Heparin therapy should be monitored with intermittent estimation of-
## **Core Concept**
Heparin is an anticoagulant medication used to prevent and treat thrombotic disorders. Its mechanism of action involves enhancing the activity of antithrombin III, which inhibits thrombin and other clotting factors. Monitoring of heparin therapy is crucial to prevent bleeding complications and ensure its efficacy.
## **Why the Correct Answer is Right**
The correct answer, **Activated Partial Thromboplastin Time (aPTT)**, is the test used to monitor heparin therapy. Heparin primarily affects the intrinsic and common pathways of coagulation, which are reflected in the aPTT. This test measures the time it takes for blood to clot by the intrinsic pathway and is sensitive to the effects of heparin. The therapeutic range for heparin is usually considered to be 1.5 to 2.5 times the control value.
## **Why Each Wrong Option is Incorrect**
- **Option A: Prothrombin Time (PT)**. This test is primarily used to monitor warfarin therapy, not heparin. Warfarin affects the extrinsic and common pathways of coagulation.
- **Option B: International Normalized Ratio (INR)**. Like PT, INR is used to monitor warfarin therapy. INR is a standardized measure that allows for comparison of PT results across different laboratories.
- **Option D: Platelet count**. While heparin-induced thrombocytopenia (HIT) is a potential side effect of heparin therapy, monitoring platelet count is not the primary method for adjusting heparin dose.
## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that the **aPTT** is the primary test used to monitor the effectiveness and safety of heparin therapy. Heparin therapy should be adjusted to maintain an aPTT within the therapeutic range to minimize the risk of thrombosis and bleeding.
## **Correct Answer:** . **Activated Partial Thromboplastin Time (aPTT)**