Week 2 - Hemostasis and Coagulation

Chapter 14: Alterations in Hemostasis and Blood Coagulation

• Hemostasis is the arrest of bleeding or the prevention of blood loss after blood vessel injury
• It involves the vessel wall, circulating platelets, and plasma coagulation proteins
• Learning Objectives include describing how platelets and clotting factors work in hemostasis, identifying findings from patient history and exams, laboratory tests, vascular alterations, causes of platelet deficiencies, excesses, and dysfunction, and inherited/acquired coagulation disorders

Evaluation of Hemostasis and Coagulation

• Patient history and physical exams are crucial to determine if & why a bleeding problem exists
• Personal and family history of bleeding disorders is key
• Active bleeding unresponsive to standard interventions needs evaluated
• Pre-surgical screening and ongoing anticoagulation therapy evaluation are part of the process
• Key aspects of clinical assessment include personal/family history of bleeding disorders, systemic diseases, medication history, and physical findings such as petechiae, purpura, ecchymosis, hematoma, hemarthrosis, telangiectasia, and occult or frank bleeding.

Laboratory Tests

• Primary and secondary hemostasis are evaluated
• Complete blood count (CBC) aids in anemia identification
• Platelet counts help determine platelet number
• Peripheral blood smears provide a visual assessment of platelet morphology
• Bleeding time evaluation considers vascular status and platelet function
• Prothrombin time (PT) and International Normalized Ratio (INR) evaluate the extrinsic pathway of coagulation
• Activated partial thromboplastin time (aPTT) assesses the intrinsic pathway

Bleeding Disorders

• Laboratory tests: specific lab values suggest various bleeding disorders, such as anemia, leukemia, disseminated intravascular coagulation (DIC), thrombocytopenia, platelet-vessel wall interactions, and deficiencies of coagulation factors (I, II, V, VII, VIII, IX, X)
• Vascular Purpura: Diagnosis is through exclusion, ruling out platelet and coagulation disorders. Tourniquet (Rumpel-Leede) test might be used. Treatment focuses on removing or avoiding the causative agent.
• Hereditary Hemorrhagic Telangiectasia (Osler-Weber-Rendu Disease): genetic trait, vessel wall composition, repeated bleeding episodes, and family history are significant factors. Supportive treatments, such as topical hemostatic agents, cauterization, iron replacement, and laser therapy, are key.

Platelet Disorders

• General Mechanisms of Thrombocytopenia: Involve decreased platelet production, survival, or splenic sequestration. This leads to low platelet count, prolonged bleeding time, and abnormal peripheral smears
• Treatment: Depends on the cause of thrombocytopenia
• Thombocytosis: Platelet count greater than 400.000/mm³. Can be transient (stress/physical activity) or primary (polycythemia vera, chronic granulocytic leukemia). Secondary to hemorrhage or disease. Treatment reserved for primary causes
• Qualitative Platelet Disorders: Platelet function problems; inherited (Bernard-Soulier syndrome, VonWillebrand's disease, thrombasthenia) or acquired (drug-induced, renal failure, hematologic disease). Treatment based on the underlying disorder; platelet transfusion may be needed

Coagulation Disorders

• Coagulopathies: Defects within the normal clotting mechanism.
• Results: Bleeding from problems in clot formation, stabilization or lysis of the fibrin clot, or excessive clot formation.
• Hemophilia: Hereditary coagulation disorder, most common resulting in excessive bleeding. Hemophilia A (factor VIII deficiency), Hemophilia B (factor IX deficiency). Treatment includes patient/family education; cryoprecipitate or factor VIII concentrate (Hemophilia A), fresh frozen plasma or cryoprecipitate (Hemophilia B).
• Von Willebrand Disease: Autosomal dominant disorder of factor VIII carrier protein leading to platelet dysfunction and excessive bleeding, Treatment with desmopressin (to release von Willebrand factor and factor VII from endothelial cells); cryoprecipitate and humate-P for severe bleeding.
• Vitamin K Deficiency Bleeding in Infancy: Lack of vitamin K-dependent coagulation factors (II, VII, IX, X), early bleeding (melena, hematuria, intracranial hemorrhage, hypovolemic shock). Prophylactic vitamin K to the newborn prevents this.
• Acquired Vitamin K Deficiency: Can occur from malnutrition, malabsorption, chronic hepatic disease, antibiotic therapy, or oral anticoagulation; results in excessive bleeding. Treatment with parenteral vitamin K
• Disseminated Intravascular Coagulation (DIC): Acquired hemorrhagic syndrome where clotting and bleeding happen simultaneously. Fibrinogen and platelet counts are reduced. Increased bleeding time, elevated PT/INR/aPTT/D-dimer. Treatment focuses on the cause

Hepatic Disease

• Coagulopathies emerge from Impaired vitamin K absorption, decreased synthesis of fibrinogen/factors V and XI, trouble removing activated coagulation factors and fibrinolytic proteins, and problems with coagulation inhibitor production.
• Treatment consists of vitamin K, platelet transfusions, fresh frozen plasma, or whole blood.