Hemostasis Flashcards
1
Q
What is the primary function of clot regulators?
A
To turn down or turn off the clotting process to prevent over-clotting
This is achieved through a series of inhibitors.
2
Q
What are Protein C and Protein S dependent on?
A
Vitamin K
They are synthesized in the liver.
3
Q
What does Activated Protein C (APC) inhibit?
A
Factors Va and VIIIa
4
Q
What is the consequence of a deficiency in Protein C or S?
A
Increased risk of thrombosis, especially DVT or pulmonary embolism
5
Q
What can cause acquired deficiencies of Protein C and S?
A
- Decreased production due to liver disease or vitamin K deficiency
- Excessive loss due to kidney disease
6
Q
What is the major inhibitor of coagulation?
A
Anti-Thrombin III
7
Q
How does Antithrombin III function?
A
It inactivates thrombin and factors of the intrinsic pathway
8
Q
What enhances the activity of Antithrombin III?
A
Heparin
9
Q
What is the role of Tissue Factor Pathway Inhibitor (TFPI)?
A
Inhibits tissue factor-FVIIa complex, thereby inhibiting the extrinsic pathway
10
Q
What is Thromboxane’s role in coagulation?
A
It is a procoagulant that promotes platelet aggregation and vasoconstriction
11
Q
What does Antiplasmin do?
A
Inactivates plasmin rapidly and factors XI and XII slowly
12
Q
What anticoagulant is used for collecting coagulation specimens?
A
Sodium Citrate
13
Q
What is the proper blood to anticoagulant ratio for coagulation testing?
A
1:9 liquid anticoagulant: whole blood
14
Q
What factors does PT/INR measure?
A
Extrinsic and common pathway factors: II, V, VII, X
15
Q
What factors does aPTT measure?
A
Intrinsic and common pathway factors: XII, XI, IX, VIII, X, V, II, I
16
Q
What is the normal range for PT/INR?
A
0.9-1.2
17
Q
What is the only factor not assessed by PT or aPTT?
A
Factor XIII
18
Q
What is the purpose of mixing studies in coagulation testing?
A
To determine if a patient’s plasma is factor deficient or inhibited
19
Q
What two methods are currently used for factor assays?
A
- Clotting assays
- Chromogenic assays
20
Q
What does the Chromogenic Assay measure?
A
The ability of a specific factor to cleave a chromogenic-linked substrate
21
Q
What condition is associated with decreased fibrinogen levels?
A
Liver failure or DIC
22
Q
What is Dysfibrinogenemia?
A
A rare condition where fibrinogen levels are normal but dysfunctional
23
Q
What is the significance of a high fibrinogen level?
A
It indicates tissue injury, inflammation, or infection
24
Q
What does a low fibrinogen concentration affect?
A
Both PT and PTT as well as any clot-based assays
25
What happens during the double spin process in coagulation testing?
Plasma is removed carefully to avoid disturbing the buffy coat
26
What is the consequence of having afibrinogenemia?
Little to no fibrin formation
27
What is the most commonly used antiplatelet drug?
Aspirin
## Footnote
Aspirin irreversibly blocks platelet activation and aggregation.
28
How long does it take for aspirin to eliminate its effects on platelets?
7-10 days
## Footnote
Important for surgical patients.
29
What is primary hemostasis?
Temporary platelet plug formation
## Footnote
Involves vasoconstriction, platelet adhesion, activation, and aggregation.
30
What is secondary hemostasis?
Coagulation cascade leading to fibrin clot formation and stabilization
## Footnote
Includes fibrinolysis and tissue regeneration.
31
What initiates the coagulation cascade?
Injury within blood vessels (intrinsic) or injury to tissue around blood vessels (extrinsic)
32
What is the intrinsic pathway of coagulation?
All factors are within the bloodstream and activated by contact factors
## Footnote
Slow but stronger response.
33
What activates the extrinsic pathway of coagulation?
Tissue factor
## Footnote
Provides a rapid response but is less effective in forming a stable clot.
34
What is Vitamin K required for?
Transforming clotting factors II, VII, IX, and X into their functional form
## Footnote
Vitamin K is fat-soluble and also important for bone metabolism.
35
What is the role of von Willebrand factor (vWF) in coagulation?
Acts as a carrier protein for factor VIII and helps anchor the platelet plug.
36
What does aPTT stand for?
Activated Partial Thromboplastin Time
37
True or False: The extrinsic pathway is slower than the intrinsic pathway.
False
## Footnote
The extrinsic pathway is faster but less stable.
38
What is clot retraction?
The process that pulls the edges of the injured endothelium closer together
## Footnote
Activated by thrombin and calcium released by platelets.
39
What can prolonged PT and PTT indicate?
Deficiencies in the common pathway of coagulation
40
What are the stages of coagulation?
* Primary hemostasis
* Secondary hemostasis
* Fibrinolysis
41
What is the function of fibrin stabilizing factor XIIIa?
Stabilizes the fibrin clot
## Footnote
Ensures the clot remains intact.
42
What is the role of calcium (Ca++) in coagulation?
Required at several steps to activate factors
## Footnote
Calcium is often referred to as Factor IV.
43
What is the significance of the clot retraction test?
Assesses platelet function
## Footnote
Not commonly used anymore due to variability in results.
44
What is the time frame for full clotting and retraction in a blood collection tube?
30-60 minutes
## Footnote
Patient on anticoagulants or with low platelet counts may take longer.
45
What is the purpose of collection tubes that contain clot accelerators?
Minimize clotting time
## Footnote
STAT tubes with clot accelerators only require 5 minute clotting.
46
What is the process by which a clot is dissolved called?
Fibrinolysis
47
What happens during clot retraction?
The clot pulls inward releasing serum
48
What is the role of plasminogen in the fibrinolytic system?
