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Hematology > 5: Hemostasis- pathology, assessment & common disorders > Flashcards

5: Hemostasis- pathology, assessment & common disorders Flashcards

0
Q

How are platelets formed?

A

Hemocytoblast (stem cell)–>Megakaryoblast–>Promegakaryocyte–>Megakaryocyte–>Thrombocytes

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1
Q

What is hemostasis designed for?

A

To ensure that there is no major leakage of blood following injury & consists of a complex system of proteins & enzymes.

**any defects in these mechanisms may result in bleeding or thrombosis

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2
Q

Are platelets cells? Explain

A
  • Not cells, instead fragments of cells

- They split from huge cells in the bone marrow called Megakaryocytes and enter circulation

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3
Q

How many platelets can a single Megakaryocyte generate?

A

Around 3000 platelets, which 20-30% are pooled in the spleen (as a reservoir)

Note: NORMAL = 250,000-400,000 per cubic millimeter of blood

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4
Q

Describe a platelet

A

-Like RBCs, they have no nucleus or organelles, but contain many granules. (Content of these granules are integral components of platelets biological activities )

***LIFE SPAN= 5-20 days

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5
Q

What is the anatomy of a typical Artery?

A

1) Tunica intima (Endothelial cells, CT, Interal elastic membrane)
2) Tunica media (Smooth muscle cell)
3) Tunica exteria (or adventitia)
(Collagen & elastic fibers)

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6
Q

What is the anatomy of a “Typical” Vein

A
  • Thinner tunica media

- Presence of venous valves within endothelium

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7
Q

Anatomy of a “Typical Capillary” ?

A
  • Tunica intima only contains endothelial cells & small amt of collagen
  • ****No tunica media & no tunica externa *
  • All in all–> Very “thin-walled”
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8
Q

What is the Vasoconstrictive Phase or Vascular Spasm?

A

-The smooth muscle in damaged vessels contracts immediately producing local vasoconstriction

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9
Q

What is Vasoconstrictive Phase triggered by?

A

1) The direct injury itself

2) sympathetic nervous system

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10
Q

What is the Platelet plug formation?

A
  • Characterized by the aggregation of platelets
  • Platelets stick to exposed collagen, swell, & form spiked process
  • Platelet plugs are effective in preventing blood loss due to small injuries
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11
Q

How do Platelets stick to the exposed collagen of damaged endothelium(or artificial surface)?

A

via GPIa receptors (GP= Glycoprotein)

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12
Q

What is the von Willebrand’s Factor (vWF)?

A

A protein found in plasma, platelets & walls of blood vessels–via GPIb receptors.
**Specifically causes platelets to attach to & spread across the damaged endothelial surface

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13
Q

What is the first step of platelet formation called? What occurs?

A

ADHESION

  • Platelets undergo major structural changes & deformations
  • Adhesion also triggers the secretion of multiple factors from the platelets
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14
Q

What are the secretion factors adhesion triggers from the platelets?

A

ADP (adenosine diphosphate)
Thromboxane A2 (TA2; TXA2; prostaglandin)
Serotonin (5-HT)

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15
Q

What will ADP, TXA2 & to some extent 5-HT binding to specific receptors cause on other platelets?

A

Stimulation of these receptors will activate these platelets by making them more sticky & this adhere to one another to form an aggregate

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16
Q

Why does Aggregation occur?

A

As a consequence of another platelet glycoprotein receptor called GPIIb/IIIa onto which fibrinogen & other macromolecules bind tightly.

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17
Q

What is the Coagulation Phase (Blood Clotting) ?

A
  • Occurs either to reinforce a platelet plug or to stop bleeding when a platelet plug fails
  • Involves clotting factors
  • MOST clotting factors are made in liver (Some exceptions like Ca+2)
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18
Q

How many clotting factors are there? Where are they present?

A
  • 20 different but 12 we will study.
  • Most are present in the circulation as INACTIVE proteins (Zymogens) to prevent unwanted clotting.
  • These require activation by other clotting factors to fxn in coagulation reaction.
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19
Q

What are the Clotting factors from I-VIII?

