## **Core Concept**
The question tests the understanding of warfarin-induced bleeding management, specifically the role of fresh frozen plasma (FFP) in reversing anticoagulation. Warfarin acts by inhibiting vitamin K-dependent clotting factors, and its effect is monitored by the prothrombin time (PT) and international normalized ratio (INR). In cases of major bleeding, rapid reversal of anticoagulation is crucial.

## **Why the Correct Answer is Right**
To determine the amount of FFP required, we consider that 1 unit of FFP is expected to increase the recipient's factor levels by approximately 20-30%. A commonly used formula to guide FFP administration in this context is:
[ text{Volume of FFP (mL) to be administered} = frac{text{Desired change in INR} times text{Patient's weight (kg)} times 0.6}{text{Pre-transfusion factor level (IU/mL)}} ]
However, for simplicity and urgency in clinical practice, a frequently used guideline is to administer 1-2 units (approximately 200-400 mL) of FFP for mild to moderate elevations in INR and 2-4 units (approximately 400-800 mL) for more significant elevations. Given the patient's INR of 1.5, which is mildly elevated (therapeutic range for many indications is 2.0-3.0), and assuming a goal INR of approximately 1, a decrease of 0.5 is desired.
The correct answer, **B. 2 units**, seems reasonable for mildly elevated INR levels, aiming for a more rapid correction without overcorrection.

## **Why Each Wrong Option is Incorrect**
- **Option A:** is incorrect because 1 unit might not be sufficient to adequately decrease the INR from 1.5 to near-normal levels, especially in a situation requiring prompt correction.
- **Option C:** and **Option D:** are incorrect because 4 units or more might be excessive for correcting a mildly elevated INR of 1.5, potentially leading to volume overload or other complications.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the goal of FFP administration in warfarin reversal is not necessarily to normalize the INR completely but to bring it into a safe range that minimizes bleeding risk while avoiding thrombotic complications. The dose of FFP should be titrated to effect, and in some cases, additional interventions like vitamin K administration may also be necessary.

## **Correct Answer:** .