CVP Coagulation and Anticoagulation Management — Questions and Answers

Question 1: What is the minimum Activated Clotting Time (ACT) required before initiating cardiopulmonary bypass?

200 seconds
300 seconds
400 seconds (Correct answer)
480 seconds

Correct answer: 400 seconds

An ACT of 400 seconds or greater is required before initiating CPB to ensure adequate anticoagulation and prevent clot formation within the extracorporeal circuit.

Question 2: What is the standard initial heparin dose administered before cardiopulmonary bypass?

100 units/kg
200 units/kg
300 units/kg (Correct answer)
400 units/kg

Correct answer: 300 units/kg

The standard initial heparin dose for CPB is 300 units/kg, which typically achieves a target ACT greater than 400 seconds prior to bypass.

Question 3: Heparin exerts its anticoagulant effect primarily by potentiating which plasma protein?

Protein C
Antithrombin III (Correct answer)
Alpha-2 macroglobulin
Thrombomodulin

Correct answer: Antithrombin III

Heparin binds to antithrombin III and dramatically accelerates its inhibition of thrombin (Factor IIa) and Factor Xa, preventing fibrin formation.

Question 4: What is the standard protamine-to-heparin ratio used to reverse anticoagulation after CPB?

0.5 mg protamine per 100 units heparin
1 mg protamine per 100 units heparin (Correct answer)
2 mg protamine per 100 units heparin
3 mg protamine per 100 units heparin

Correct answer: 1 mg protamine per 100 units heparin

The standard reversal ratio is 1 mg protamine per 100 units of heparin administered, titrated based on post-bypass ACT measurements.

Question 5: A patient requires escalating heparin doses to achieve a target ACT before CPB. The most likely cause of heparin resistance is:

Protein C deficiency
Antithrombin III deficiency (Correct answer)
Factor V Leiden mutation
Von Willebrand disease

Correct answer: Antithrombin III deficiency

Heparin resistance is most commonly caused by antithrombin III deficiency, since heparin cannot exert its anticoagulant effect without this cofactor.

Question 6: Which point-of-care test is the standard method for monitoring heparin anticoagulation during cardiopulmonary bypass?

Prothrombin Time (PT)
Activated Partial Thromboplastin Time (aPTT)
Activated Clotting Time (ACT) (Correct answer)
Thromboelastography (TEG)

Correct answer: Activated Clotting Time (ACT)

The ACT is the standard bedside test for monitoring heparin during CPB because it provides rapid results and remains accurate at the high heparin concentrations used for bypass.

Question 7: Heparin-induced thrombocytopenia type II (HIT II) is caused by:

Direct heparin cytotoxicity to megakaryocytes
IgG antibodies against heparin-platelet factor 4 (PF4) complexes (Correct answer)
Complement activation causing platelet lysis
Direct inhibition of thrombopoietin by heparin

Correct answer: IgG antibodies against heparin-platelet factor 4 (PF4) complexes

HIT type II is an immune-mediated disorder in which IgG antibodies form against heparin-PF4 complexes, activating platelets and paradoxically causing thrombosis despite thrombocytopenia.

Question 8: 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 9: 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 10: 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 11: 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 12: 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 13: 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 14: 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.

Question 15: Post-CPB coagulopathy is most commonly caused by:

Vitamin K deficiency from prolonged bypass
Warfarin effect from preoperative medications
Dilutional coagulopathy combined with platelet dysfunction (Correct answer)
Disseminated intravascular coagulation (DIC)

Correct answer: Dilutional coagulopathy combined with platelet dysfunction

Post-CPB coagulopathy is predominantly caused by hemodilution of coagulation factors and platelets combined with acquired platelet dysfunction from contact with CPB circuit surfaces and hypothermia.

Question 16: Desmopressin (DDAVP) is indicated in cardiac surgery primarily to treat bleeding associated with:

Heparin rebound after protamine reversal
Acquired platelet dysfunction including uremic and aspirin-related defects (Correct answer)
Hypofibrinogenemia post-bypass
Antithrombin III deficiency

Correct answer: Acquired platelet dysfunction including uremic and aspirin-related defects

DDAVP stimulates endothelial release of stored von Willebrand factor, enhancing platelet adhesion and aggregation, making it effective for uremic platelet dysfunction and aspirin-induced platelet defects.

Question 17: "Heparin rebound" occurring hours after successful protamine reversal is caused by:

Inadequate protamine dosing leaving residual circulating heparin
Release of tissue-sequestered heparin after protamine is metabolized (Correct answer)
Synthesis of new heparin by mast cells stimulated by surgery
Auto-activation of factor Xa regenerating anticoagulant activity

Correct answer: Release of tissue-sequestered heparin after protamine is metabolized

Heparin rebound occurs when heparin sequestered in tissues or bound to plasma proteins is released into circulation after protamine has been eliminated, causing renewed anticoagulation.

Question 18: Cell salvage (autotransfusion) during cardiac surgery is contraindicated in which of the following situations?

Chronic renal failure with uremic platelet dysfunction
Active bacterial endocarditis with bacteremic surgical field (Correct answer)
Sickle cell trait in a non-crisis patient
Patient age greater than 75 years

Correct answer: Active bacterial endocarditis with bacteremic surgical field

Cell salvage is contraindicated when the surgical field is contaminated with bacteria or malignant cells, as reinfusing this blood can cause bacteremia, sepsis, or tumor dissemination.

Question 19: The most common cause of platelet dysfunction during cardiopulmonary bypass is:

Hypocalcemia from citrated blood products
Contact activation of platelets by the CPB circuit surfaces (Correct answer)
Heparin-mediated direct platelet inhibition
Hypothermia as the sole contributing factor

Correct answer: Contact activation of platelets by the CPB circuit surfaces

Contact between platelets and the foreign surfaces of the CPB circuit causes activation, degranulation, and receptor downregulation, resulting in acquired platelet dysfunction that persists after bypass.

Question 20: Modified ultrafiltration (MUF) performed immediately after CPB provides which primary benefit?

Reversal of residual heparin anticoagulation
Hemoconcentration and removal of inflammatory mediators (Correct answer)
Restoration of platelet count to pre-bypass levels
Correction of electrolyte imbalances only

Correct answer: Hemoconcentration and removal of inflammatory mediators

MUF removes excess crystalloid fluid and inflammatory mediators (cytokines, complement factors) while concentrating red blood cells and coagulation factors, improving hematocrit and reducing post-bypass systemic inflammation.

Question 21: When a post-CPB TEG shows a widened angle (alpha angle) with reduced clot formation rate, the most appropriate intervention is:

Platelet transfusion
Protamine supplementation
Cryoprecipitate or fibrinogen concentrate (Correct answer)
Fresh Frozen Plasma (FFP)

Correct answer: Cryoprecipitate or fibrinogen concentrate

A reduced alpha angle on TEG indicates decreased fibrinogen availability impairing clot propagation; cryoprecipitate or fibrinogen concentrate directly replaces fibrinogen to restore clot formation kinetics.

CVP Coagulation and Anticoagulation Management

What is the minimum Activated Clotting Time (ACT) required before initiating cardiopulmonary bypass?

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