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Bood and Lymph > Hemostasis and related disorders > Flashcards

Hemostasis and related disorders Flashcards

1
Q

Describe primary hemostasis

A
  • vWB factor (released from Weibel-Palade bodies of endothelial cells and alpa-granules of platelets) binds to exposed collagen.
  • GP1b receptor of platelets binds vWF inducing degranulation
  • ADP is released stimulating expression of GP2b3a
  • TXA2 is released stimulating platelet aggregation
  • GP2b3a receptors bind fibrinogen forming weak platelet plug that is then stabilized by coagulation cascade
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2
Q

Name the primary hemostasis disorders

A
  • Immune thrombocytopenic purpura (ITP)
  • Microangiopathic hemolytic anemias (thrombic thrombocytic purpura (TTP) and hemolytic uremic syndrome (HUS))
  • Bernard-soulier and Glanzmann thrombasthenia (qualitative platelet disorders)
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3
Q

Who gets Immune thrombocytopenic purpura (ITP)?

A
  • Most common cause of thrombocytopenia in children and adults
  • Acute, normally self limiting following infection in children
  • Chronic, appears in women of child bearing age (sometimes secondary to SLE), can be passed to fetus, temporary.
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4
Q

What are the lab findings in Immune thrombocytopenic purpura (ITP)?

A
  • Decreased platelet count <50 k
  • Normal PT/PTT
  • Increased megakaryocytes on bone marrow biopsy
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5
Q

What is the treatment for Immune thrombocytopenic purpura (ITP)?

A
  • Corticosteroids effective in children, adults normally relapse.
  • IVIG for bleeding normally short lived.
  • Spenectomy (refractory cases).
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6
Q

What causes thrombic thrombocytic purpura (TTP)?

A
  • Decrease in ADAMTS13 (an enzyme that cleaves vWF multimers for eventual degradation) normally due to autoantibodies, commonly seen in women.
  • vWF multimer leads to abnormal platelet aggregation and microthrombi formation–> Microangiopathic hemolytic anemia.
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7
Q

What is the cause of HUS?

A
  • Caused by endothelial damage by drugs or infection (verotoxin)
  • Commonly caused by E. Coli O157 H7 in children
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8
Q

What are the clinical findings of TTP and HUS?

A
  • Microangiopathic hemolytic anemia
  • Skin and mucosal bleeding and fever
  • Renal insufficiency (HUS)
  • CNS defects (TTP)
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9
Q

What are the laboratory findings for MHA?

A
  • Thrombocytopenia with increased bleeding time
  • Normal PT/PTT
  • Anemia with schistocytes
  • Increased megakaryocytes on bone marrow biopsy
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10
Q

What is the treatment for MHA?

A
  • Plasmapheresis and corticosteroids particularly in TTP
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11
Q

What is the cause of Bernard-soulier and Glanzmann thrombasthenia?

A
  • Bernard-soulier - Genetic GP1b deficiency

- Glanzmann thrombasthenia - Genetic GP2b3a deficiency

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12
Q

How does secondary hemostasis stabilize the weak platelet plug?

A
  • Coagulation cascade generates thrombin
  • Thrombin converts fibrinogen to fibrin
  • Fibrin cross linking stabilizes the platelet thrombus
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13
Q

What activates secondary hemostasis? and which pathway is activated?

A
  • Tissue factor (released by endothelial cells)–> factor 7 (extrinsic pathway, TP)
  • Subendothelial collagen–> factor 12 (intrinsic pathway, TTP)
  • Phospholipid suface of platelets and Ca
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14
Q

What causes hemophilia A?

A
  • Factor 8 deficiency (X-linked recessive, and de novo mutation)
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15
Q

How does a patient with hemophilia A present and what are the laboratory findings?

A
  • Deep tissue, joint and post surgical bleeding
  • Increased PTT, normal PT
  • Decreased factor 8
  • Normal platelets and bleeding time
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16
Q

What is the treatment for hemophilia A?

A
  • Recombinant factor 8
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17
Q

What is hemophilia B?

A
  • Factor 9 deficiency

- Resembles hemophilia A

18
Q

What is coagulation factor inhibitor? What is the most common factor? and How is it distinguished from hemophilia A?

A
  • Developed autoantibody against coagulation factor.
  • Most commonly factor 8
  • PTT does not correct when mixed with normal plasma
19
Q

What is Von Willebrand disease?

A
  • Deficiency in vWF
  • Most common inherited coagulation disorder
  • Many variants, most common of which is autosomal dominant reduction in vWF
20
Q

How does patient present with VWD?

