Hemostasis Physiologic mechanisms to protect from blood loss. Stops bleeding from an injured site Maintains blood in the fluid state within the vascular compartment HEMORRHAGE THROMBOSIS
Normal Hemostatic Mechanisms VASCULAR SYSTEM PLATELETS COAGULATION SYSTEM Intrinsic Pathway VIII, vWF, IX, XI, XII, prekallikrein, HMWK Extrinsic Pathway III, VII Common Pathway FIBRINOLYTIC SYSTEM
Primary Phase – formation of platelet plugs Secondary Phase – formation of fibrin plugs
Bleeding Disorders SPONTANEOUS - petechiae, purpura, mucous membranes, GI bleeding, hematuria, into joint spaces EXCESSIVE - after trauma or surgery - range is from lethal diseases (factor VIII deficiency, Bernard-Soulier's, Glanzmann's) to asymptomatic (factor XII deficiency, many von Willebrand's)
PLATELETS DEFICIENCY or DYSFUNCTION apparent immediately after trauma (petechiae – skin & mucus membranes) Thrombocytopenia count is less than 100 x 109/liter bleeding after trauma = platelet count is below 40 x 109/liter spontaneous bleeding = count is below 20 x 109/liter (petechiae &purpura randomly over the skin, blood blisters in the mouth, GI, GU, CNS bleeding.) severe spontaneous bleeding = when count gets < 10 x 109/liter
DERANGEMENTS OF CLOTTING FACTORS apparent only few minutes after trauma deficiency can be mild or severe absent or defective or the deficiency may be due to an inhibitor against it hereditary (single) or acquired (several) ecchymoses or hematomas after minor injury, bleeding for days after tooth extractions, or bleeding into joint spaces (hemarthroses)
Hemophilia Hemophilia A – deficient Factor VIII Sex-linked levels less than 1% of normal Hemophilia B – deficient Factor IX (Christmas disease) Sex-linked Assay of corresponding factor/s
Von Willebrand’s Disease Autosomal dominant Type I – most common, inhibited release of multimers by unknown mechanisms, less amount is available Type II – defective multimers are released Type III – none is produced Usually associated with reduced Factor VIII
FIBRINOLYTIC Problems Excessive plasminogen activation Elevated fibrin degradation products DISSEMINATED INTRAVASCULAR COAGULATION Thrombohemorrhagic disorder SECONDARY COMPLICATION activation of coagulation sequence microthrombi formation with consumption of platelets, fibrin & coagulation factors activation of fibrinolytic mechanisms
DISSEMINATED INTRAVASCULAR COAGULATION signs and symptoms relating to infarction hemorrhagic diathesis due to depletion of platelets and clotting factors AND activation of fibrinolytic mechanisms Mechanisms: release of tissue factor and thromboplastic substances into the circulation endothelial injury
HYPERCOAGULABLE BLOOD – Thrombosis "Thrombophilia“, "hypercoagulopathy“ Not rare, but tends to get overlooked. deficient natural anticoagulants (Protein C, Protein S and Antithrombin III) Sticky platelet syndrome Dysfibrinogenemia - mutant fibrin is not removed by plasmin plasminogen deficiency
Laboratory Screening Tests Primary Phase – Bleeding Time Secondary Phase – Clotting Time
Laboratory Screening Tests VASCULAR SYSTEM – capillary fragility testing (tourniquet test) PLATELETS – count and function (CRT) COAGULATION SYSTEM Intrinsic Pathway – APTT Extrinsic Pathway – Prothrombin time Common Pathway – Thrombin time FIBRINOLYTIC SYSTEM – FDP, antithrombin, natural anticoagulants
Laboratory Tests – SPECIFIC Platelet Function Tests Assays of Clotting Factors and Anticoagulants Detections of antibodies against coagulation elements
SUMMARY Tourniquet Tests – (+) or (-) Bleeding Time – (N) or (P) Clotting Time – (N) or (P) Platelet Count – (N) or Dec or Inc Clot Retraction Time – (N) or Abn Prothrombin Time – (N) or (P) Activated Partial Thromboplastin Time – (N) or (P) Thrombin Time – (N) or (P) What Specific Tests?
COAGULATION DISORDERS by: Noel C. Santos, M.D.