Week 6: Secondary Hemostasis Plasmatic factors Plasmatic factors Intrinsic pathway Intrinsic pathway...
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Transcript of Week 6: Secondary Hemostasis Plasmatic factors Plasmatic factors Intrinsic pathway Intrinsic pathway...
Week 6: Secondary Hemostasis
Plasmatic factorsPlasmatic factors Intrinsic pathwayIntrinsic pathway Extrinsic pathwayExtrinsic pathway SpecimenSpecimen PPP preparationPPP preparation PT, INRPT, INR APTTAPTT TTTT Vitamin KVitamin K Liver diseaseLiver disease
Factor deficiencyFactor deficiency Circulating inhibitorsCirculating inhibitors HeparinHeparin CoumarinCoumarin Lupus inhibitorLupus inhibitor Factor assayFactor assay Mixing and substitution Mixing and substitution
studiesstudies 5M urea test5M urea test Lee-White clotting timeLee-White clotting time
Plasmatic Factors
Intrinsic pathway activated by contact to Intrinsic pathway activated by contact to collagen: HMWK, prekallikrein, XII, XI, collagen: HMWK, prekallikrein, XII, XI, IX, VIIIIX, VIII
Extrinsic pathway activated by tissue Extrinsic pathway activated by tissue thromboplastin: VIIthromboplastin: VII
Common pathway: X, V, II, ICommon pathway: X, V, II, I
RBC’s trapped in fibrin strands SEM x 6,400
Fibrin Formation
D and E domains on fibrinogenD and E domains on fibrinogen Thrombin cleaves fibrinopeptidesThrombin cleaves fibrinopeptides Spontaneous polymerization (unstable)Spontaneous polymerization (unstable) Disulfide cross-linkages between D Disulfide cross-linkages between D
domains by the action of XIIIdomains by the action of XIII
Inhibitors
Anti-thrombin III with heparin: II, IX, X, Anti-thrombin III with heparin: II, IX, X, XI, XIIXI, XII
Protein C and protein S: slow down VIII Protein C and protein S: slow down VIII and Vand V
Heparin: quick acting but short lived and Heparin: quick acting but short lived and need AT-IIIneed AT-III
Coumarin: vitamin K antagonistCoumarin: vitamin K antagonist
Vitamin K Dependent Factors
Caboxylation to chelate CaCaboxylation to chelate Ca++++
II, VII, IX, X, protein C, protein SII, VII, IX, X, protein C, protein S Liver synthesis inhibited by coumarinLiver synthesis inhibited by coumarin
Specimen
Clean phlebotomy requiredClean phlebotomy required 3.2% vs 3.8% citrate3.2% vs 3.8% citrate 1:9 citrate to blood ratio1:9 citrate to blood ratio Transport to lab quickly and separate Transport to lab quickly and separate
plasmaplasma Platelet poor plasma (PPP)Platelet poor plasma (PPP) Test without delay or store frozenTest without delay or store frozen
Instrumentation
Electro-mechanical (e.g., Fibrometer)Electro-mechanical (e.g., Fibrometer) Physical detection of clotPhysical detection of clot Cannot be automatedCannot be automated
Optical (e.g., MLA, ACL)Optical (e.g., MLA, ACL) Interference with icteria or lipemiaInterference with icteria or lipemia Can be automatedCan be automated
Basic Hemostasis Tests
Plasmatic factorsPlasmatic factors Thrombin timeThrombin time Prothrombin timeProthrombin time Activated Partial Activated Partial
Thromoplastin timeThromoplastin time 5M urea test (factor 5M urea test (factor
XIII)XIII) PlateletPlatelet
Platelet countPlatelet count Platelet function testPlatelet function test
Vascular integrityVascular integrity Bleeding timeBleeding time Tourniquet testTourniquet test
OthersOthers FDP, D-dimerFDP, D-dimer Factor assaysFactor assays Anti-thrombin IIIAnti-thrombin III Proteins C and SProteins C and S Factor V LeidenFactor V Leiden
