Introduction The coagulation cascade comprises a series of reactions that lead to formation of fibrin, which leads to platelet activiation and clot formation an imbalance of the coagulation cascade can cause thromboembolism and DVT Virchow's triad describes risk factors for thromboembolism and DVT and includes venous stasis endothelial damage hypercoagulable state Orthopaedic surgery predisposes high risk of thromboembolism and certain procedures may require anticoagulation there are many choices of anticoagulants, each has advantages and disadvantages chemical DVT prophylaxis may not be indicated in isolated lower extremity fractures below the knee Overview of Anticoagulants (details below) Overview of Anticoagulants Mechanism Advantage Disadvantage Compression stocking Mechanical No bleeding Compliance ASA Inhibits the production of prostaglandins and thromboxanes convenience IV heparin Enhances ability of Antithrombin III to inhibit factors IIa, III, Xa Reversible IV administration Unfractionated heparin (subcutaneous) Enhances ability of ATIII to inhibit factors IIa, III, Xa Reversible Bleeding LMWH (Lovenox) Enhancing ability of ATIII to inhibit factors IIa (thrombin), III, Xa Fixed dose, no lab monitoring required Bleeding Fondaparinux Indirect Xa inhibitor (works through ATIII) No lab monitoring required Coumadin Affects Vit K metabolism in the liver, limiting production of clotting factors II, VII, IX, X Most effective Difficult to reverse Dextran Dilutional Efficacy Fluid overload Rivaroxaban (Xarelto), Apixaban (Eliquis), Edoxaban (Savaysa) Direct Xa inhibitor Oral Bleeding Dabigatran (Pradaxa) Direct thromBin inhibitor ASA (acetylsalicylic acid) Introduction thromboxane function under normal conditions thromboxane is responsible for the aggregation of platelets that form blood clots prostaglandins function prostaglandins are local hormones produced in the body and have diverse effects including the transmission of pain information to the brain modulation of the hypothalamic thermostat inflammation Mechanism of ASA inhibits the production of prostaglandins and thromboxanes through irreversible inactivation of the cyclooxygenase enzyme within platelets acts as an acetylating agent where an acetyl group is covalently and irreversibly attached to a serine residue in the active site of the cyclooxygenase enzyme. this differentiates aspirin different from other NSAIDs which are reversible inhibitors Metabolism renal Unfractionated Heparin (SQ) Mechanism binds and enhances ability of antithrombin III to inhibit factors IIa, III, Xa Reversal protamine sulfate Metabolism hepatic Risk bleeding HIT (heparin induced thrombocytopenia) Low Molecular Weight Heparin Overview molecular name: enoxaparin trade name: Lovenox, Clexane has advantage of not requiring lab value monitoring Mechanism LMWH acts in several sites of the coagulation cascade, with its principal action being inhibition of factor Xa reversed by protamine Metabolism renal Risk bleeding Fondaparinux Overview trade name: Arixtra has advantage of not requiring lab value monitoring Mechanism indirect factor Xa inhibitor (acts through antithrombin III) Metabolism renal Evidence studies show decreased incidence of DVT when compared to enoxaparin in hip fx and TKA patients Risk highest bleeding complications not to be used in conjunction with epidurals Warfarin Mechanism of anticoagulation inhibits vitamin K 2,3-epoxide reductase prevents reduction of vitamin K epoxide back to active vitamin K vitamin K is needed for gamma-carboxylation of glutamic acid for factors II (prothrombin), VII (first affected), IX, X protein C, protein S Monitoring target level of INR (international normalized ratio) is 2-3 for orthopaedic patients not achieved for 3 days after initiation Reversal vitamin K (takes up to 3 days) fresh frozen plasma (acts immediately) Risk difficult to dose requires the frequent need for INR lab monitoring can have adverse reaction with other drugs including rifampin phenobarbital diuretics cholestyramine Rivaroxaban (Xarelto) Overview others in the same class include apixaban (Eliquis) and edoxaban (Savaysa or Lixiana) mechanism of action of these drugs can be deduced from the name. Rivaro(Identifier)-xa(FactorXa)-ban(inhibitor) Mechanism