Coagulation and Anticoagulation Management Flashcards

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

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.

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

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.

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

Answer: Antithrombin III

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

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

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.

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

Answer: Antithrombin III deficiency

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

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

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.

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

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.

Which antifibrinolytic agent acts as a broad serine protease inhibitor, directly inhibiting plasmin, kallikrein, and thrombin?

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.

On a TEG (thromboelastography) tracing, the Maximum Amplitude (MA) primarily reflects:

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.

A post-CPB patient has persistent microvascular bleeding with markedly reduced fibrinogen on ROTEM. The most appropriate blood product is:

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.

Tranexamic acid reduces surgical blood loss primarily by:

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.

Which coagulation factor is most significantly reduced by hemodilution and consumption during cardiopulmonary bypass?

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.

The intrinsic coagulation pathway is initiated by:

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.

In a patient with known HIT antibodies requiring urgent cardiac surgery, which anticoagulant is most appropriate for CPB?

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.

Post-CPB coagulopathy is most commonly caused by:

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.

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

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.

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

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.

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

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.

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

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.

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

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.