Primary Hemostasis Quiz

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Questions and Answers

What is the first step in primary hemostasis?

Release of granules

Platelet aggregation

Platelet adhesion (correct)

Platelet activation

Which factor is primarily responsible for platelet adherence to collagen?

Von Willebrand Factor (vWF) (correct)

Platelet factor 4

Thrombin

Fibrinogen

What occurs after platelet adhesion and shape change during primary hemostasis?

Coagulation cascade activation

Release of granules (correct)

Fibrinolysis

Vascular constriction

In the coagulation cascade, which component is involved in the aggregation of platelets?

Fibrinogen Signup and view all the answers

Which of the following describes a common disease associated with primary hemostasis?

von Willebrand Disease Signup and view all the answers

What is the purpose of laboratory tests evaluating hemostasis?

To evaluate the efficiency of the coagulation cascade Signup and view all the answers

Which step follows platelet activation during primary hemostasis?

Aggregation Signup and view all the answers

What triggers the initiation of primary hemostasis?

Endothelial injury Signup and view all the answers

What is the primary role of von Willebrand Factor (vWF) in platelet function?

It facilitates adhesion of platelets to exposed collagen. Signup and view all the answers

Which step follows platelet adhesion in primary hemostasis?

Platelet shape change Signup and view all the answers

What is formed as a result of fibrinogen bridging adjacent activated platelets?

A hemostatic plug Signup and view all the answers

Which of the following is a quantitative method used to assess primary hemostasis?

Thrombogram Signup and view all the answers

Which of the following tests assesses the qualitative function of platelets?

Buccal Mucosal Bleeding Time (BMBT) Signup and view all the answers

What triggers the activation of platelets during primary hemostasis?

Exposure of subendothelial collagen Signup and view all the answers

What characterizes the aggregation of platelets in primary hemostasis?

It is reversible and mediated by fibrinogen. Signup and view all the answers

In which condition would platelet abnormalities most likely be observed?

All of the above Signup and view all the answers

What may suggest accelerated thrombopoiesis in a clinical setting?

Increased mean platelet volume (MPV) Signup and view all the answers

Which is NOT a cause of decreased platelet production?

Immune-mediated thrombocytopenia Signup and view all the answers

Which condition is associated with increased utilization of platelets?

Vasculitis Signup and view all the answers

What is the most common inherited hemostatic disorder in dogs?

Von Willebrand Disease Signup and view all the answers

Which option describes a transient thrombocytosis after splenectomy?

Redistribution of platelets Signup and view all the answers

What is a common cause of reactive thrombocytosis?

Inflammation with cytokine release Signup and view all the answers

What does the presence of immune-mediated thrombocytopenia indicate?

Destruction of platelets Signup and view all the answers

What aspect of platelet function may be affected by congenital disorders?

Platelet aggregation Signup and view all the answers

What characterizes Type 2 Von Willebrand Disease?

Qualitative defects in vWF Signup and view all the answers

Which condition is associated with severe, acute blood loss leading to increased platelet consumption?

Disseminated intravascular coagulation (DIC) Signup and view all the answers

Study Notes

Coagulation: Review of Diseases of Primary and Secondary Hemostasis

This presentation covers coagulation, diseases of primary and secondary hemostasis
Learning objectives include defining key components of hemostasis, identifying anticoagulants for lab tests, understanding primary and secondary hemostasis tests, common hemostatic diseases, and using lab data to diagnose issues in the coagulation cascade.

Lecture Outline

The lecture will review primary and secondary hemostasis, followed by a laboratory evaluation of common diseases

Primary Hemostasis: Steps

Endothelial injury exposes subendothelial collagen.
Platelets adhere to exposed collagen via von Willebrand Factor (vWF).
Adhesion causes platelet activation, altering shape and releasing granules.
Fibrinogen bridges adjacent activated platelets, leading to aggregation (reversible).
A primary hemostatic plug forms.

Primary Hemostasis: Tests

Quantitative: platelet number (platelet count, blood smear), thrombogram (automated platelet count).
Qualitative: platelet function (Buccal Mucosal Bleeding Time [BMBT]), von Willebrand Factor (vWF) antigen assay.

