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Pathology - Exam III > Coagulation I, II, III (2/20 & 2/27, Thienelt) > Flashcards

Coagulation I, II, III (2/20 & 2/27, Thienelt) Flashcards

1
Q

Define hemostasis:

A

Process whereby an injury to a blood vessel triggers a series of enzymatic reactions.

Results in the formation of platelet and fibrin plugs at the site of the injury.

Carefully controlled so that the clot does not cause detriment to the vascular system by dislodging.

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2
Q

What is (in general) primary hemostasis?

A

The first thing to occur in response to an injury to the vessel: a platelet plug!

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3
Q

What are the 5 steps of primary hemostasis?

A
  1. adhesion
  2. shape change
  3. granule release
  4. recruitment of more platelets
  5. aggregation
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4
Q

What takes place during the adhesion step of primary hemostasis?

A

Platelets stick to the cut vessel wall where collagen is exposed with the help of von Willebrand factor and thrombin that has been generated due to the injury.

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5
Q

What takes place during the shape change step of primary hemostasis?

A

When the platelets become stimulated, receptors for fibrinogen are exposed.

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6
Q

What takes place during the granule step of primary hemostasis?

A

The activated platelets release ADP, vasoactive amines, and form thomboxane A2.

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7
Q

What takes place during the recruitment step of primary hemostasis?

A

More platelets are recruited to the clot

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8
Q

What takes place during the aggregation step of primary hemostasis?

A

At this point, thrombin has converted fibrinogen to fibrin. Fibrin + platelets = a nice seal of platelets.

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9
Q

What does thromboxane do?

A

Contracts smooth muscle and causes vasoconstriction of the vessel at the site of the injury. –> Helps stop the leakage of blood.

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10
Q

What is the main goal of the coagulation cascade?

A

To produce thrombin!
Thrombin promotes platelet aggregation and converts fibrinogen to fibrin to create the clot.

Thrombin activates cofactors (Factors V and VIII) in the coagulation cascade.

Thrombin activates factors to lyse the clot.

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11
Q

What does Factor XIII do?

A

A tissue factor that is an enzyme that crosslinks the fibrin and hardens the fibrin clot.

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12
Q

What is the main function of secondary hemostasis?

A

Secondary hemostasis = coagulation phase.

After primary hemostasis, a platelet plug has formed that is held together with fibrinogen.

Clotting factors come together to form complexes and activate the coagulation cascade.

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13
Q

What is fibrin?

A

The glue that holds the clot together.

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14
Q

What are the basic steps of the coagulation cascade?

A

Fibrinogen —(acted on by thrombin)–>
fibrin —(acted on by factor XIII)–>
fibrin, the clot

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15
Q

What is the main role of the extrinsic pathway?

A

To generate a “thrombin burst”, a process by which thrombin is released very rapidly.

Precipitating event is exposure of tissue factor to blood.

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16
Q

What is the main role of the intrinsic pathway?

A

independent of the extrinsic path.

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17
Q

What are the basic laboratory tests to measure hemostasis?

A

PTT = partial thromboplastin time
PT = prothrombin time
INR = international normalized ratio
Bleeding time/PFA-100

18
Q

What does PT, prothrombin time, measure in a bleeding patient?

A

Measures the procoagulant activity (sensitive to vitamin K-dependent factors) of the extrinsic pathway and the lower part of the coagulation cascade. Normal = 9-12 seconds.

19
Q

What does INR, international normalized ratio measure?

A

Normalized PT value to account for variations in the lab. INR of 1.0 is a normal value.

20
Q

What does PTT, partial thromboplastin time, measure?

A

Measures the procoagulant activity of the entire pathway. Normal = 25 - 32 seconds.
Used to monitor heparin therapy.
Hemophilia = prolonged PTT

21
Q

What does bleeding time measure?

A

The platelet and vessel interaction as well as the number and the function of platelets. NOT ACCURATE and does NOT CORRELATE with bleeding complications.

Time to clot is measured.
Normally 2 - 9 minutes.

Note: PFA-100 can perform an in vitro bleeding time measurement.

22
Q

What vitamin is important in coagulation?

A

Vitamin K

Clotting factors require vitamin K and an adequately functioning liver.

23
Q

How does the drug Warfarin work?

A

Warfarin interferes with the vitamin K dependent clotting factor post-translational reaction.

24
Q

What is plasmin?

A

Enzyme that degrades fibrin.

25
Q

What are antithrombin III and proteins C and S?

A

Natural anticoagulants

26
Q

What is a mouthwash ingredient that helps slow prolonged bleeding?

A

Amicocaproic acid: Amikar. Inhibits plasmin (which destroys clots) and is antifibrinolytic

27
Q

What does the Thrombin Time test measure?

A

The rate of conversion of fibrinogen to fibrin upon the addition of excess thrombin to plasma.

Prolonged = low or abnormal fibrinogen

28
Q

Name 3 congenital bleeding disorders:

A
  1. Von Willegrands Disease
  2. Hemophilia A and B
  3. Various factor deficiencies
29
Q

What are the basic components of a bleeding history?

A

Need a detailed history because a patient may not know what is excessive bruising or bleeding:

  1. Ask common questions: nosebleeds, dental work bleeding, surgeries, bruises, menstrual periods, bleed when brushing teeth?
  2. Family history
  3. drugs
  4. illnesses
30
Q

What is the typical physiologic function of the von Willebrand protein?

A

The von Willebrand protein circulates in the plasma and:

  1. adheres platelets to exposed collagen at site of wound. Disease = prolonged bleeding times.
  2. carries Factor VIII. Without von Willegrand protein, Factor VIII has a very short half-life. Disease = prolonged partial thromboplastin time (PTT).
31
Q

What are the typical bleeding symptoms of von Willebrand disease?

A

Patients often bleed from mucosal membranes and have many nosebleeds, GI bleeds, and bleed after surgery.

32
Q

What are the symptoms of severe hemophilia?

A

Hemophilia A = factor VIII deficiency.

Severe hemophilia = spontaneous hemorrhaging in joints, muscles, soft tissues, retroperitoneal space, and sometimes the CNS.

With no treatment, have severe arthritis and usually early death.

33
Q

What are the clinical differences between hemophilia A and B?

A

The clinical symptoms are identical.

34
Q

What causes hemophilia A?

A

Factor VIII deficiency

35
Q

What causes hemophilia B?

A

Factor IX deficiency (not as common as A)

36
Q

How are the hemophilia diseases inherited?

A

They are X-linked, so there are carrier females.

37
Q

How is von Willebrand disease inherited?

A

Autosomal dominant –> occurs equally in men and women.

38
Q

How is hemophilia (both A and B) treated?

A

Use recombinant or purified factor products. Very effective in preventing or stopping bleeding.

39
Q

How is von Willebrand treated?

A

Use DDAVP (arginine vasopressin) is a very effective treatment in type I where there is simply a deficiency of normal von Willebrand protein.

40
Q

What are the three mechanisms that can lead to low platelet counts?

A
  1. Decreased production of platelets
  2. Increased destruction of platelets
  3. Distribution/Dilution disorders
41
Q

What type of disorder is thrombocytopenia?

A

An acquired bleeding disorder.

It results in a decreased number of platelets.

42
Q

What are some medications that inhibit platelet function?

A

Chemotherapy
Antibiotics
Thiazide diuretics
Radiation

Pathology - Exam III (4 decks)

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