Haemostasis
Haemostasis The function of haemostasis is: to prevent blood loss from injured vessels to stop bleeding to prevent thrombosis
Haemostasis blood endothelium basement membrane subendothelium normal vessel wall The normal intact endothelium is non thrombogenic and neither reacts with platelets nor coagulation factors
Haemostasis platelets factors blood endothelium basement membrane subendothelium vessel wall damage When a vessel wall is damaged, there may be endothelial loss and exposure of the subendothelium to platelets and coagulation factors
Haemostasis It is convenient to divide haemostasis into : primary haemostasis coagulation fibrinolysis
Primary haemostasis
artist's view Primary Haemostasis inert platelet platelet adhesion shape change release aggregation coagulation fibrin
artist's view Platelets Adhesion glycoprotein receptor Gp Ib vwf subendothelial collagen platelet VIII:C von Willebrand factor
artist's view Platelets Aggregation GP IIb/IIIa fibrinogen GP IIb/IIIa Platelet
artist's view Platelets Aggregation endothelium Sous endothelium
Coagulation
Coagulation Fibrin, the final product of the blood coagulation, consolidates the platelet plug
Coagulation factors Usual name Factor Function Fibrinogen I Substrate Prothrombin II Zymogen Proaccelerin V Cofactor Proconvertin VII Zymogen Anti-hemophilic factor A VIII Cofactor Anti-hemophilic factor B IX Zymogen Stuart factor X Zymogen Rosenthal factor XI Zymogen Hageman factor XII Zymogen Fibrin stabilising factor XIII Zymogen
Vitamin K-dependant factors Coagulation factor CH2 COO - Ca ++ Coagulation factors II, VII, IX, X require a carboxyl group platelet phospholipids* * Platelet factor 3
Coagulation Cascade Activation Extrinsic pathway Intrinsic pathway Common Pathway Formation of thrombin Formation of fibrin Clot
Intrinsic Pathway H M W K XII axii XI axiia bxiia XIa PKK KK contact HMWK: high molecular weight kininogen PKK: prekallicrein KK: kallicrein PF3: platelet factor 3 Ca++ Ca++ IX PF3 IXa + VIII PF3
Extrinsic Pathway VII VIIa Thromboplastin Ca++ X Xa + V PF3: Platelet Factor 3 PF3 PF3
Fibrin formation Prothrombin II Thrombin IIa + 2 fibrinopeptides A + 2 fibrinopeptides B Fibrinogen factor I Fibrin monomer Fibrin monomer fibrin fibrin fibrin fibrin fibrin fibrin fibrin fibrin soluble fibrin polymer
Clot formation Prothrombin II Thrombin IIa XIII XIIIa XIII XIIIa fibrin fibrin fibrin fibrin fibrin fibrin fibrin fibrin cross-linked fibrin
Clot fibrin fibrin fibrin fibrin fibrin fibrin fibrin fibrin fibrin fibrin fibrin fibrin fibrin fibrin fibrin fibrin stabilised cross-linked fibrin fibrin fibrin fibrin fibrin fibrin fibrin fibrin fibrin
Fibrinolysis fibrinolysis dissolves the clot protects from thrombosis
Fibrinolysis enzymes (tpa, upa) plasminogen plasmin tpa: tissue Plasminogen Activator upa: urokinase Plasminogen Activator Clot Degradation products
Fibrinolysis plasmin plasmin plasmin plasmin From Moseson MW, J Lab Clin Med, 1990
Fibrin Degradation Products E D-DIMER Fragments containing D-DIMER From Moseson MW, J Lab Clin Med, 1990
D-DIMERS fibrin degradation products - can be produced only after fibrin formation and cross-linking (factor XIII) test (with monoclonal antibodies) detects breakdown products of plasmin action on fibrin clot Reference value: highly depends on sensitivity of method <200 ng/ml (in our lab)
Fibrinogen Degradation Products (FDP) Fibrinogen FDP-X FDP-Y FDP-D FDP-D FDP-E
Hemostasis system as a balance factors phospholipids Ca ++ tpa upa + clotting thrombin _ FIBRIN + fibrinolysis plasmin _ AT III protein C protein S PAI-1 antiplasmin
artist's view Defects in haemostasis bleeding disorder