Primary Hemostasis Disorders

Platelet abnormalities involve morphology and function.
Abnormal Morphology: Includes giant platelets (larger than RBCs), suggesting accelerated thrombopoiesis (platelet regeneration), potentially seen with macrothrombocytopenia (CKCS), and generally increased mean platelet volume (MPV).
Thrombocytopenia: Four main causes (S.P.U.D.):
- Sequestration (trapping in spleen, splenomegaly, splenic congestion/neoplasia)
- Production (decrease in bone marrow function, aplastic anemia, toxins, drugs, infections, etc.)
- Utilization (increased consumption from DIC, vasculitis, endocarditis, severe hemorrhage).
- Destruction (immune-mediated thrombocytopenia [ITP], primary/secondary)
Thrombocytosis (increased platelet count): Two types
- Primary: Very rare, associated with a persistent, extreme thrombocytosis (> 1 million platelets/µL). Possible causes include essential thrombocythemia (ET), acute megakaryoblastic leukemia (AML-M7). Often increases risk of thrombosis and hemorrhage.
- Secondary (Reactive): Several causes include increased production (inflammation, recovery from thrombocytopenia, chemotherapy, iron deficiency), redistribution (stress response, exercise), decreased removal (splenectomy), excess cortisol.

Abnormal Platelet Function

Platelet count is usually normal or elevated, caused by inherited or acquired disorders.
Dysfunction can be linked to adherence, aggregation, surface membrane receptors, or product synthesis/release.

Von Willebrand Disease (vWD)

vWD is the most common inherited hemostatic disorder in dogs (e.g. dobermans, scotties, shelties).
It involves a deficiency or abnormality of von Willebrand Factor (vWF).
It has three main types (1, 2, and 3) differentiating by the type of issue with vWF. Type 1 is most common, characterized by a reduced amount of functional vWF.
Clinical signs often involve prolonged bleeding from wounds, mucous membrane hemorrhage (epistaxis, hematuria, GI bleeding).
vWF levels below 50% are considered carriers, and vWD can be transmitted with lower levels than that.

vWD: Diagnosis

A definitive diagnosis requires assessment of vWF concentration and function.
- vWF antigen (vWF:Ag assay) is the gold standard.
- Quantitative ELISA methods use citrated or EDTA plasma.
Other diagnostic tests include electrophoresis, functional assays (e.g., aggregation, collagen binding).

Acquired Platelet Dysfunction

Acquired platelet dysfunction is often caused by drugs (e.g., NSAIDs), liver failure, renal failure, elevated globulins, and Infectious diseases (e.g., FeLV, Ehrlichia canis).
DIC (Disseminated Intravascular Coagulation): Access to fibrin degradation products (FDPs) interferes with platelet aggregation.

Secondary Hemostasis

Begins immediately after primary hemostasis, involving coagulation factors.
Amplifying, enzymatic reaction (coagulation cascade): Factors interact in a cascade, leading to insoluble fibrin deposition and clot formation.
Key parts of the coagulation cascade are the intrinsic, extrinsic, and common pathways.

Coagulation Cascade

Intrinsic pathway: Involves coagulation factors activated within the blood
Extrinsic pathway: Starts with tissue injury, initiating a coagulation cascade
Common pathway: Point when both intrinsic and extrinsic pathways converge to activate factors needed to generate fibrin.
Factors in these pathways are often vitamin K-dependent or associated with the Vitamin K pathway.

Secondary Hemostasis: Tests

PTT (partial thromboplastin time): Intrinsic and common pathways
PT (prothrombin time): Extrinsic and common pathways
Individual factor analysis: Reported as a percentage compared to a healthy control. Examples include fibrinogen concentration (heat-precipitated protein).

Disorders of the Extrinsic Pathway

Assessed via PT.
Factor VII deficiency or inhibition.
Inherited: Mostly seen in beagles, mild disease, bruising
Acquired: Associated with vitamin K deficiency or inhibition; Factor VII has shortest half-life.

Disorders of the Intrinsic Pathway

Assessed via PTT or ACT.
Factor XII deficiency: (Hageman's disease), more common in cats.
Factor XI deficiency (Hemophilia C): Mild bleeding after surgery common in dogs, Holstein cattle.

Intrinsic Pathway Disorders

Factor IX deficiency (hemophilia B): X chromosome-linked, more common in males; variable bleeding signs, internal hemorrhage may occur.
Factor VIII deficiency (hemophilia A): Most common inherited coagulation factor disorder; X chromosome-linked bleeding disorder common in males in variable ways. Hemorrhage may occur.

Common Pathway Disorders

Factor X deficiency
Fibrinogen deficiency

Multiple Pathway Disorders

Vitamin K antagonism or deficiency (effects factors II, VII, IX, X).
Liver failure (decreased production of coagulation factors).
DIC (disseminated intravascular coagulation) (consumption of factors).

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Description

Test your knowledge on the key concepts and processes of primary hemostasis. This quiz covers platelet adhesion, activation, and the coagulation cascade. Perfect for students in medical and biological sciences.