direct Xa inhibitor Metabolism liver Antidote no current antidote andexanet alpha being investigated Risk bleeding Half-life 8-hours (12-hours for apixaban) urgent surgical procedures delayed until half-life spanned from last dose Dabigatran (Pradaxa) Mechanism reversible direct thrombin (factor IIa) inhibitor Metabolism renal Antidote idarucizumab (FDA approved Oct 2015) Risk GI upset bleeding Tranexamic acid (TXA) Overview an antifibrinolytic that promotes and stabilizes clot formation studies have shown that TXA reduce perioperative blood loss and transfusion in THA and TKA Mechanism synthetic derivative of the amino acid lysine competitively inhibits the activation of plasminogen by binding to the lysine binding site at high concentrations, is a non-competitive inhibitor of plasmin has roughly 8-10 times the antifibrinolytic activity of ε-aminocaproic acid Dosing intravenous 10-20 mg/kg initial bolus dose followed by repeated doses of the initial TXA dose every 3 hours for 1-4 doses 10-20mg initial bolus followed either by an infusion of 1-10 mg/kg/hr for 4-30 hours topical application is as effective as IV sprayed onto open wound at completion of procedure no detectable TXA in the bloodstream after topical application oral adminsitration is as effective as IV 1.95g given 2 hours preoperatively Metabolism <5% of the drug is metabolized biological half-life in joint fluid is 3h, present in tissues for up to 17h Risks systematic review shows no increase in thromboembolic events relatively few adverse reactions have been reported in the arthroplasty literature Herbal Supplements Increased bleeding gingko, ginseng, and garlic have been found to increase the rate of bleeding related to effect on platelets proper history taking can avoid complications Increased warfarin effect (increase INR) omega-3 fish oil affects platelet aggregation and vitamin K dependent coagulation factors Reduced warfarin effect (reduces INR) coenzyme Q10 green tea direct warfarin antagonist (reduces INR) St John's wort increases catabolism of warfarin (reduces INR)
QUESTIONS 1 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Previous Next Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (OBQ18.250) Where in the coagulation cascade shown in Figure A does enoxaparin primarily exert its effects? QID: 213146 FIGURES: A Type & Select Correct Answer 1 A 5% (85/1687) 2 B 2% (40/1687) 3 C 59% (987/1687) 4 D 10% (167/1687) 5 E 24% (400/1687) N/A Question Complexity A Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic (OBQ18.173) Which of the following agents results in blood anticoagulation by exerting inhibitory effects on the factor circled in the color red in Figure A? QID: 213069 FIGURES: A Type & Select Correct Answer 1 Aspirin 2% (46/1859) 2 Fondaparinux 19% (348/1859) 3 Rivaroxaban 9% (162/1859) 4 Tranexamic acid (TXA) 13% (246/1859) 5 Heparin 56% (1032/1859) L 4 Question Complexity A Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 5 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (OBQ13.154) Which of the following medications used for thromboprophylaxis following orthoapedic surgery is a direct inhibitor of factor Xa? QID: 4789 Type & Select Correct Answer 1 Dextran 1% (20/3824) 2 Rivaroxaban (Xarelto) 80% (3045/3824) 3 Coumadin 4% (137/3824) 4 Fondaparinux (Arixtra) 15% (583/3824) 5 Aspirin 0% (17/3824) L 2 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic (OBQ13.208) Which of the following medications works through the competitive inhibition of plasminogen activation? QID: 4843 Type & Select Correct Answer 1 Lovenox 5% (256/5128) 2 Rivaroxaban 7% (372/5128) 3 Tranexamic acid 78% (3982/5128) 4 Fondaparinux 8% (417/5128) 5 Coumadin 2% (78/5128) L 2 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (OBQ12.12) Which of the following pharmacologic agents is associated with the highest risk of bleeding and thrombocytopenia? QID: 4372 Type & Select Correct Answer 1 Coumadin 10% (483/5005) 2 Enoxaparin 11% (528/5005) 3 Unfractionated heparin 75% (3748/5005) 4 Dalteparin 3% (138/5005) 5 Protamine sulfate 2% (77/5005) L 2 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic (OBQ11.168) All of the following are AAOS recommendations regarding