Measuring and treating abnormal coagulation

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Questions and Answers

What is the purpose of collecting blood samples into citrate for coagulation tests?

To introduce thromboplastin into the sample.
To chelate calcium and prevent clotting. (correct)
To activate the clotting cascade.
To accelerate fibrin clot formation.

In the Prothrombin Time (PT) assay, which substance is used to initiate coagulation?

Tissue Factor (Thromboplastin) (correct)
Kaolin
Calcium alone
Silica

What is the primary importance of using an appropriate reference plasma in coagulation assays like PT and APTT?

To ensure the presence of excess calcium.
To maintain consistent levels of coagulation factors and minimize variability. (correct)
To accelerate the formation of the fibrin clot.
To provide a standardized source of phospholipids.

Which coagulation pathway is primarily assessed by the Prothrombin Time (PT) assay?

Extrinsic Pathway (D) Signup and view all the answers

What is the initiating agent for coagulation in the Activated Partial Thromboplastin Time (APTT) assay?

Kaolin or Silica (A) Signup and view all the answers

Which coagulation pathway is primarily assessed by the Activated Partial Thromboplastin Time (APTT) assay?

Intrinsic Pathway (C) Signup and view all the answers

What is the direct product of prothrombin activation?

Thrombin (D) Signup and view all the answers

What is the role of thrombin in the coagulation cascade?

Converting fibrinogen to fibrin (C) Signup and view all the answers

What is the final product of the coagulation cascade?

Fibrin clot (B) Signup and view all the answers

Which of the following factors is part of the extrinsic pathway?

Factor VII (C) Signup and view all the answers

In the context of coagulation testing, what does the term 'laboratory assessment of coagulation' generally refer to?

Quantifying coagulation factors and measuring the time it takes for blood to clot. (B) Signup and view all the answers

What is the role of phospholipids (PL) in the coagulation cascade?

To provide a surface for the assembly of coagulation factor complexes. (B) Signup and view all the answers

What is the role of Vitamin K in the coagulation cascade?

It is required for the carboxylation of certain coagulation factors, enabling them to bind calcium. (B) Signup and view all the answers

Which contact activator is converted into Kallikrein?

Prekallikrein (C) Signup and view all the answers

What is the critical role of Calcium ($Ca^{2+}$) in both the intrinsic and extrinsic pathways of coagulation?

It acts as a cofactor, facilitating the binding of coagulation factors to phospholipid surfaces. (B) Signup and view all the answers

How does Warfarin (Coumadin) affect the coagulation cascade?

By blocking the synthesis of vitamin K-dependent clotting factors. (A) Signup and view all the answers

What laboratory result would you expect in a patient with a Factor VIII deficiency?

Prolonged APTT (B) Signup and view all the answers

What is the effect of heparin on coagulation?

Enhances the activity of antithrombin (A) Signup and view all the answers

What is the role of TT (Thrombin Time) in the coagulation cascade?

Laboratory test of thrombin in converting fibrinogen to fibrin (C) Signup and view all the answers

What is the mechanism of action of Warfarin?

Competitively inhibiting vitamin K, which affects the gamma-carboxylation of coagulation factors. (B) Signup and view all the answers

Which coagulation factors are affected by Warfarin's mechanism of action?

Factors VII, IX, X, prothrombin, and protein C. (B) Signup and view all the answers

What is a common clinical application of Warfarin?

Prevention of deep vein thrombosis (DVT) and pulmonary embolism. (B) Signup and view all the answers

How does Heparin exert its anticoagulant effect?

By increasing the activity of antithrombin and reducing Factor Xa and thrombin activity. (C) Signup and view all the answers

In which clinical scenario is Heparin commonly used as an anticoagulant?

Anticoagulation following orthopedic surgery. (A) Signup and view all the answers

What is the mechanism of action of Aspirin in preventing thrombotic events?

It irreversibly inhibits cyclooxygenase (COX), which is essential for the formation of thromboxane $A_2$ ($TXA_2$). (D) Signup and view all the answers

What is the primary target of Warfarin that leads to its therapeutic effect?

Interference with Vitamin K-dependent gamma-carboxylation. (B) Signup and view all the answers

Which of the following best describes the route of administration for Heparin?

Subcutaneous or intravenous injection. (A) Signup and view all the answers

What is the key enzyme inhibited by Aspirin to reduce the risk of thrombotic events?

Cyclooxygenase (COX). (C) Signup and view all the answers

Which of the following medications would be most appropriate for the immediate anticoagulation needs of a patient undergoing emergency surgery?

Heparin. (C) Signup and view all the answers

What is the primary reason Warfarin is used in the treatment of stroke?

To prevent the formation of new clots in patients at risk (C) Signup and view all the answers

A patient is prescribed Warfarin. What dietary advice is most crucial to provide?

Maintain a consistent intake of vitamin K-rich foods to avoid fluctuations in INR levels. (B) Signup and view all the answers

Why is Aspirin often recommended in low doses for individuals at high risk of cardiovascular events?

To prevent platelet aggregation and reduce the risk of clot formation. (A) Signup and view all the answers

A patient with a history of orthopedic surgery is prescribed Heparin. What is the primary reason for this prescription?

To decrease the risk of blood clot formation during recovery. (A) Signup and view all the answers

If a patient on Warfarin requires an emergency surgery, what intervention is typically necessary to manage their anticoagulation?

Administer Vitamin K to reverse the effects of Warfarin. (C) Signup and view all the answers

How does Warfarin treatment prevent pulmonary embolism?

By preventing the formation of new blood clots that could travel to the lungs. (B) Signup and view all the answers

What is the most probable reason that Heparin is favored over Warfarin in certain clinical situations requiring anticoagulation?

Heparin acts quicker than Warfarin. (B) Signup and view all the answers

Why is the inhibition of cyclooxygenase (COX) by Aspirin considered irreversible?

Aspirin permanently modifies the COX enzyme. (A) Signup and view all the answers

Which of the following is a primary target of Heparin, leading to the inhibition of coagulation?

Factor Xa (A) Signup and view all the answers

A patient on Warfarin has an elevated INR. Which of the following actions should be taken?

Administer Vitamin K (A) Signup and view all the answers

Flashcards

PT (Prothrombin Time)

A test that measures the integrity of the extrinsic pathway of coagulation. Initiated by adding thromboplastin, calcium, and time to formation of fibrin clot.

APTT (Activated Partial Thromboplastin Time)

A test that measures the integrity of the intrinsic pathway of coagulation. Initiated by adding kaolin or silica, calcium, and time to formation of fibrin clot.

Why blood is collected in citrate?

Blood is collected into citrate to chelate calcium and prevent clotting.

Reference plasma use

To ensure accurate results, it's important to use an appropriate reference plasma and source of TF (thromboplastin) from the same species.