A
  • Mild mucosal and skin bleeding

- Deep tissue, joint and post surgical bleeding typically not seen

21
Q

What are the lab findings for VWD?

A
  • Increased bleeding time
  • Increased PTT, normal PT (vWF stabilizes factor 8)
  • Abnormal rictocetin test - Induces vWF GP1b binding and platelet aggregation
22
Q

What is the treatment for VWD?

A
  • Desmopressin (ADH analog) - increases vWF release for Weibel-palade bodies and alpha granules
23
Q

How does vitamin K effect secondary hemostasis?

A
  • Epoxide reductase released by the liver actives vitamin K–> vitamin K gamma
  • Vitamin K gamma activates –> factors 2, 7, 9, 10, C, S
24
Q

When does vitamin K deficiency occur?

A
  • New borns - due to the absence of bacteria that produce vit K. Given vit K injection at birth to prevent hemorrhagic disease of the new born.
  • Malabsorption, fat soluble vitamin
  • Long-term antibiotic therapy, destruction of gut bacteria
25
Q

What are other causes of secondary hemostasis and why do they occur?

A
  • Liver disease - decreased production of coagulation factors and epoxide reductase (no activation of vitamin K)
  • Large volume transfusions - dilution leads to relative deficiency
26
Q

How does heparin induced thrombocytopenia occur?

A
  • Heparin therapy induces platelet destruction causing the release of cytokines causing the activation of the remaining platelets–> thrombus
27
Q

What are the causes of DIC?

A
  • Obstetric complications –> Tissue thromboplastin from fetus into maternal blood–> coagulation
  • Sepsis (E. Coli, N. menengitidis) - Endotoxin and cytokines (IL-1 and TNF) –> TF production
  • Adenocarcinoma –> Mucin –> coagulation
  • Acute promyelocytic leukemia –> Primary granules actives coagulation
  • Rattlesnake bite –> venom activates coagulation
28
Q

What are the laboratory findings for DIC?

A
  • Decrease platelet count
  • Increase PT/PTT
  • Decrease fibrinogen
  • Increase fibrin split products
  • Microangiopathic hemolytic anemia
29
Q

What is the treatment for DIC?

A
  • Blood products and cryoprecipitate (contains coagulation factors)
30
Q

What is the normal mechanism of fibrinolysis?

A
  • Tissue plasminogen activator converts plasminogen to plasmin which cleaves fibrin and fribrinogen, destroys coagulation factors and blocks platelet aggregation
  • Alpha-2 antiplasmin breaks down plasmin
31
Q

What causes fibrinolysis disorders and what are some examples?

A
  • Plasmin overactivity
  • Radical prostatectomy- urokinase release
  • Cirrhosis of the liver- decreased production of alph-2 antiplasmin
32
Q

What are the laboratory findings for disorders of fibrinolysis?

A
  • Increased PT/PTT
  • Increased bleeding time with no increase in platelets
  • Increased fibrinogen split products with no D-dimers
33
Q

How do patients present with disorders of fibrinolysis?

A
  • Increased bleeding resembling DIC
34
Q

How are disorders of fibrinolysis treated?

A
  • Aminocaproic acid which blocks activation of plasminogen
35
Q

How is a thrombus differentiated from postmortem clot?

A
  • Lines of Zahn

- Attachment to vessel wall

36
Q

What are the three major risk factors in thrombus formation?

A
  • Disruption in blood flow
  • Endothelial cell damage
  • Hypercoagulable state
37
Q

What are examples of disruption in normal blood flow?

A
  • Immobilization
  • Cardiac wall disfunction
  • Aneurysm
38
Q

By what mechanisms do endothelial cells prevent coagulation?

A
  • Block subendothelial collagen
  • PGI2 and NO: vasodilation and platelet inhibition
  • Secrete heparin like molecule: augment antithrombin 3 –> inactivates thrombin and coagulation factors
  • Secrete tissue plasminogen activator
  • Secretes thrombomodulin–> redirects thrombin to activate protein C –> inactivvation of 5 and 8
39
Q

What are some contributing factors to endothelial damage?

A
  • B12, folate and cystathionine beta synthase (CBS) deficiency –> increased levels of homocysteine
40
Q

What factors contribute to hypercoagulabe state?

A
  • Protein C or S deficiency
  • Factor 5 Leiden
  • Prothrombin 20210A
  • Antithrombin 3 deficiency
  • Birthcontrol
41
Q

What causes immune thrombocytopenic purpura?

A
  • IgG antibodies against platelet antigens (GP1b, GP2b/3a)

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