CVP Coagulation and Anticoagulation Management 2 — Questions and Answers
Question 1: Which antifibrinolytic agent acts as a broad serine protease inhibitor, directly inhibiting plasmin, kallikrein, and thrombin?
- Tranexamic acid
- Epsilon-aminocaproic acid (EACA)
- Aprotinin (Correct answer)
- Desmopressin (DDAVP)
Correct answer: Aprotinin
Aprotinin is a naturally derived serine protease inhibitor that directly inhibits plasmin, kallikrein, and thrombin, providing broad antifibrinolytic and anti-inflammatory effects during CPB.
Question 2: On a TEG (thromboelastography) tracing, the Maximum Amplitude (MA) primarily reflects:
- Thrombin generation speed
- Platelet function and platelet-fibrin clot strength (Correct answer)
- Fibrinolytic activity rate
- Coagulation factor concentration
Correct answer: Platelet function and platelet-fibrin clot strength
MA represents the maximum clot strength on TEG and is primarily determined by platelet function (~80%) and fibrin cross-linking (~20%), reflecting overall clot integrity.
Question 3: A post-CPB patient has persistent microvascular bleeding with markedly reduced fibrinogen on ROTEM. The most appropriate blood product is:
- Fresh Frozen Plasma (FFP)
- Platelets
- Cryoprecipitate (Correct answer)
- Packed Red Blood Cells (pRBCs)
Correct answer: Cryoprecipitate
Cryoprecipitate contains the highest concentration of fibrinogen, Factor VIII, vWF, and Factor XIII per unit volume, making it the preferred treatment for hypofibrinogenemia-related coagulopathy.
Question 4: Tranexamic acid reduces surgical blood loss primarily by:
- Inhibiting thrombin generation via the intrinsic pathway
- Competitively blocking lysine-binding sites on plasminogen (Correct answer)
- Increasing platelet aggregation via ADP receptors
- Activating Factor XIII cross-linking
Correct answer: Competitively blocking lysine-binding sites on plasminogen
Tranexamic acid is a synthetic lysine analogue that blocks the lysine-binding sites on plasminogen, preventing its binding to fibrin and subsequent activation to plasmin, thereby inhibiting fibrinolysis.
Question 5: Which coagulation factor is most significantly reduced by hemodilution and consumption during cardiopulmonary bypass?
- Factor I (Fibrinogen) (Correct answer)
- Factor V
- Factor VIII
- Factor XII
Correct answer: Factor I (Fibrinogen)
Fibrinogen (Factor I) is the most significantly reduced coagulation protein during CPB due to hemodilution, consumption by the coagulation cascade, and fibrinolysis.
Question 6: The intrinsic coagulation pathway is initiated by:
- Tissue factor binding to Factor VIIa
- Contact activation of Factor XII on negatively charged surfaces (Correct answer)
- Thrombin-mediated positive feedback on Factor V
- Collagen-induced platelet activation releasing ADP
Correct answer: Contact activation of Factor XII on negatively charged surfaces
The intrinsic pathway begins with activation of Factor XII (Hageman factor) upon contact with negatively charged surfaces such as exposed subendothelium or foreign materials like CPB tubing.
Question 7: In a patient with known HIT antibodies requiring urgent cardiac surgery, which anticoagulant is most appropriate for CPB?
- Low molecular weight heparin (LMWH)
- Unfractionated heparin at double the standard dose
- Bivalirudin (a direct thrombin inhibitor) (Correct answer)
- Fondaparinux
Correct answer: Bivalirudin (a direct thrombin inhibitor)
Bivalirudin is the preferred alternative anticoagulant for CPB in HIT patients because it is a direct thrombin inhibitor that does not interact with PF4 antibodies and has a short half-life.
CVP Coagulation and Anticoagulation Management 2
Which antifibrinolytic agent acts as a broad serine protease inhibitor, directly inhibiting plasmin, kallikrein, and thrombin?