Activated Partial Thromboplastin Time (APTT) For intrinsic pathway factorsFor intrinsic pathway factors Lee-White clotting timeLee-White clotting time
Whole blood at 37Whole blood at 37ooCC Glass test tube for surfaceGlass test tube for surface
Phospholipid platelet substitutePhospholipid platelet substitute Activator: kaolinActivator: kaolin 0.02M CaCl0.02M CaCl22
Monitor heparin therapyMonitor heparin therapy
Prothrombin Time (PT)
For extrinsic pathway factorsFor extrinsic pathway factors Tissue thromboplastin (rabbit brain) with Tissue thromboplastin (rabbit brain) with
CaCa++++
European labs use Tpl from human source, European labs use Tpl from human source, so more sensitiveso more sensitive
INR = (Pt PT/normal PT)INR = (Pt PT/normal PT)ISIISI
Monitor coumarin therapyMonitor coumarin therapy
Thrombin Time (TT)
Fibrinogen screenFibrinogen screen Thrombin reagentThrombin reagent Clotting time corresponds to fibrinogen Clotting time corresponds to fibrinogen
levellevel
Other Tests
Factor assay: reconstitute patient plasma Factor assay: reconstitute patient plasma with known deficient plasma and determine with known deficient plasma and determine clotting timeclotting time
FDP and D-dimer tests for fibrinolysisFDP and D-dimer tests for fibrinolysis Fibrinogen assay: modified TTFibrinogen assay: modified TT 5M urea test for factor XIII5M urea test for factor XIII Plasma protamine-sulfate paracoagulation Plasma protamine-sulfate paracoagulation
test (3P) for fibrin monomerstest (3P) for fibrin monomers
Mixing and Substitution Tests
1:1 with normal plasma: screen for 1:1 with normal plasma: screen for circulating inhibitorcirculating inhibitor
Aged serum has: II, VII, IX, XI, XIIAged serum has: II, VII, IX, XI, XII Barium sulfate adsorbed plasma has: I, V, Barium sulfate adsorbed plasma has: I, V,
VIII, XI, XIIVIII, XI, XII
Abnormal Coagulation Tests
Check specimen collectionCheck specimen collection Phlebotomy, anticoagulantPhlebotomy, anticoagulant Patient conditionPatient condition MedicationMedication
Check specimen integrityCheck specimen integrity Storage temperatureStorage temperature PPP preparationPPP preparation
Check reagent integrityCheck reagent integrity Check instrument QCCheck instrument QC
Abnormal APTT
Hemophilia A (VIII) if maleHemophilia A (VIII) if male Christmas disease (IX) if maleChristmas disease (IX) if male Liver disease: multi-factor deficiencyLiver disease: multi-factor deficiency HypofibrinogenemiaHypofibrinogenemia HeparinHeparin Anti-phospholipid antibody (Lupus inhibitor): do Anti-phospholipid antibody (Lupus inhibitor): do
a 1:1 mix with normal plasmaa 1:1 mix with normal plasma Von Willebrand’s: variableVon Willebrand’s: variable
Abnormal PT
Coumarin therapyCoumarin therapy Vitamin K deficiency, especially in Vitamin K deficiency, especially in
newbornnewborn More sensitive to common pathway factors More sensitive to common pathway factors
than APTTthan APTT HeparinHeparin
Abnormal TT
DysfibrinogenemiaDysfibrinogenemia AfibrinogenemiaAfibrinogenemia HypofibrinogenemiaHypofibrinogenemia HeparinHeparin FDP: forms abnormal complexFDP: forms abnormal complex
Hyper-coagulable State
Deep vein thrombosis due to inappropriate Deep vein thrombosis due to inappropriate coagulationcoagulation
Protein C and protein S deficiencyProtein C and protein S deficiency Anti-thrombin III deficiencyAnti-thrombin III deficiency Factor V Leiden mutation: does not Factor V Leiden mutation: does not
respond to protein C (activated protein C respond to protein C (activated protein C resistance, APCR)resistance, APCR)