Ch. 14 - Disorders of Platelets, Hemostasis, and Coagulation

Pathophysiology Exam 2

What is hemostasis?

The normal process that stops bleeding after blood vessel injury while maintaining blood flow through intact vessels

What are the three major steps of hemostasis?

Vasoconstriction, platelet plug formation (primary hemostasis), and coagulation with fibrin clot formation (secondary hemostasis)

What is the first response to blood vessel injury?

Vasoconstriction to reduce blood flow to the injured area

Why is vasoconstriction important after vessel injury?

It decreases blood loss until a clot can form

What is primary hemostasis?

The formation of a temporary platelet plug at the site of blood vessel injury

What role do platelets play in hemostasis?

They adhere to the injured vessel, become activated, and aggregate to form the initial platelet plug

What is secondary hemostasis?

Activation of the coagulation cascade, resulting in fibrin formation that stabilizes the platelet plug

What is fibrin?

An insoluble protein that forms a mesh to strengthen and stabilize a blood clot

Which clotting protein is converted into fibrin?

Fibrinogen is converted into fibrin by thrombin

What is thrombin?

An enzyme that converts fibrinogen into fibrin during coagulation

What are platelets?

Small cell fragments produced by megakaryocytic that are essential for blood clotting

Where are platelets produced?

In the bone marrow by megakaryocytes

What is the normal platelet count?

Approximately 150,000-400,000/uL

What is thrombocytopenia?

A platelet count below 150,000/uL

What is thrombocytosis?

A platelet count above the normal range?

What are common causes of thrombocytopenia?

Bone marrow suppression, chemotherapy, leukemia, immune thrombocytopenia (ITP), DIC, severe infection, and certain medications

What are the common signs and symptoms of thrombocytopenia?

Petechiae, purpura, easy bruising, bleeding gums, epistaxis, prolonged bleeding, and heavy menstrual bleeding

Why does thrombocytopenia increase bleeding risk?

There are too few platelets available to form an effective platelet plug

What are petechiae?

Tiny, pinpoint, non-blanching red or purple spots caused by bleeding into the skin

What is purpura?

Larger purple discolorations of the skin caused by bleeding under the skin

What is the coagulation cascade?

A series of clotting factor activations that ultimately produce fibrin to stabilize a blood clot

What is the function of clotting factors?

They activate one another in sequence to generate thrombin and fibrin

Where are most clotting factors produced?

The liver

Why is liver disease associated with bleeding disorders?

The liver produces most clotting factors, so impaired liver function reduces clotting factor synthesis

Why is vitamin K important?

It is required for the liver to produce several clotting factors necessary ofr normal coagulation

Which fat-soluble vitamin is essential for blood clotting?

Vitamin K

What conditions can lead to vitamin K deficiency?

Fat malabsorption, prolonged antibiotic therapy, liver disease, poor nutrition, and newborn physiology

What is the function of fibrinolysis?

To break down clots after healing has occurred and restore normal blood flow

Which enzyme breaks down fibrin?

Plasmin

Why is fibrinolysis important?

It prevents unnecessary clot persistence and helps maintain normal circulation

What is a bleeding disorder?

A condition in which normal blood clotting is impaired, resulting in excessive or prolonged bleeding

What are common signs and symptoms of bleeding disorders?

Easy bruising, petechiae, purpura, prolonged bleeding, epistaxis, bleeding gums, heavy menstrual bleeding, and excessive bleeding after surgery or injury

What is ecchymosis?

A larger area of bleeding under the skin, commonly called a bruise

What is nhemarthrosis?

Bleeding into a joint, causing pain, swelling, and decreased range of motion

Which inherited bleeding disorders commonly causes hemarthrosis?

Hemophilia

What is hemophilia?

An inherited bleeding disorder caused by deficiency or specific clotting factors

What is hemophilia A?

A deficiency of clotting factor VIII?

What is hemophilia B?

A deficiency of clotting factor IX

How is hemophilia inherited?

It is usually inherited as as X-linked recessive disorder, primarily affecting males

Why do patients with hemophilia bleed excessively?

They cannot form a stable fibrin clot because they lack a key clotting factor

What are common signs and symptoms of hemophilia?

Prolonged bleeding, easy bruising, nhemarthrosis, muscle bleeding, and excessive bleeding after procedures or trauma

What is the most serious complication of hemophilia?

Intracranial hemorrhage or severe internal bleeding

How is hemophilia diagnosed?

Bly clotting factor says and coagulation studies, typically showing a prolonged aPTT with a normal PT/INR

How is Hemophilia A treated?

Replacement of factor VIII concentrates

How is Hemophilia B treated?

Replacement of factor IX concentrates

What is von Willebrand disease (vWD)?

The most common inherited bleeding disorder, caused by a deficiency or dysfunction of von Willebrand factor (vWF)

What is the function of von Willebrand factor?

It helps platelets adhere to damaged blood vessels and protects factor VIII from breakdown

Why does von Willebrand disease cause bleeding?

Platelets cannot adhere effectively to the injured vessel, and factor VIII levels may be reduced

What are common signs and symptoms of von Willebrand disease?

Frequent nosebleeds, easy bruising, bleeding gums, prolonged bleeding after dental work or surgery, and heavy menstrual bleeding

How is von Willebrand disease difference from hemophilia?

von Willebrand disease primarily affects platelet adhesion, while hemophilia affects the coagulation cascade. Hemarthrosis is much less common in vWD

How is mild von Willebrand disease commonly treated?

Desmopressin (DDAVP), which stimulates release of stored von Willebrand factor and factor VIII

How are more severe cases of von Willebrand disease treated?

von Willebrand factor-containing concentrates and supportive management

What does Prothrombin Time (PT) evaluate?

