CCS Hemostasis and Coagulation Management 3 — Questions and Answers
Question 1: In the coagulation cascade, which pathway is initiated by tissue factor exposure at the site of vascular injury?
- Intrinsic pathway
- Extrinsic pathway (Correct answer)
- Common pathway
- Fibrinolytic pathway
Correct answer: Extrinsic pathway
The extrinsic pathway is triggered when tissue factor (TF), exposed after vascular injury, binds circulating factor VIIa to initiate coagulation.
Question 2: Which topical hemostatic agent works by providing a physical matrix that activates the intrinsic coagulation pathway and is derived from bovine or human thrombin?
- Gelatin foam (Gelfoam)
- Oxidized cellulose (Surgicel)
- Fibrin sealant (Tisseel) (Correct answer)
- Bone wax
Correct answer: Fibrin sealant (Tisseel)
Fibrin sealants contain concentrated fibrinogen and thrombin; when applied, they mimic the final common pathway of coagulation, rapidly forming a fibrin clot at the bleeding site.
Question 3: Which point-of-care viscoelastic test provides information about clot formation, clot strength, and fibrinolysis and is commonly used to guide transfusion in cardiac surgery?
- Bleeding time
- Activated clotting time (ACT)
- Thromboelastography (TEG) or ROTEM (Correct answer)
- Platelet aggregation assay
Correct answer: Thromboelastography (TEG) or ROTEM
TEG (thromboelastography) and ROTEM (rotational thromboelastometry) are viscoelastic tests that assess whole-blood clotting dynamics, including clot initiation, propagation, strength, and fibrinolysis.
Question 4: Which coagulation factor is activated by thrombin and serves as the final enzyme in converting fibrinogen to fibrin?
- Factor Xa
- Thrombin (Factor IIa) (Correct answer)
- Factor XIIIa
- Factor VIIa
Correct answer: Thrombin (Factor IIa)
Thrombin (Factor IIa) cleaves fibrinogen into fibrin monomers that polymerize to form a fibrin clot, and also activates Factor XIII to cross-link and stabilize the clot.
Question 5: A patient with known heparin-induced thrombocytopenia (HIT) requires cardiac surgery with CPB. Which anticoagulant is the preferred alternative to heparin?
- Low molecular weight heparin (LMWH)
- Fondaparinux
- Bivalirudin (Correct answer)
- Argatroban
Correct answer: Bivalirudin
Bivalirudin is the preferred alternative anticoagulant for CPB in HIT patients; it directly inhibits thrombin, has a short half-life, and can be monitored by ACT.
Question 6: During cardiac surgery, epsilon-aminocaproic acid (EACA) reduces bleeding by which mechanism?
- Inhibiting platelet aggregation
- Binding and inactivating heparin
- Competitively inhibiting plasminogen binding to fibrin (Correct answer)
- Activating thrombin generation
Correct answer: Competitively inhibiting plasminogen binding to fibrin
EACA competitively inhibits the binding of plasminogen (and plasmin) to fibrin, thereby preventing fibrinolysis and preserving clot integrity.
Question 7: Which fibrinogen level is generally considered the threshold below which fibrinogen replacement (cryoprecipitate or fibrinogen concentrate) should be considered in a bleeding cardiac surgery patient?
- Below 400 mg/dL
- Below 200 mg/dL (Correct answer)
- Below 100 mg/dL
- Below 50 mg/dL
Correct answer: Below 200 mg/dL
A fibrinogen level below 200 mg/dL is the generally accepted threshold for replacement therapy in surgical patients with active bleeding, as adequate fibrinogen is essential for clot formation.
CCS Hemostasis and Coagulation Management 3
In the coagulation cascade, which pathway is initiated by tissue factor exposure at the site of vascular injury?