artist's view Defects in haemostasis thrombosis
Tests for vascular disorders bleeding time functional tests specialistic tests eg biopsy of the skin
Tests for platelets disorders bleeding time platelets count blood smear platelets functional tests adhesion of platelets aggregation release reaction from platelets granules flow cytometry tests
Tests for plasma coagulation disorders recalcification time aptt activated partial thromboplastin time PT prothrombin time TT - thrombin time fibrinogen concentration o particular plasma coagulation factors o circulating anticoagulants o inhibitors of coagulation
Tests for fibrinolytic disorders euglobulin lysis time thrombin time FDP plasminogen inhibitors of coagulation activators of coagulation
Regulation of blood coagulation antithrombin III protein C protein S
Sample collection PLATELETS EDTA or citrate NEVER!!! use heparine
Platelets count 150000 450000/mm3
Thrombocytosis > 400000 1000000/ul malignancy myeloproliferative diseases polycythaemia vera chronic myelogenous leukaemia essential thrombocytosis after surgery splenectomy! collagen disorders rheumatoid arthritis acute infection iron deficiency anaemia haemolytic anaemia cryoglobulinemia malaria parasites pseudothrombocytosis liver diseases chronic pancreatitis
Thrombocytopenia < 150000/ul idiopathic thrombocytopenic purpura (ITP) haematologic disorders: leukaemia, lymphoma, metastatic carcinoma, anemias (aplsatic, vitb 12, folic acid deficiency) hypersplenism thrombotic thrombocytopenic purpura DIC post transfusion and massive blood transfusions hereditary thrombocytopenic purpura infections (AIDS, subacute bacterial endocardtitis, septicaemia) other diseases (SLE) bone marrow suppressive agents (antitumour drugs, radiati on) drug sensitivity reactions (sulfonamides, chloramphenicol)
Reference values BLEEDING TIME (I) (Duke s method) < 5 min (Ivy technique) 2-9 minutes only test which informs about primary haemostasis best screening test for platelet abnormalities (number and function) test for microvascular function normal test without suggestive history usually excludes platelet dysfunction
BLEEDING TIME (II) Prolonged in: thrombocytopenia (correlation between severity of thrombocytopenia and degree of bleeding time prolongation when platelets are less then 100000/ l) defects of platelet function: hereditary (eg von Willebrand Disease, Glanzmann's thrombastenia, Wiskott-Aldrich syndrome) acquired drugs aspirin, nonsteroidal anti-inflammatory drugs vessles disorders
PLASMA COAGULATION DEFECTS
Sample collection sodium citrate thin needle without syringe without tourniquet
Sample collection Routine venipuncture use 2 syringe draw (first may be contaminated by tissue thromboplastine) avoid limb used for heparin therapy avoid excessive manipulation of vein avoid overly tight or prolonged tourniquet
PROTHROMBIN TIME - PT (I) Clotting time after addition to anticoagulated plasma complete tromboplastin = substitute for tissue factor and Ca 2+ extrinsic and common pathways 12-16 s
PROTHROMBIN TIME - PT (II) Clinical use screening the abnormality of extrinsic and common pathway (VII, V, X, II, fibrinogen) monitoring long-term anticoagulant therapy evaluation of liver function (protein synthesis - prothrombin complex factors (factors II, VII, X, proteins C and S)
PROTHROMBIN TIME - PT (III) Should be reported as INR (International Normalized Ratio) INR = (patient PT / mean PT) ISI ISI=International Sensitivity Index provided by thromboplastin manufacturer Reference value 0,9 1,25 Prolonged in: defect in factors: I (fibrinogen), II ( prothrombin), V, VII, X severe liver damage defect in factors VII, V, X, II (assays <30% of normal), fibrinogen (<1g/l) inadequate vitamin K in diet (vit K dficincy) liver disease (eg poisoning, hepatitis, alcoholism) anticoagulant therapy very sensitive to foctor VII and X deficiency
