Understanding Bleeding Tendency in Children

Questions and Answers

What is the primary role of von Willebrand factor (VWF) in hemostasis?

To activate factor VII in the coagulation cascade

To remove the clot through fibrinolysis

To enable platelet adhesion (correct)

To form a stable fibrin clot

Which pathway in the coagulation cascade is activated by factor IXa?

Extrinsic pathway

Fibrinolytic pathway

Common pathway

Intrinsic pathway (correct)

What is the main characteristic of activated partial thromboplastin time (aPTT)?

It assesses the intrinsic pathway of coagulation (correct)

It tests the extrinsic pathway of coagulation

It is used to detect platelet dysfunction

It measures fibrinolytic activity

What is a limitation of using bleeding time as a diagnostic tool?

It has low specificity and sensitivity Signup and view all the answers

What function does thrombin serve in the coagulation process?

Converts fibrinogen into an insoluble fibrin clot Signup and view all the answers

What initiates the formation of the platelet plug during hemostasis?

Binding of GPIb to von Willebrand factor (VWF) Signup and view all the answers

Which test is used to evaluate the intrinsic pathway of coagulation?

Activated partial thromboplastin time (aPTT) Signup and view all the answers

What is the final step in the coagulation cascade leading to clot formation?

Activation of factor X to convert prothrombin to thrombin Signup and view all the answers

Which of the following is a characteristic of the coagulation cascade's extrinsic pathway?

Involves the activation of factor VII Signup and view all the answers

What is the role of fibrinolysis in hemostasis?

To remove the clot following hemostasis Signup and view all the answers

Study Notes

Learning Objectives

Understand normal hemostasis physiology.
Identify causes of bleeding disorders in children.
Establish a systematic diagnosis approach for pediatric bleeding.
Recognize common bleeding disorders through clinical and laboratory methods and understand management strategies.

Normal Hemostasis

Hemostasis consists of several phases: vasoconstriction, platelet plug formation, coagulation, and clot removal.

Phases of Hemostasis

Vasoconstriction: Initial response to vascular injury to reduce blood flow.
Platelet Plug Formation:
- Platelet Adhesion: Platelets bind to von Willebrand factor (VWF) via GPIb receptor.
- Platelet Aggregation: Platelets clump together using GPIIb/IIIa receptor to bind fibrinogen.
- Assessment of this function includes platelet count, platelet function tests, and VWF assays.
- Historical use of bleeding time is subjective and has low sensitivity and specificity.

Coagulation Cascade

Intrinsic Pathway: Activated by factor IXa in the presence of factor VIIIa, leading to factor X activation; assessed by aPTT.
Extrinsic Pathway: Activated by factor VII (factor VIIa) with tissue factor, also leading to factor X activation; assessed by PT.
Common Pathway: Both intrinsic and extrinsic pathways culminate in factor X activation, converting prothrombin to thrombin.
- Thrombin transforms fibrinogen into insoluble fibrin, forming a stable clot.
- Thrombin time (TT) measures this process.
- Factor XIII activates to convert unstable fibrin into a stable clot.

Clot Removal

Clots are eventually removed through a process called fibrinolysis.

Learning Objectives

Understand normal hemostasis physiology.
Identify causes of bleeding disorders in children.
Establish a systematic diagnosis approach for pediatric bleeding.
Recognize common bleeding disorders through clinical and laboratory methods and understand management strategies.

Normal Hemostasis

Hemostasis consists of several phases: vasoconstriction, platelet plug formation, coagulation, and clot removal.

Phases of Hemostasis

Vasoconstriction: Initial response to vascular injury to reduce blood flow.
Platelet Plug Formation:
- Platelet Adhesion: Platelets bind to von Willebrand factor (VWF) via GPIb receptor.
- Platelet Aggregation: Platelets clump together using GPIIb/IIIa receptor to bind fibrinogen.
- Assessment of this function includes platelet count, platelet function tests, and VWF assays.
- Historical use of bleeding time is subjective and has low sensitivity and specificity.

Coagulation Cascade

Intrinsic Pathway: Activated by factor IXa in the presence of factor VIIIa, leading to factor X activation; assessed by aPTT.
Extrinsic Pathway: Activated by factor VII (factor VIIa) with tissue factor, also leading to factor X activation; assessed by PT.
Common Pathway: Both intrinsic and extrinsic pathways culminate in factor X activation, converting prothrombin to thrombin.
- Thrombin transforms fibrinogen into insoluble fibrin, forming a stable clot.
- Thrombin time (TT) measures this process.
- Factor XIII activates to convert unstable fibrin into a stable clot.