A nurse is reviewing the laboratory results of a client who has DVT and is receiving unfractionated heparin IV.

Which of the following laboratory tests should the nurse monitor to evaluate the effectiveness of heparin therapy?

Spinach.The nurse should instruct the client to avoid fluctuations in the amount and frequency of consumption of foods that are rich in vitamin K, such as spinach, because they can make warfarin less effective.Vitamin K is involved in blood clotting and can counteract the anticoagulant effect of warfarin.

Grapefruit is wrong because grapefruit can increase the risk of bleeding by affecting warfarin metabolism or pharmacodynamics.Grapefruit can inhibit the enzyme CYP3A4 that metabolizes warfarin and increase its blood levels.

Cheese is wrong because cheese does not have a significant interaction with warfarin.However, some types of cheese, such as mature cheese and blue cheese, contain small amounts of vitamin K and should be consumed consistently.

Eggs is wrong because eggs do not have a significant interaction with warfarin.However, egg yolks contain some vitamin K and should be consumed consistently.

Activated partial thromboplastin time (aPTT).The aPTT test is used to monitor the effectiveness of heparin therapy in clients with DVT.Heparin works by inhibiting the formation of blood clots by blocking the activity of clotting factors.The aPTT test measures the time it takes for a clot to form in a sample of blood after substances that cause clotting have been added.The normal range for aPTT is 30-40 seconds.

Prothrombin time (PT) is used to monitor warfarin therapy, not heparin therapy.

International normalized ratio (INR) is used to monitor warfarin therapy, not heparin therapy.

D-dimer is used to diagnose DVT, not monitor heparin therapy.