CVP Coagulation and Anticoagulation Management 1 — 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.
CVP Coagulation and Anticoagulation Management 1
What is the minimum Activated Clotting Time (ACT) required before initiating cardiopulmonary bypass?