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Unformatted text preview: 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 ( activa t e d prothro mbin ti m e ) 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 Nor m al = 3 0 seconds- PT (Pro thro mbin Tim e) 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 Nor m al = 1 0-1 2 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: (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...
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This note was uploaded on 09/14/2011 for the course PHARM HEM taught by Professor Staff during the Spring '11 term at UCSD.
- Spring '11