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Anticoagulation
Pharm (Final)
| Question | Answer |
|---|---|
| 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 |
Created by:
lindseymontgomery
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