Pre-operative investigation recommended before surgical procedures in a patient on warfarin therapy is
**Core Concept**
Warfarin is a vitamin K antagonist that inhibits the synthesis of vitamin K-dependent clotting factors (II, VII, IX, X) in the liver. This leads to a decrease in the production of these clotting factors, increasing the risk of bleeding. Pre-operative investigations are essential to assess the patient's bleeding risk and adjust the anticoagulant therapy accordingly.
**Why the Correct Answer is Right**
The recommended pre-operative investigation in a patient on warfarin therapy is a coagulation profile, specifically the International Normalized Ratio (INR). The INR measures the activity of the extrinsic and common coagulation pathways and is used to monitor the effectiveness of warfarin therapy. An elevated INR indicates a prolonged prothrombin time and an increased risk of bleeding. The INR is a crucial parameter in assessing the bleeding risk and guiding the perioperative management of patients on warfarin.
**Why Each Wrong Option is Incorrect**
**Option A:** Platelet count is not a relevant investigation in this context, as warfarin affects the production of clotting factors, not platelet function.
**Option B:** Bleeding time is not a sensitive test for assessing the bleeding risk in patients on warfarin therapy.
**Option C:** Fibrinogen levels are not directly affected by warfarin therapy, making this investigation less relevant.
**Clinical Pearl / High-Yield Fact**
Patients on warfarin therapy require careful perioperative management to minimize the risk of bleeding. A thorough review of the patient's medication list, including warfarin, is essential to identify potential bleeding risks and optimize anticoagulant therapy.
**Correct Answer: D. INR measurement**