A nurse is caring for a patient who is receiving heparin therapy via continuous IV infusion for treatment of deep vein thrombosis (DVT). The nurse should monitor which of the following laboratory values to evaluate therapeutic effectiveness of heparin therapy?

The correct answer is choice A) Activated partial thromboplastin time (aPTT). This is because aPTT is the most commonly used laboratory test to monitor the therapeutic effect of heparin therapy.

Heparin is an anticoagulant that inhibits the formation of thrombin and fibrin, which are essential for blood clotting. Heparin therapy is indicated for the treatment of deep vein thrombosis (DVT), which is a condition where blood clots form in the deep veins of the legs or pelvis.

Choice B) Prothrombin time (PT) is wrong because PT is used to monitor the therapeutic effect of warfarin therapy, not heparin therapy.

Warfarin is another anticoagulant that inhibits the synthesis of vitamin K-dependent clotting factors. Warfarin therapy is also indicated for the treatment of DVT, but it has a different mechanism of action and monitoring than heparin therapy.

Choice C) International normalized ratio (INR) is wrong because INR is a standardized way of reporting PT results that accounts for the variability of different laboratory methods. INR is also used to monitor the therapeutic effect of warfarin therapy, not heparin therapy.

Choice D) Platelet count is wrong because platelet count is not directly affected by heparin therapy. However, platelet count should be monitored periodically in patients receiving heparin therapy to detect heparin-induced thrombocytopenia (HIT), which is a rare but serious complication of heparin therapy that causes a drop in platelet count and an increased risk of thrombosis.

Choice E) Hemoglobin is wrong because hemoglobin is not directly affected by heparin therapy. However, hemoglobin should be monitored periodically in patients receiving heparin therapy to detect bleeding complications, which are the most common adverse effects of heparin therapy.

The normal range for aPTT is 25 to 35 seconds, but the therapeutic range for heparin therapy is usually 1.5 to 2.5 times the normal range, depending on the indication and protocol.

The normal range for PT is 11 to 13 seconds, and the therapeutic range for warfarin therapy is usually an INR of 2 to 3, depending on the indication and protocol