Final answer:
The nurse would monitor the International Normalized Ratio (INR) to determine a therapeutic response to warfarin.
Step-by-step explanation:
The nurse would monitor the International Normalized Ratio (INR) to determine a therapeutic response to warfarin. INR is a lab test that measures the speed of a specific pathway of coagulation and compares it to normal. A higher INR indicates a longer time for blood to clot, which is the desired therapeutic effect of warfarin.