have enough endogenous antithrombin)
Why do we monitor ACT every 30 min? 1)variation between pts in sensitivity to heparin, 2)variation btwn pts in rate heparin is metabolized
What are 6 clinical uses of heparin? 1)venous thrombosis, PE, 2)prevention of mural thrombosis after MI, 3)unstable angina, acute MI, 4)prevention of coronary artery rethrombosis after thrombolysis, 5)prevention of thrombosis during CBP, 6)treat fetal growth retardation in pregnancy
What is the most severe side effect of heparin? hemorrhage
Pts have a greater risk of hemorrhage w/ heparin if they are also taking... aspirin
Avoid heparin in _______________ surgery due to risk of hemorrhage. intraocular or intracranial
True or False: Heparin should be given before an epidural, spinal, or axillary block to prevent clotting. False: Avoid heparin d/t risk of hematoma on spinal cord
True or False: Heparin can cause thrombocytopenia. True
Mild thrombocytopenia is a platelet count <__________. <100,000
How often does mild thrombocytopenia occur d/t heparin use? 30-40%
Severe thrombocytopenia is a platelet count <__________. <50,000
How often does severe thrombocytopenia occur d/t heparin use? 0.5-6%
True or False: Severe thrombocytopenia can be life threatening. True
What CV effects can be caused by heparin? decrease in MAP/PAP, decrease in SVR (relaxant effect on smooth muscle)
True or False: Although giving Ca+ can reverse the CV effects of heparin, iCa+ levels are not affected by heparin admin. True
True or False: Repeated heparin can cause a dec. antithrombin activity and may require a greater dose of heparin. True
What is the reversal for heparin? protamine
True or False: Protamine, by itself, is an anticoagulant. True
What is protamine? Where is it found? positively charged protein; salmon sperm
What is the mechanism of action of protamine? combines w/ the negatively charged heparin, resulting complex has no anticoagulation effect
How is protamine removed? the reticuloendothelial system
What is the reversal dose of protamine? 1mg per every 100 U of heparin circulating
What are some CV effects of protamine? hypotension, tachycardia, histamine release
How can you minimize the CV effects of protamine? (2 ways) give over 5 min, give peripherally to dilute the complex that causes histamine release in the lungs
What pulmonary effect can protamine cause? How? pulmonary hypertension: thromboxane release causes pulm. vasoconstriction, pulm. HTN, and bronchoconstriction
True or False: Protamine is associated with allergic reactions? true
Which pts are most at risk of a protamine allergic reaction? pts taking NPH insulin (contains protamine), and pts allergic to shellfish
What should you use to pretreat pts at risk of a protamine allergic reaction? histamine blockers and steroids
What are 3 antiplatelet medications? aspirin, Plavix, ticlid
What is the mechanism of action of aspirin? interfere w/ the activity of cyclooxygenase and with the release of ADP, which interrupts the synthesis of thromboxane A2, thus causing impaired platelet aggregation
What is the duration of action of aspirin? the whole life of the platelet (8-12 days)
Do you need to stop aspirin prior to neuraxial anesthesia? no
What is the mechanism of action of Plavix and ticlid? block ADP receptors (irreversibly) on the platelets which inhibits the platelet activation AND aggregation for the life of the platelet
Plavix needs to be stopped ________ days before surgery. 7
Ticlid needs to be stopped ________ days before surgery. 14
What is the new FDA warning about Plavix? may have decreased function with given with omeprazole
What are 3 anti-fibrinolytics? 1)aprotinon/Trasylol, 2)aminocaproic acid/Amicar, 3)Tranexamic acid
What is the mechanism of action of aprotinin? 1)inhibits plasmin (a more stable clot is formed b/c the fibrin breaks down slowly) and bleeding is decreased; 2)may protect platelets, 3)inhibits inflammatory response to CPB by preventing the movement of leukocytes through the vascular lining
What does plasmin do normally? breaks down the fibrin clot
What are 2 clinical uses of aprotinin? 1)"redo" cardiac operations, 2)prevention and treatment of hemorrhage during surgery
What is 1 contraindication of aprotinin? if a pt has known or suspected exposure to aprotinin within the last 12 months
Is aprotinin naturally occurring or synthetic? naturally occurring
Is amicar naturally occurring or synthetic? synthetic
What is the mechanism of action of amicar? forms a reversible complex with plasminogen which prevents fibrinolysis
What are some clinical uses of amicar? decreases post-op bleeding and dec. needed transfusions (CPB, scoliosis, orthotopic liver transplant, lower urinary tract surgery)
What is a contraindication of amicar? renal or urethral bleeding (may lead to obstruction of the ureter)
Is transexamic acid naturally occurring or synthetic? synthetic
What is the mechanism of action of transexamic acid? prevention of the interaction btwn plasminogen and fibrin