A 
I = Fibrinogen 
II= Prothrombin
III= Tissue factor or thromboplastin 
IV= Calcium 
V= Proaccelerin (Labile factor) 
VII= Proconvertin (Stabile factor)
VIII= Antihemophilic factor A,
Antihemophilic globulin
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20
Q

What are the Clotting factors from IX-XIII?

A

IX= Antihemophilic factor B, plasma thromboplastin component
CHRISTMAS factor
X= Sturant-Prower factor
XI=Plasma thromboplastin antecedent, Hemophilia C,
ROSENTHAL SYNDROME
XII=Hageman factor
XIII=Fibrin stabilizing factor, LAKI- LORAND FACTOR

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21
Q

Which factors are vitamin K-dependent clotting factors?

A

2, 7, 9, and 10.

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22
Q

Which clotting factors are made by the liver?

A

1, 2, 5, 7, 8, 9, 10, 11,12

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23
Q

Which clotting factors are NOT made by the liver? Where are they made?

A

3, 4, 12* (liver & platelets), 13

3= Perivascular tissue
4= Plasma
13= Platelets, Plasma 
12*= Liver & Platelets
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24
Q

What is the Blood Clotting Cascade?

A

Comprises extrinsic and intrinsic pathways (both are initatiated simultaneously and lead to a “final common pathway”)

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25
Q

What is the differnce between intrinsic & Extrinsic pathway?

A 
Intrinsic= initiated within the blood (via PLATELETS) 
Extrinsic= initiated outside the blood (via TISSUE THROMBOPLASTIN)
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26
Q

What clotting factors does the intrinsic mechanism involve?

A

12, 11, 9, and 8

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27
Q

What clotting factors does the extrinsic mechanism involve?

A

Damaged perivascular tissue–>3–> 7–> 5

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28
Q

What is the path when the intrinsic and extrinsic mechanisms combine?

A

Factor X–>Prothrombin–>(Prothrombin Factor II)–>Thrombin–>(Fibrinogen Factor I)–>FIBRIN–> Fibrin Polymer

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29
Q

What are the “Natural” Anticoagulants?

A

1) Thrombomodulin
2) Antithrombin III or (Antithrombin)
3) Heparin cofactor II

  • Plasma has several protease inhibitors that rapidly inactivate coagulation factors that escape the site of injury
  • Anticoagulant system in place to maintain balance between coagulation & anticoagulation
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30
Q

What is Thrombomodulin?

A

A glycoprotein present on endothelial cells that combines w/ thrombin

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31
Q

What activates PROTEIN C, plasma protein ?

A

The Thrombomodulin-thrombin complex (Thrombin+ Thrombomodulin)

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32
Q

What is Protein C’s cofactor and what does it degrade?

A

Cofactor, PROTEIN S, degrade factors 5 and 8 (inactivates factor V & VIII)

33
Q

What is Antithrombin III (Antithrombin)

A

A glycoprotein produced by the liver that bind subsequently inhibits factor X & thrombin

34
Q

What is Heparin Cofactor II?

A

A plasma protein synthesized by the liver & inhibits THROMBIN

35
Q

What is the Fibrinolytic System?

A

After a blood clot, it allows things to be broken down to restore blood flow in a vessel.

36
Q

What is the Fibrinolytic System initiated by?

A

Initiated by the enzyme PLASMIN which is synthesized from an inactive plasma protein synthesized by the liver called PLASMINOGEN

37
Q

What is Tissue Plasminogen Activator (t-PA)?

A

-Converts plasminogen to the active plasmin, allowing fibrinolysis to occur.
-Released into the blood slowly by the damaged endothelium of the blood vessels, such that, after several days the clot is broken down.
(This occurs b/c plasminogen became entrapped within the clot when it formed; as it is slowly activated, it breaks down the fibrin mesh. )

38
Q

What are Fibrinolysis Inhibitors?

A
  • required in vivo to prevent prolonged or unwanted degradation of fibrinogen.
    1) Plasminogen activator inhibitor 1
    2) Plasminogen activator inhibitor 2
    3) Alpha 2 antiplasmin
    4) Alpha 2 macroglobulin
39
Q

What is Thrombocytopenia?