It is an inactive enzyme that converts to plasmin when activated
49
What does plasmin do?
Breaks down fibrin strands
50
What is the consequence of no fibrinolysis occurring?
The clot will continue to grow and may result in blockage
51
What are Fibrin degradation products (FDP)?
Products resulting from the breakdown of fibrin
52
What additional factors will plasmin degrade to prevent further clot formation?
* Factors V
* VIII
* II
* XII
53
What are some conditions treated with clot busters?
* Ischemic strokes
* Myocardial Infarction
* Pulmonary embolism
54
Fill in the blank: The enzyme that breaks down the clot is called _______.
Plasmin
55
True or False: Fibrinolysis is a fast-acting process.
False
56
What WBC count in a patient would require further investigation?
200 x10^9/L
## Footnote
A WBC count greater than 200 x10^9/L is indicative of potential underlying pathology.
57
What does the presence of schistocytes in acute promyelocytic leukemia suggest?
DIC (Disseminated Intravascular Coagulation)
## Footnote
Schistocytes are fragmented red blood cells often seen in conditions associated with DIC.
58
What is the most valuable test for a patient with nose bleeds and petechiae following viral infections?
Coag studies, retic, flow cytometry
## Footnote
These tests help assess platelet function and the underlying cause of thrombocytopenia.
59
What does a strong diffuse PAS reaction in blood films indicate?
Presence of proerythroblasts and homogenous positivity in later normoblasts
## Footnote
This reaction is associated with certain hematological conditions, including acute leukemias.
60
What is Immune Thrombocytopenia (ITP)?
Autoantibodies against platelets
## Footnote
ITP can be classified as acute or chronic, with different clinical implications.
61
What is the most common cause of thrombocytosis?
Myeloproliferative disorders
## Footnote
Essential thrombocythemia is the most frequent cause of elevated platelet counts.
62
What does Glanzmann Thrombasthenia result from?
Deficiency or defect of GpIIb/IIIa
## Footnote
This condition leads to impaired platelet aggregation and increased bleeding risk.
63
What is von Willebrand Disease (vWD) primarily associated with?
Defects in platelet adhesion and aggregation
## Footnote
vWD is the most common inherited bleeding disorder, affecting both men and women equally.
64
What factors can affect vWF levels?
Pregnancy, stress, exercise, infections
65
What is the bleeding time result in patients with vWD?
Prolonged
66
What does PTT assess in relation to vWD?
Coagulation pathway that includes FVIII
67
Does the VWF Antigen test indicate how well the VWF functions?
No
68
What is the result of a low vWF level on Factor VIII levels in vWD?
Can cause a low Factor VIII level
69
What does Ristocetin (vWF:Rco) test measure?
Aggregation of platelets in the presence of Ristocetin
70
What is Desmopressin used for in vWD treatment?
To increase release of endothelial vWF
71
What is given to nonresponsive patients with vWD?
Factor replacement therapy
72
What can Cryoprecipitate/FFP be given for in vWD?
To replace missing vWF
73
Name two syndromes associated with vWD.
* Gp Ib Bernard Soulier
* Glanzmann’s IIb/IIIa
74
What are the key stages of hemostasis?
1. Vascular spasm
2. Platelet plug formation
3. Coagulation
4. Clot retraction and repair
5. Fibrinolysis
## Footnote
Hemostasis is the process of preventing or stopping bleeding by clot formation.
75
What is the definition of hemostasis?
The process of preventing or stopping bleeding by clot formation
## Footnote
'Hemo' means blood, and 'stasis' means stop or cease.
76
What happens during platelet activation?
Platelets are activated to their dendrite form and release chemical mediators
## Footnote
Degranulation occurs, releasing serotonin, ADP, and thromboxane.
77
What is the stable clot composed of?
Platelet plug + fibrin produced by the coagulation cascade + trapped RBCs and WBCs
## Footnote
The stable clot is also known as the red platelet plug.
78
What is the normal platelet count range?
150-400 x 10^9/L
## Footnote
Counts below 150 x 10^9/L indicate thrombocytopenia.
79
What is thrombocytopenia?
Platelet count <150 x 10^9/L
## Footnote
It is the single most common cause of bleeding.
80
What is the critical platelet count value?
< 10 x 10^9/L
## Footnote
This count is considered high risk for a hemorrhagic episode.
81
What is the most common cause of increased bleeding time?
Aspirin
## Footnote
Aspirin irreversibly blocks platelet activation and aggregation.
82
What is the function of thromboxane?
Stimulates platelet aggregation and contributes to vasoconstriction
## Footnote
Thromboxane is released during platelet activation.
83
What is the role of thrombopoietin (TPO)?
Stimulates platelet production in bone marrow
## Footnote
TPO is produced primarily by parenchymal cells in the liver.
84
What is the platelet morphology typically observed in chronic ITP?
Normal except larger in size (increased MPV)
85
How can ITP be classified?
* Primary - Usually idiopathic
* Secondary - Due to autoimmune disorders, infections, or severe bacterial infections
86
What distinguishes heparin-induced thrombocytopenia (HIT) Type I from Type II?
* Type I - Usually mild and transient
* Type II - Can be very severe
87
What is a significant risk factor associated with immune drug-induced thrombocytopenia?
Severe bleeding with platelet counts sometimes < 10 x10^9/L
88
What is the treatment protocol upon diagnosis of heparin-induced thrombocytopenia?
Remove heparin therapy immediately
89
What is the risk associated with splenectomy in thrombocytopenia patients?
Can lead to thrombosis due to a platelet rush immediately after removal
90
What laboratory findings are typically seen in TTP/HUS/HELLP?
* Markedly decreased platelet count
* Normal PT, APTT, fibrinogen, FDP-D-dimer tests
