A nurse is caring for a client who has atrial fibrillation and is receiving warfarin therapy to prevent thromboembolism formation. The nurse should monitor which of the following laboratory values to determine the effectiveness of the medication?

Warfarin (Coumadin) is a blood thinner that prevents blood clots from forming or growing larger.

It is used to treat or prevent deep vein thrombosis (DVT), a condition in which a blood clot forms in a vein deep in the body, usually in the legs.

It can also prevent pulmonary embolism (PE), a condition in which a blood clot breaks off and travels to the lungs, blocking blood flow and causing breathing problems.

Patients taking warfarin should follow these instructions:

• Avoid foods that are high in vitamin K.

Vitamin K is needed for the production of some clotting factors in the liver.

Warfarin blocks the action of vitamin K, and thus reduces the clotting ability of the blood.

However, if the intake of vitamin K varies significantly from day to day, it can affect the stability of the warfarin effect.Foods that are high in vitamin K include green leafy vegetables, such as spinach, kale, broccoli, cabbage, and lettuce, as well as some vegetable oils, such as soybean and canola.Patients should not avoid these foods completely, but they should keep their intake consistent and inform their doctor or pharmacist if they make any changes to their diet.

• Report any unusual bleeding to healthcare provider.

Warfarin can increase the risk of bleeding, especially if the dose is too high or if it interacts with other medications or supplements.Patients should notify their doctor or seek emergency care if they have any signs of bleeding, such as bruising, red or black stools, blood in the urine, coughing up blood, vomiting blood, nosebleeds, heavy menstrual bleeding, headaches, dizziness, weakness, or swelling.They should also inform their doctor of any other medications or supplements they are taking, including over-the-counter products and herbal remedies.

• Use an electric razor when shaving.

Warfarin can make the skin more prone to bleeding from minor cuts or injuries.

Patients should use an electric razor when shaving to reduce the risk of nicking themselves and causing bleeding.They should also use a soft toothbrush and avoid flossing if it causes bleeding.They should wear gloves when handling sharp objects or working in the garden.

Choice B and E are wrong because:

• Take aspirin for pain relief.

Aspirin is a medication that also prevents blood clots by inhibiting platelets, which are cells that stick together to form clots.Taking aspirin with warfarin can increase the risk of bleeding significantly and is not recommended unless prescribed by a doctor for a specific reason.Patients should avoid taking aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or naproxen, for pain relief unless advised by their doctor.They should also check the labels of any over-the-counter medications or supplements they use and avoid those that contain aspirin or NSAIDs.

• Wear shoes that fit well and avoid tight clothing.

This instruction is not related to warfarin therapy and does not affect its efficacy or safety.

However, it may be a general advice for patients with DVT to prevent further complications or discomfort.Wearing shoes that fit well and avoiding tight clothing can help improve blood circulation in the legs and prevent swelling or pain.Patients with DVT should also elevate their legs when possible and wear compression stockings if prescribed by their doctor.

The nurse would need to know the patient’s weight and aPTT level before starting the IV continuous Heparin drip.

Here is why:

• Weight: Heparin dosing is based on the patient’s weight, so the nurse would want to make sure the documented weight of the patient is current and accurate.The initial bolus and infusion rate are calculated using the patient’s weight in kilograms.

• aPTT: Heparin works by enhancing the activation of antithrombin III, which prevents the activation of thrombin and the conversion of fibrinogen to fibrin.Heparin affects the intrinsic pathway of clotting, and its therapeutic effect is monitored by measuring the activated partial thromboplastin time (aPTT).The normal range for aPTT is about 30-40 seconds, and the therapeutic range for Heparin is 1.5-2.5 times the normal value.The nurse would need to check the baseline aPTT before starting the drip, and then collect an aPTT level every 6 hours per protocol to adjust the infusion rate as needed.

The other choices are wrong because:

• Vital signs: Although vital signs are important to monitor for any patient, they are not specific to Heparin therapy.Heparin does not affect blood pressure, heart rate, respiratory rate, or temperature directly.

• PT/INR: These are coagulation tests that measure the extrinsic pathway of clotting, which is affected by Vitamin K antagonists such as Warfarin.Heparin does not affect the PT/INR levels, so they are not relevant for Heparin therapy.

• EKG: An electrocardiogram (EKG) is a test that measures the electrical activity of the heart.It can help diagnose cardiac arrhythmias, ischemia, infarction, electrolyte imbalances, and other cardiac conditions.

Heparin does not affect the electrical conduction of the heart, so an EKG is not necessary before starting Heparin therapy