A

Low platelet count–> Increased risk for bleeding

40
Q

What is Petechia?

A

Low platelet levels that lead to bruising, particularly purpura in the forearms, (pinpoint hemorrhages on skin & mucous membranes), nosebleeds and/or bleeding of gums

41
Q

How can one confirm the automated platelet count ?

A

Blood smear/ CBC- Platelet count

***This allows the morphology of the platelets to be assessed; some inherited platelets disorders are associated w/ large platelets.

42
Q

What are Coagulation Tests (assessments for clotting system? )

A

Used to determine the function of the intrinsic & extrinsic components of coagulation system.

  • Blood is placed into tubes containing sodium citrate.
  • **Citrate binds calcium–> blood will not form a clot inside tube until further calcium is added (which is required for normal functioning of the coagulation cascade)
43
Q

What is Prothrombin Time (PT); PRO-TIME?

A

Used to assess the EXTRINSIC PATHWAY
-Calcium is added to plasma to replace that removed by citrate & brain thromboplastin is added to substitute for tissue factor.

***Clotting takes 12-15 seconds & test time is compared w/ a standart normal control in a ratio

44
Q

What is the International Normalized Ration (INR)?

A

Due to differences between different batches & manufacturers of tissue factors (it is biologically obtained product

**Devised to standardize the results. ISI says how their tissue factor compares to the other company’s. The INR is the ration of a patient prothrombin time to a normal (control) sample, raised to the power of ISI

45
Q

What is the formula for INR?

A

INR= (PTtest/PT normal)^ISI

46
Q

What is an INR?

A

MOST OFTEN used to monitor the effectiveness of drug such as WARFARIN(COUMADIN)

47
Q

What is Coumadin?

A

Anti-coagulant which means it inhibits the formation of blood clots.

**Prescribed on a long-term basis to patients who have developed recurrent inappropriate blood clotting (Heart attacks, strokes, and deep vein thrombosis)

48
Q

Why might Anti-coagulates given as a preventative measure?

A

In patients who have artificial heart valves & on a short term basis to patients who have had surgeries (knee replacements)

49
Q

Why must patient on Anti-coagulants be monitored?

A

To maintain a balance between preventing clots & causing excessive bleeding.

50
Q

What is the range of INR patients should have?

A

2.0-3.0 for basic “blood thinning” needs”

***High risk of clot formation value of INR needs to be HIGHER about 2.5-3.5.

51
Q

What is the Activated Partial Thompoplastin Time )APTT)

A

Used to assess the INTRINSIC PATHWAY

-Calcium is added to plasma to reduce that removed by citrate & then kaloin and phospholipids are aded to substitute for contact factor.

**Takes 25-36 seconds

52
Q

What is the APTT test clinically most often used for?

A

To monitor HEPARIN therapy.

***Therapeutic levels of UFH will be prolonged to 2-2.5 times that of the normal value

53
Q

What is the Thrombin clotting time (TT)

A
  • Used to asses the COMMON PATHWAY
  • Calcium is added to plasma to replace that removed by citrate & then thrombin is added to substitute for the products of the intrinsic & extrinsic pathways–> this assesses the conversion of FIBRINOGEN to FIBRIN
54
Q

Clinically what is TT used for?

A

Used when a PT and/or APTT test is prolonged, particularly if abnormal fibrinogen level or function is considered

55
Q

What are Coagulation factor assays used for?

A

To determine actual deficiencies of specific clotting factors

56
Q

What is Hemophilia A (Factor VIII Deficiency) ? Where is the mutation?

A

-X-linked disorder; mutations in factor 8 gene

**Prolongation of APTT; Pt is normal

57
Q

In Hemophilia A who is affected more commonly?

A

Affects 1 in 5000 makes (due to 1 chromosome)

-Approx 30% of patients have no family history; their disease is presumably caused by NEW MUTATIONS

58
Q

What does the % ACtivity of 8 for mild, moderate and severe?

A 
Mild= 5%-25%
Moderate= 1%-5%
Severe= <0.5%
59
Q

What is Hemophilia B (Christmas Disease) ? Where is the mutation?

