Why is my Patient Bleeding? A Snapshot of Hemostasis
To view source article and take the Quiz- click on image above 🙂
Editor’s Note:
Having just finished a case where we used Angiomax as our heparin substitute, I felt that the anticoagulation pathway, is truly a complex animal, and deserves a closer review.
We have all revisted this pathway intensively throughout our careers, and of course, we have all been clinically challenged by open-heart cases that test our fundamental understanding of coagulation theory in real time, at a level that certainly reflects a fairly deep dive into esoteric hematology.
So i am keeping it simple, and found information from two sites, that in my opinion transforms the complex picture of a picture like this, by MC Escher…
Into something a little more clinically palatable such as this Salvador Dali Painting…
I hope I haven’t offended any art critics out there 🙂
Part 2 comes out tomorrow.
Preview Flashcards
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Front Back
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What is Factor I and what pathway?
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Fibrinogen, Final Common Pathway
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What is Factor II and IIa and? what pathway
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Prothrombin and Thrombin, Final Common pathway
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What is Factor III and what pathway?
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Thromboplastin, Extrinsic Pathway
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What is Factor IV and what pathway?
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Calcium, Extrinsic Pathway
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What is Factor V and what pathway?
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Proaccelerin, Final Common Pathway
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What is Factor VI and what pathway?
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Trick Question, there is no factor VI
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What is Factor VII and what pathway?
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Proconvertin, Extrinsic Pathway
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What is Factor VIII and what pathway?
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VIII c is antihemophilic factor, VIIIvWF is Von Willenbrand’s pathway. It is part of the Intrinsic Pathway
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What is Factor IX and what pathway?
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Christmas Factor, Intrinsic Pathway
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What is Factor X and what pathway?
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Stuart Power Factor, Final Common pathway
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What is Factor XI and what pathway?
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Plasma Thromboplastin Antecedent, Intrinsic pathway.
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What is Factor XII and what pathway?
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Hageman Factor, intrinsic Pathway
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What is Factor XIII and what pathway?
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Fibrin Stabilizing Factor, Final Common Pathway.
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Which Factors are K dependent?
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2, 7, 9, 10
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What assesses Heparinization? What are the normal values? What value do you want with adequate anticoagulation?
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PTT, ACT. Normal is PTT 24-35, ACT 80-150. For adequate anticoagulation you want ACT 400-450.
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What assesses Coumadin and what are the normal values?
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PT and INR. Normal is PT 12-14 seconds, and INR is normally 1.
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What pathway does Heparin affect?
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Interferes with the Intrinsic and final common pathway.
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What is normal Platelet count. What is the minimum to get an epidural.
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normal is 150-400,000. minimum for epidural is 100,000
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What is normal bleeding time?
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3-10 minutes
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What is normal Thrombin Time and what does it assess?
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Normal Thrombin Time is 12-20 seconds. It assesses the final common pathway.
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What pathway does Coumadin affect?
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It affects the Extrinsic and Final Common Pathway.
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How does Heparin work?
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It enhances antithrombin III.
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Why do we transfuse RBCs
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To increase the oxygen carrying capacity of the blood.
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What is the average lifespan of a platelet?
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8-12 days
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What is involved in platelet adhesion?
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vWF (factor 8), it is made in the endothelial cells and attaches platelets to damaged endothelium
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what is the most common inherited coagulation defect?
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vWF defect
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What are the treatments in order for vWF defect?
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1st DDAVP – relies on endogenous vWF. 2nd Cryoprecipitate – contains VIII and I. 3rd factor VIII concentrate
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What happens in platelet activation?
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Thrombin (factor 2a) attaches to its receptor and causes platelets to change shape and release thromboxane A2 and ADP.
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What happens in platelet aggregation?
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Thromboxane A2 and ADP uncover fibrinogen receptors which bind fibrinogen (factor 1) and link platelets together.
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How do Aspirin and NSAIDS interfere with clot formation?
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They interfere with platelet aggregation by blocking the COX pathway so Thromboxane A2 isn’t produced. Aspirin is 8-12 days, NSAIDS last 24-48 hrs
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What is the most common acquired platelet disorder?
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Aspirin or NSAIDS
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How is Fibrin Produced?
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After platelet aggregation, Thrombin (IIa) produces Fibrin at the site of injury, crosslinks platelets requiring factor XIII.
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How do we remember the Extrinsic pathway, and what triggers it?
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4 37 cents you can buy the extrinsic pathway. Thromboplastin and factor VII. Initiated w/ damage to the outside of the blood vessel.
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How do we remember the intrinsic pathway and what triggers it?
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It is initiated w/ damage to the inside of the vessel.
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How do we remember the final common pathway?
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What reverses Heparin?
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Protamine
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What is the primary physiologic initiator of coagulation?
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Thromboplastin (factor III)
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Where is thromboplastin synthesized.
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Synthesized in endothelial cells.
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Hemophilia A – what is it and what is treatment?
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Factor VIII:c deficency. Txt with FFP and Cryoprecipitate 1st or with pooled VIII concentrate.
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Hemophilia B – what is it and what is the treatment?
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It is a deficiency of factor IX (christmas factor). Txt is with factor IX concentrate.
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What is the best measurement of platelet function and what are the normal values?
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Bleeding time, normally 3-10 minutes
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What causes DIC? What are the signs and symptoms?
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Sepsis, shock, ischemia. Bleeding from surgical sites, all clotting factors down, platelets down, end fibrin split products elevated.
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What does FFP Contain?
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All pro-coagulants except platelets. Still need to be activated by the liver.
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What does cryoprecipitate contain?
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Factor VIII (vWF), I (fibrinogen), and XIII (fibrin stabilizing factor.
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What is antithrombin III and how does it work?
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Made in liver, neutralizes Thrombin (IIa) and X, IX, XI, and XII. Binds Thrombin and X most. Enhanced by heparin 1000x
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Why would a patient not respond to Heparin?
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Lack of Antithrombin III. Heparin requires antithrombin III in order to enhance its action. Txt w/ FFP as long as you have a working liver.
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What does Plasmin do?
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It breaks down fibrin, made as plasminogen in the liver.
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How is plasminogen activated?
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TPA and UPA convert plasminogen to plasmin, which binds fibrin within a clot and dissolves it.
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What is TPA?
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Has high affinity to fibrin. Converts plasminogen to plasmin. Is made by endothelial cells. Is stimulated by thrombin and venous stasis.
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what is UPA and Streptokinase?
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Both have less affinity for fibrin, UPA is found in limited quantities in the blood. Streptokinase is produced by B hemolytic step.
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What is Aprotinin
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antifibrinolytic agent, inhibits plasmin, slows fibrin breakdown by preventing plasmin binding. used to prevent bleeds in cardiac surgery
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What is Amicar
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prevents fibrin breakdown by preventing plasmin from attaching to fibrin. Controls hemorrhage w/ fibrinolysis from too much plasminogen activation.
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What factors are produced by endothelial cells?
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vWF (VIII), TPA, Thromboplastin (III)
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What is the order of platelet function?
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Adhesion (vWF), Activation (Thrombin), Aggregation (Thromboxane A2 and ADP), Fibrin Production (Thrombin and Intrinsic, Extrinsic, and Final Common Pathways)
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