The extrinsic and common pathways of the coagulation cascade

What is the International Normalized Ratio (INR)?

A standardized way to report PT results and monitor warfarin therapy

Which medication is monitored using the INR?

Warfarin

What does Activated Partial Thromboplastin Time (aPTT) evaluate?

The intrinsic and common pathways of the coagulation cascade

Which medication is monitored using the aPTT?

Unfractionated heparin

Which coagulation test is prolonged in hemophilia?

aPTT

Which coagulation test is typically normal in hemophilia?

PT/INR

Why are PT/INR and aPTT important?

They help identify coagulation abnormalities and monitor anticoagulant therapy

What is Disseminated Intravascular Coagulation (DIC)?

A life-threatening disorder in which widespread activation of the coagulation cascade causes excessive clot formation throughout the body, consuming platelets and clotting factors and leading to severe bleeding

Why id DIC called a “consumptive coagulopathy”?

Because platelets and clotting factors are rapidly consumed while forming widespread clots, leaving too few available to control bleeding

What commonly triggers DIC?

Severe sepsis, major trauma, obstetric complications (such as placental abruption or amniotic fluid embolism), malignancy, severe burns, and massive tissue injury

How does DIC affect the body’s organs?

Tiny clots block blood flow in small vessels, reducing oxygen delivery and potentially causing organ ischemia and failure

Why do patients with DIC bleed excessively?

Platelets and clotting factors become depleted after being consumed by widespread clot formation

What are common signs and symptoms of DIC?

Petechiae, purpura, oozing from IV sites, bleeding gums, hematuria, gastrointestinal bleeding, bruising, and signs of organ dysfunction

What laboratory findings are commonly seen in DIC?

Low platelet count, prolonged PT, prolonged aPTT, low fibrinogen, and elevated D-dimer

What is D-dimer?

A fibrin degradation product that indicates recent clot formation and breakdown

Why is the D-dimer elevated in DIC?

Because widespread clot formation is followed by increased fibrinolysis, producing large amounts of fibrin breakdown products

What is the primary treatment for DIC?

Treat the underlying cause while providing supportive care, including blood products when indicated

Why is treating the underlying cause essential in DIC?

DIC will usually continue until the triggering condition is controlled or resolved

When are platelet transfusions used?

In patients with severe thrombocytopenia who are actively bleeding or at high risk for bleeding

What is Fresh Frozen Plasma (FFP)?

Plasma containing clotting factors that is used to replace deficient clotting proteins

When is Fresh Frozen Plasma commonly administered?

During significant bleeding associated with multiple clotting factor deficiencies, including DIC or warfarin-associated bleeding when appropriate

What is cryoprecipitate?

A blood product rich in fibrinogen, factor VIII, factor XIII, and von Willebrand factor

When is cryoprecipitate commonly used?

When fibrinogen levels are critically low, such as in severe DIC

Why is fibrinogen important?

It is converted into fibrin, which stabilizes blood clots

What is the treatment for vitamin K deficiency bleeding?

Vitamin K replacement and treatment of the underlying cause

What medication reverses the effects of warfarin?

Vitamin K. In life-threatening bleeding, additional therapies such as prothrombin complex concentrate (PCC) or FFP may also be used

What medication can reverse the effects of unfractioned heparin?

Protamine sulfate

What is hypercoagulable state?

A condition in which the blood has an increased tendency to clot

Why are hypercoagulable disorders dangerous?

They increase the risk of DVT, pulmonary embolism, stroke, and myocardial infarction

What inherited condition is a common cause of increased clotting risk?

Factor V Leiden mutation

What acquired factors increase the risk of abnormal clotting?

Surgery, trauma, prolonged immobility, pregnancy, estrogen therapy, cancer, obesity, and smoking

Why does prolonged mobility increase the risk of DVT?

Decreased muscle contraction slows venous blood flow, promoting clot formation

What are common symptoms of a deep vein thrombosis (DVT)?

Unilateral leg swelling, pain, warmth, redness, tenderness

What complication can occur if part of a DVT breaks loose?

A pulmonary embolism

What are common signs and symptoms of a pulmonary embolism?

Sudden shortness of breath, pleuritic chest pain, tachycardia, hypoxemia, and sometimes coughing up blood (hemoptysis)

How are hypercoagulable disorders commonly treated?

Anticoagulant medications and management of underlying risk factors

What is the overall goal of anticoagulant therapy?

To reduce the formation and extension of blood clots while balancing the risk of bleeding

Which laboratory test is most useful for evaluating platelet number?

Platelet count on the Complete Blood Count (CBC)

Which laboratory test evaluates the extrinsic coagulation pathway?

Prothrombin Time, reported as the International Normalized Ratio

Which laboratory test evaluates the intrinsic coagulation pathway?

Activated Partial Thromboplastin Time

Which coagulation test is monitored for patients receiving warfarin?

PT/INR

Which coagulation test is monitored for patients receiving unfractionated heparin?

aPTT

What is the major difference between a platelet disorder and a clotting factor disorder?

platelet disorders impair formation of the initial platelet plug (primary hemostasis), while clotting factor disorders impair formation of a stable fibrin clot (secondary hemostasis)

Which disorder is more likely to cause petechiae and mucosal bleeding?

Thrombocytopenia

Which disorder is more likely to cause hemarthrosis?

Hemophilia

Why do platelet disorders commonly cause nosebleeds and bleeding gums?

Platelets are especially important for preventing bleeding from small blood vessels in mucous membranes

Why are joint bleeds more common in hemophilia?

Deficiency of clotting factors prevents formation of a stable fibrin clot, allowing bleeding into deep tissues and joints