A male client with atrial fibrillation who is receiving maintenance rapy of warfarin (Coumadin) has a prothrombin time of 37 seconds. Based on result, nurse will follow which of following doctor’s orders?

Correct Answer: D. Withholding the next dose of warfarin.

The normal prothrombin time is 9.6 to 11.8 seconds (male adult). A therapeutic level PT level is 1.5 to 2 times higher than the normal level. Since the value of 37 seconds is high, the nurse should expect that the client’s next dose of warfarin will be withheld. Patients receiving treatment with warfarin should have close monitoring to ensure the safety and efficacy of the medication. Periodic blood testing is recommended to assess the patient’s prothrombin time (PT) and the international normalized ratio (INR).

• Option A: The laboratory parameter utilized to monitor warfarin therapy is the PT/INR. The PT is the number of seconds it takes the blood to clot, and the INR allows for the standardization of the PT measurement depending on the thromboplastin reagent used by a laboratory. Therefore, monitoring a patient’s INR while on warfarin is strongly preferable over PT because it allows for a standardized measurement without variations due to different laboratory sites.
• Option B: Routine assessment of INR is essential in the management of patients receiving warfarin therapy. The INR of a patient who is not on anticoagulation therapy is approximately 1.0. If a patient has an INR of 2.0 or 3.0, that would indicate that it takes two or three times longer for that individual’s blood to clot than someone who does not take any anticoagulants.
• Option C: The therapeutic INR goal for patients on warfarin therapy is dependent on the indication but may vary based on the patient’s clinical presentation and provider preference. Most patients on warfarin have an INR goal of 2 to 3. However, specific indications, such as a mechanical mitral valve, require an INR goal of 2.5 to 3.5.