ACTIVATED PARTIAL THROMBOPLASTIN TIME aptt Reference value: depends on lab and on reagents 25 45 sec examines the integrity of intrinsic system and the common pathway
ACTIVATED PARTIAL THROMBOPLASTIN TIME aptt measures the clotting time of anticoagulated plasma after addition of "partial thromboplastin" ( a phospholipid emulsion equivalent to platelet phospholipid) Ca++, kaolin phospholipid Used in screening the abnormality of intrinsic and also common pathway (XII, XI, IX, VIII, V, X, II, fibrinogen), especially haemophilia A and B monitoring heparin therapy detecting clotting inhibitors
ACTIVATED PARTIAL THROMBOPLASTIN TIME aptt Prolonged in: defect in factors: I, II, V, VII, IX, X, XI, XII presence of specific inhibitors of clotting factors (most often antibodies against factors in multitransfused patients) defect in factors XII, XI, IX-haemophilia B,VIIIhaemophilia A, V, X, II (assays <30% of normal), fibrinogen presence of specific inhibitors of clotting factors, eg antibody against factor VIII, lupus anticoagulant presence of fibrin degradation products normal in: thrombocytopenia platelet dysfunction
THROMBIN TIME Reference value: depends on lab and on reagents 16 20 sec examines the final step in the common pathway (leading to the formation of noncross-linked fibrin from fibrinogen) measures the clotting time of anticoagulated plasma after addition of exogenous thrombin and Ca++
THROMBIN TIME Clinical use: detecting abnormalities in fibrinogen: concentration function and structure detecting interference with polymerisation of fibrin: fibrin degradation products
THROMBIN TIME Prolonged in: very low (<0,8g/l) or very high (>4g/l) level of fibrinogen dysfibrinogenemia presence of fibrin degradation products paraproteinemia (eg monoclonal immunoglobulins) uraemia specimen contamination with heparin
A EUGLOBULIN LYSIS TIME measures fibrynolytic activity in plasma euglobulin fraction = all plasma coagulation factors and activators of fibrynolysis (relatively free from inhibitors of fibrinolysis) anitcoagulated plasma is precipitated in cold by adding acetic acid, in this precipitate is only fraction of euglobulin, then the precipitate is dissolved and clotted with thrombin and Ca 2+, time of dissolving the clot is measured Reference value: 120 240 min
A EUGLOBULIN LYSIS TIME Shortened in: - increased plasmin activity - increased plasma plasminogen activator activity (eg in advanced liver disease) - reduced plasma fibrinogen concentration
Screening tests for presumptive diagnosis of common bleeding disorders Platelet Count B P T APT T T LOCATION OF DEFECT MOST FREQUENT CAUSES ACQUIRED N N I N extrinsic pathway -liver disease -coumarin therapy -vit k deficiency -DIC (very rare) HEREDITARY - deficiency of factor VII (very rare) N N N I intrinsic pathway - heparin therapy -hemophilia A or B -deficiency of factor XI -deficiency of factor XII -deficiency of prekallikrein -deficiency of high-molecular weight kininogen -deficiency of Passavoy factor N* N I I common or multiple pathways -heparin therapy -liver disease, vit K deficiency -DIC -fibrigenolysis (very common) -deficiency of factor V -deficiency of factor X -dysfibrinogenemias (very rare) D I N N Thrombocytopenia -ITP -drugs -Aldrich's syndrome N or I I N N disorder of platelet function -thrombocytopenia -drugs -thrombasthenia -deficient release reaction
DIC panel D-Dimer Platelet Count Fibrinogen PT aptt