prevention of venous thromboembolic disease (VTED) in patients undergoing elective hip and knee arthroplasty EXCEPT? QID: 3591 Type & Select Correct Answer 1 Patients should discontinue antiplatelet agents before undergoing elective hip or knee arthroplasty 9% (220/2376) 2 Aspirin is not approved as a preventative medication for VTED in low risk patients 73% (1731/2376) 3 Neuraxial (epidural, spinal, intrathecal) anesthesia is recommended when possible 8% (198/2376) 4 Routine post-operative duplex ultrasonography screening is not recommended 3% (79/2376) 5 Mechanical prophylaxis mechanisms are recommended in patients with a known bleeding disorder 6% (136/2376) L 2 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (OBQ10.11) Which of the following supplements affects blood clotting through its effect on platelets? QID: 3099 Type & Select Correct Answer 1 Ginkgo 62% (1357/2192) 2 Vitamin D 1% (22/2192) 3 Ephedra 2% (51/2192) 4 St. John's Wort 30% (668/2192) 5 Selenium 3% (74/2192) L 1 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 1 Review Tested Concept Review Full Topic (OBQ09.120) Which drug works by preventing gamma carboxylation in factor X, factor IX, and prothrombin? QID: 2933 Type & Select Correct Answer 1 Warfarin 70% (2148/3086) 2 Heparin 10% (307/3086) 3 Aspirin 1% (26/3086) 4 Clopidogrel 6% (193/3086) 5 Enoxaparin 13% (400/3086) L 3 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 1 Review Tested Concept Review Full Topic (OBQ09.116) Low-molecular-weight heparin has been shown to have an increased rate of which of the following when compared to aspirin, clopidogrel, and compression devices? QID: 2929 Type & Select Correct Answer 1 Pneumonia 1% (8/1320) 2 Fatal pulmonary embolism 3% (40/1320) 3 Inferior vena cava filter placement 1% (12/1320) 4 Renal failure 19% (246/1320) 5 Postoperative hematoma 76% (1006/1320) L 2 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 5 Review Tested Concept Review Full Topic (OBQ08.262) What is the mechanism of action of warfarin? QID: 648 Type & Select Correct Answer 1 Binds to platelets and inhibits their aggregation 1% (10/1799) 2 Inhibits vitamin K-dependent clotting factors 98% (1770/1799) 3 Blocks COX-2 function 0% (7/1799) 4 Unselective COX inhibiter 0% (1/1799) 5 Decreases Anti-thrombin III activity 1% (10/1799) L 1 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic This is an AAOS Self Assessment Exam (SAE) question. Orthobullets was not involved in the editorial process and does not have the ability to alter the question. If you prefer to hide SAE questions, simply turn them off in your Learning Goals. (SAE07HK.56) Figure 33 shows the venogram of a patient who has a long history of alcohol abuse. Warfarin should be used cautiously because of the interaction with which of the following factors? QID: 6016 FIGURES: A Type & Select Correct Answer 1 IV 1% (10/693) 2 V 6% (40/693) 3 VI 1% (7/693) 4 VII 83% (575/693) 5 VIII 8% (54/693) L 2 Question Complexity E Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (OBQ07.212) Protamine functions to reverse the pharmacologic effects of which of the following anti-coagulants? QID: 873 Type & Select Correct Answer 1 Aspirin 1% (12/1319) 2 Clopidogrel (e.g. plavix) 3% (38/1319) 3 Low molecular weight heparin 89% (1172/1319) 4 Warfarin 5% (62/1319) 5 Hirudin 2% (32/1319) L 2 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic (OBQ04.218) Which of the following medications exerts its influence on the clotting cascade by inhibiting the carboxylation of normal clotting factors? QID: 1323 Type & Select Correct Answer 1 Warfarin 86% (1637/1906) 2 Enoxaparin 4% (71/1906) 3 Dalteparin 2% (42/1906) 4 Heparin 4% (76/1906) 5 Hirudin 4% (74/1906) L 1 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 1 Review Tested Concept Review Full Topic
All Videos (1) Podcasts (1) Login to View Community Videos Login to View Community Videos Orthopaedic Summit Evolving Techniques 2020 Evolving Technique Update: Anticoagulants When To Stop & When To Restart - Marc Levine, MD Basic Science - Anticoagulation Medications B 2/4/2022 68 views 5.0 (1) Basic Science⎪Anticoagulation Medications Basic Science - Anticoagulation Medications Listen Now 23:11 min 10/21/2019 351 plays 5.0 (2)