Lecture 06 - Coagulation

Lecture 06 - Coagulation - Lecture 06 Coagulation Tests...

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Lecture 06 – Coagulation Tests Laboratory Tests - - Prothrombin Time (PT) o Not done as often as TT - Activated partial thromboplastin Time (aPTT) o Not done as often as TT - Thrombin Time (TT); [var. reptilase time] o Measures the last part of coagulation - Fibrinogen level o There is not enough of this molecule to form a thrombus then you will not achieve adequate hemostasis o The final molecule – if none then you don’t have normal clotting/coagulation - 1:1 mix with normal plasma: inhibitor screen o Also performed, take pt’s plasma & mix with normal plasma o The result will tell you if there is a factory deficiency or if there is an inhibitor - Individual factor assays, specific inhibitors o Done based on aPTT - Activated clotting time o Whole blood (don’t want to wait for lab so you can do it there and then in surgery room) - Urea clot solubility: FXIII activity o Measure the strength of meshwork by putting the clot in urea & measure F8 - Plasmin activity: dilute whole blood clot lysis time, euglobulin clot lysis o Fibrinolysis activity is measured by measuring plasmin acitivity - aPTT (activated prothrombin time) is triggered by o Negative charged surface in test tubes o Need to recalcify it in test tube since Ca+ + is needed for the rxn to occur Ca+ + = clotting o Purple top tube: has EDTA which binds Ca+ + and takes Ca+ + out fo the way to prevent clotting o Blue top tube: has citrate to make it unavailable for blood coagulation (by adding calcium you can start the rxn) o Measures the integreity of the intrinsic pathway with all its factor o Abnormal aPTT – abnormality to XII, XI, IX, X (12,11, 9,10) o Normal = 30 seconds - PT (Prothrombin Time) is the extrinsic o Measure TF that causes prothrombin --> thrombin o Abnormal PT – abnormality to VII (short half-life sensitive factor) Giving warfarin, liver disease o Normal = 10-12 seconds ***Clot is formed at end of coagulation cascade deficiencies of factors or inhibitors will increase aPTT and PT*** - 5M urea o Used to put clot into test to see how strong the fibrin cross-linked clot is o Not covalently linked fibrin polymer will result in the clot falling apart - DWBCLT o allow the blood to clot and check it at time intervals and if it falls apart in less than 4 hours plasmin activity excessive plasmin activity clot breaks down sooner o too much plasmin activity excessive fibrinolysis Thrombin Time / Reptilase Time - snake venom causes animal’s blood to clot quickly or to bleed excessively - prolonged TT: - prolonged RT:
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(measure of amount and quality of fibrinogen) Affected by: o low fibrinogen o dysfirbinogenemia o heparin Take citrate and anticoagulation plasma you see how long it takes for fibrin clot to form - fibrinogen is too low TT = longer - fibrinogen is abnormal (inherited or acquired, when liver can make dysfibrinogenemia) - excessive to HEPARIN (binds antithrombin in the plasma and that inhibits thrombin) (snake venom form fibrin clot Affected by: o low fibrinogen o dysfirbinogenemia o heparin insensitive
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