Patho: Chapter 22 (Disorders of Hemostasis)

Where do platelets (or thrombocytes) come from?

Large fragments of megakaryocytes in bone marrow.

What stimulates platelet (thrombocyte) production?

Thrombopoietin

Where is thrombopoietin produced?

• Liver

• Kidneys

• Smooth muscle

• Bone marrow

Where are platelets (thrombocytes) stored?

Spleen

What does vWF (von Willebrand factor) do?

It helps platelets stick to exposed collagen at the site of a blood vessel injury, allowing a platelet plug formation during clotting.

What produces vWF (von Willebrand factor)?

• Megakaryocytes

• Endothelial cells

What is hypercoagulability?

An exaggerated form of hemostasis in which there is increased clotting or platelet activity, leading to an increased risk of thrombosis and blood vessel occlusion.

What are the two forms of hypercoagulability?

• Increased platelet function

• Accelerated coagulation system activity

What does an increase in platelet function do to the body?

It results in blood flow disturbances, endothelial damage, and increased platelet aggregation

What effects do athersclerotic plaques have on blood flow?

They disturb blood flow, causing endothelial damage and promoting platelet adherence.

What does smoking, elevated levels of blood lipids and cholesterol, and diabetes mellitus do to blood vessels?

These conditions predispose a person to blood vessel damage, platelet adherence, and eventual thrombosis.

What triggers thrombus formation?

• Hypercoagulability due to increased platelet function

• Increased coagulation system activity

What can cause thrombus formation from activation of the coagulation system?

• Factor V mutation

• Prolonged bedrest

• smoking

What happens when a person is on prolonged bedrest?

It can lead to venous stasis, increasing the risk of hypercoagulability and thrombus (blood clot) formation.

What is venous stasis?

Slowed or stagnant blood flow in the veins

What is factor V Leiden?

An inherited mutation of clotting factor V that can’t be inactivated by protein C. It increases the risk of blood clot formation due to the clotting process becoming harder to regulate.

What effect do polcythemia and sickle cell disease have on blood flow?

They increase blood viscosity and resistance to blood flow, which can cause small-vessel stasis.

What causes thrombocytopenia (decreased platelet levels)?

• Decreased production

• Increased destruction

• Platelets being used up to form clots

What impairs platelet function?

• Inherited disorders of platelet adhesion (von Willebrand disease)

• Certain drugs (aspirin, heparin, NSAIDS)

• Disease

• Surgery

What is von Willebrand disease?

An inherited bleeding disorder caused by a deficiency or defect in von Willebrand factor (vWF).

What does von Willebrand disease cause?

• Decreased platelet adhesion

• Impaired clotting

• Increased risk of bleeding

Is hemophili A a X linked recessive disorder?

Yes

Why does a vitamin K deficieny cause bleeding?

It is required for clotting.

What are the 3 steps of hemostasis?

• Vascular spasm

• Platelet aggregation (platelet plug formation)

• Coagulation

What occurs during vascular spasm?

Blood vessels constrict after injurt to reduce blood loss.

What occurs during platelet aggregation (platelet plug formation)?

Platelets stick to exposed collagen with the help of von Willebrand factor (vWF), become activated, and release chemicals that attract more platelets to form a platelet plug.

What occurs during coagulation?

Fibrin strands form a mesh that traps red blood cells and platelets to create a stable blood clot.

What are the 3 steps of coagulation?

• Phase 1

• Phase 2

• Phase 3

What occurs during phase 1 of coagulation?

Intrinsic and extrinsic pathways activate clotting factors, leading to the formation of prothrombin activator.

What occurs during phase 2 of coagulation?

Prothrombin activator converts prothrombin into thrombin.

What occurs during phase 3 of coagulation?

Thrombin converts fibrinogen into fibrin strands, which form the blood clot.

What causes a vitamin K deficiency?

• Insufficient intestinal flora

• Antibiotics

• Poor dietary intake

What happens to coagulation factor synthesis in liver or gallbladder diseases?

Synthesis of coagulation factors II, V, VII, IX, X, XI, XII, and fibrinogen are reduced.

What is Disseminated Intravascular Coagulation (DIC)?

A condition involving both excessive clotting and excessive bleeding due to widespread activation of the coagulation cascade.

What causes Disseminated Intravascular Coagulation (DIC)?

• Postpartum complications

• Trauma

• Sepsis

• Cancer

What does the massive activation of coagulation cascade and generation of microthrombi cause?

• Vessel occlusion (blockages)

• Tissue ischemia

What are microthrombi?

Tiny blood clots that form within small blood vessels.

What are the effects of microthrombi formation in Disseminated Intravascular Coagulation (DIC)?

They consume all available coagulation proteins and platelets which cause hemorrhaging and hypertension.

What is Hemophilia A?

An inherited X-linked bleeding disorder which impairs blood clotting and increases bleeding risk

What causes Hemophilia A?

A deficiency of clotting factor VIII

All of the following are true EXCEPT:

Polycythemia decreases the resistance to blood flow and this decreases blood viscoity and leads to clots.

A 42-year-old male client recently diagnosed with liver cancer is noted at highrisk for bleeding abnormalities. The nurse recognizes this risk as a result of:

The reduction of clotting factors synthesized in the liver.

Following a lecture on hemostasis, a nursing student accidently cuts her hand while preparing supper for her family. She watches the laceration quickly close. Sure enough, the first thing she notes is:

Initially, it takes a few seconds for blood to appear as a result of vessel spasm