Why is monitoring PT and INR necessary when a patient is on Warfarin?

Monitoring PT (Prothrombin Time) and INR (International Normalized Ratio) is essential for patients on Warfarin due to the drug's role as an anticoagulant. Warfarin works by inhibiting vitamin K-dependent clotting factors, which can significantly affect the coagulation cascade. The primary aim is to maintain the INR within a therapeutic range, indicative of effective anticoagulation without increasing the risk of bleeding.

If a patient's INR is too low, this indicates under-anticoagulation, which increases the risk of thrombotic events, such as strokes or deep vein thrombosis. Conversely, if the INR is too high, the risk of uncontrolled bleeding increases, which can be life-threatening. Therefore, regular monitoring of PT and INR ensures that the patient remains within the desired therapeutic range, thus preventing both under-anticoagulation and over-anticoagulation.

The other concerns listed do not directly relate to the primary purpose of monitoring PT and INR in the context of Warfarin therapy. Effective cardiac output, kidney function, and dehydration management are important considerations in patient care but are not directly tied to the anticoagulation monitoring required for Warfarin therapy.