A
  • X-lined disorder; Mutation is factor 9 gene

- Prolongation of APTT; PT is normal

60
Q

In Hemophilia B who is affected more commonly?

A

Affects 1 in 30,000 Males

61
Q

What are the clinical feature of Hemophilia?

A

Leads to an increased risk of prolonged bleeding form common injures , or severe causes bleeds may be spontaneous and w.out obvious causes.

62
Q

In Hemophilia where can bleeding occur?

A

May occur anywhere in the body

***superficial bleding such as those by abrasion or shallow lacerations may be prolonged & the scab may easily be broken up due to the lack of fibrin, which may because re-bleeding.

63
Q

What are the most serious sites of bleeding for a Hemophiliac?

A

1) Joint capsule
2) Skeletal muscles
3) SI tract
4) Bran

64
Q

What are other clinical feature of Hemophilia?

A

No life threatening

-JOINT BLEEDS ARE MOST SERIOUS symptoms of hemophilia

65
Q

What does repeated bleeding cause in Hemophiliacs?

A

Repeated bleeding into a joint capsule can causes permanent joint damage and disfigurement result in chronic arthritis and disability.

***Joint damage is NOT a result of blood in the capsule but rather the healing process.

66
Q

What happens when blood in the joint is broken down by enzymes in the body?

A

The bone area is also degraded .

**this exert massive amounts of pain the person afflicted w/ the disease.

67
Q

What is the Treatment for Hemeophila?

A

Patients w/ very low factor levels, who experience repeated & painful bleed into their joints & skeletal muscles, and given IV factor replacement.

**APART from “ROUTINE “ Supplementation, extra factor replacement is given around surgical produces after trauma.

68
Q

What is Von Willebrand’s Disease (vWD) ?

A

Most common inherited bleeding disorder–> affects 125 per million

**Leads to mild bleeding disorder affecting males & females equally

69
Q

What is the 2 major roles of Von Willebrand’s Disease (vWD) ?

A

1) Mediating platelet adhesion

2) Stabilizing factor 8

70
Q

In Von Willebrand’s Disease (vWD) why is bleeding typically seen in the skin & mucous membranes?

A

Because of high capillary density; these tissues particularly depend on the effiecient formation of platelet plugs to stop bleeding

71
Q

Like Hemophilia A, Von Willebrand’s Disease (vWD) also results in a prolonged APTT & reducted factor 8 clotting activity. Why is this?

A

Because of its link to factor 8, and low levels of vWF.

72
Q

vMF like hemophilia A also results in a prolonged APTT & reduced factor 8 clotting activity. How do they differ?

A

Unlike Hemophilia A, patients have prolonged PT because of a failure in platelet- vessel wall interaction.

73
Q

What is Thrombocytopenia caused by?

A

1) Impaired production of platelets which can be a) drug induced or b) Bone marrow failure

2) Increased destruction of platelets
* *Idiopathetic thrombocytopenic purpura (ITP)

74
Q

Why is Idiopathetic thrombocytopenic purpura (ITP) caused?

A

Autoimmune response to platelets, which are removed prematurely by the reticuloendothelial system

75
Q

What is Thrombophillas associated with?

A

Conditions associated with excessive clotting

76
Q

When is a Hyper-coagulable state and Potential venous thromboembolism (VTE) seen?

A

When the fibrinolytic events has a defect or deficiency in one of the natural anticoagulants will swing the balance towards these conditions.

77
Q

What are examples of Inherited thrombophilas ?

A

1) Protein C Deficiency
2) Protein S Deficiency

*These inactive Activated Factor 5 & 8

78
Q

What are examples of inherited Thrombophillas?

A

1) Activated Protein C Resistance

2) Antithrombin III Deficiency

79
Q

What causes Activated Protein C resistance?

A
  • No protein C deficiency, but instead a poor response by FACTOR 5 to PROTEIN C occurs
  • A mutation in the Factor 5 (Factor 5 Leiden) was identified as the major cause

Note: Studies have found that 5% of Caucasians in North America have factor 5 Leiden

Hematology (8 decks)

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