AI Clotting Lecture Flashcards by Taylor Henderson

What is hemostasis?

Normal hemostasis is a balance between clot generation, thrombus formation, and regulatory mechanisms that inhibit uncontrolled thrombogenesis.

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What are the goals of hemostasis?

To limit blood loss from vascular injury
To maintain intravascular blood flow
To promote revascularization after thrombosis

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What are the two stages of hemostasis?

Primary Hemostasis
Secondary Hemostasis

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What occurs during primary hemostasis?

Immediate platelet deposition at the endovascular injury site, leading to initial platelet plug formation.

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What occurs during secondary hemostasis?

Clotting factors are activated, stabilizing the clot formed and secured with crosslinked fibrin.

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What role do vascular endothelial cells play in hemostasis?

They have antiplatelet, anticoagulant, and fibrolytic effects to inhibit clot formation.

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Name two anti-clotting mechanisms of endothelial cells.

Negatively charged to repel platelets
Produce platelet inhibitors such as prostacyclin and nitric oxide

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What is the lifespan of platelets?

8-12 days.

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What are the three phases of platelet alteration upon endothelial damage?

Adhesion
Activation
Aggregation

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What is the function of alpha granules in platelets?

They contain fibrinogen, factors V & VIII, von Willebrand factor, platelet-derived growth factor, and more.

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What does the term ‘tenase complex’ refer to?

A crucial enzymatic complex in blood coagulation that catalyzes the activation of factor X (FX) to its active form, factor Xa (FXa).

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True or False: The intrinsic pathway plays a major role in the initiation of hemostasis.

False. It plays a minor role and is more of an amplification system.

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What is the prothrombinase complex?

Factor Xa binds with Va to rapidly convert prothrombin (II) into thrombin (IIa).

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What activates the common pathway in coagulation?

Factor Xa initiates the common pathway.

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What is the role of thrombin in coagulation?

Thrombin converts fibrinogen (I) to fibrin (Ia), forming a mesh that stabilizes the clot.

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What are the four major coagulation counter-mechanisms?

Fibrinolysis
Tissue factor pathway inhibitor (TFPI)
Protein C system
Serine Protease Inhibitors (SERPINs)

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What is Von Willebrand’s Disease?

The most common inherited bleeding disorder, characterized by a deficiency in von Willebrand factor, causing defective platelet adhesion/aggregation.

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What are the laboratory findings typically associated with Hemophilia?

Normal PT
Normal platelets
Prolonged PTT

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What is the primary source of coagulation factors in the body?

The liver.

What is traumatic coagulopathy?

Acute coagulopathy seen in trauma patients, often related to activated protein C decreasing thrombin generation.

What is Factor V Leiden mutation?

A mutation that leads to activated protein C resistance, present in 5% of the Caucasian population.

What is Antiphospholipid Syndrome?

An autoimmune disorder characterized by antibodies against phospholipid-binding proteins in the coagulation system, leading to recurrent thrombosis.

Fill in the blank: The most significant cause of intraoperative bleeding is ______.

[anticoagulant medications]

What is the role of DDAVP in von Willebrand’s Disease?

It increases von Willebrand factor levels.

What are common triggers that may precipitate Disseminated Intravascular Coagulation (DIC)?

* Trauma * Amniotic fluid embolus * Malignancy * Sepsis * Incompatible blood transfusion

What greatly increases the risk of thrombosis in certain populations?

Pregnancy, immobility, infection, surgery, and trauma ## Footnote These factors are significant in assessing thrombotic risk.

What is Heparin-Induced Thrombocytopenia (HIT)?

Mild-moderate thrombocytopenia associated with Heparin occurring 5-14 days after treatment ## Footnote Results in platelet count reduction and potential thrombosis.

What is the incidence of autoimmune response in patients receiving heparin?

Up to 5% ## Footnote This response can lead to thrombocytopenia or thrombosis within 1 day of subsequent heparin dose.

Which patients are at higher risk for Heparin-Induced Thrombocytopenia?

Women and patients receiving high heparin doses such as during cardiopulmonary bypass (CPB) ## Footnote These groups are more susceptible to developing HIT.

What should be done if HIT is suspected?

Discontinue heparin and convert to an alternative anticoagulant ## Footnote Warfarin is contraindicated as it decreases protein C and S synthesis.

How is HIT diagnosed?

Confirmed with HIT antibody testing ## Footnote Antibodies are typically cleared from circulation in 3 months.

What does Prothrombin Time (PT) assess?

Integrity of extrinsic and common pathways ## Footnote Reflects deficiencies in factors I, II, V, VII, and X.

What is the normal platelet count?

Greater than 100,000 platelets/microliter ## Footnote This is a standard component of coagulation testing.

What does Activated Partial Thromboplastin Time (aPTT) measure?

Seconds until clot forms after mixing plasma with phospholipid, Ca², and an activator of the intrinsic pathway ## Footnote More sensitive to deficiencies in factors VIII and IX.

What are the three main classes of antiplatelet agents?

* Cyclooxygenase Inhibitors * P2Y12 receptor antagonists * Platelet GIIb/IIIa receptor antagonists ## Footnote Each class has a distinct mechanism of action in inhibiting platelet aggregation.

What is the mechanism of action of Warfarin?

Inhibits synthesis of Vitamin K-dependent factors II, VII, IX, X, Protein C, and S ## Footnote It is commonly used for valvular atrial fibrillation and valve replacements.

What is the reversal agent for Warfarin?

Vitamin K ## Footnote It restores liver carboxylation of vitamin K-dependent factors.

What is the primary mechanism of unfractionated heparin?

Accelerates the activity of antithrombin III, inhibiting thrombin and factor Xa ## Footnote It requires close monitoring and is fully reversible with protamine.

What distinguishes Direct Oral Anticoagulants (DOACs) from traditional anticoagulants?

More predictable pharmacokinetics/dynamics, fewer drug interactions, dosed daily without lab monitoring ## Footnote Efficacy is similar to Warfarin but with shorter half-lives.

What are the two categories of thrombolytics?

* Fibrin-Specific * Non-Fibrin-Specific ## Footnote Fibrin-specific thrombolytics are preferred due to efficacy and safety.

What is the use of antifibrinolytics?

To inhibit fibrinolysis and mitigate blood loss ## Footnote They include lysine analogues and SERPINs.

What are the preoperative guidelines for anticoagulants regarding Warfarin?

Low risk patients should discontinue 5 days prior and restart 12-24 hours postoperative; high risk patients should stop 5 days prior and bridge with UFH or LMWH ## Footnote This ensures safe surgical practices while managing anticoagulation.

What is the recommended waiting period for elective surgery after placement of a bare-metal stent?

6 weeks ## Footnote Drug-eluting stents require a delay of 6 months.

What is the antidote for the DOAC Dabigatran?

Idarucizumab ## Footnote It is used for emergent reversal of the anticoagulant effects of Dabigatran.

What does Activated Clotting Time (ACT) measure?

Variation of whole blood clotting time with an activator ## Footnote It addresses intrinsic and common pathways and is used to measure responsiveness to heparin.