A nurse is caring for a client who is receiving argatroban IV for HIT and requires urgent surgery. The nurse should stop the infusion at least how many hours before the surgery?

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

This is because argatroban is a direct thrombin inhibitor that can be used as an alternative anticoagulant for patients with heparin-induced thrombocytopenia (HIT).HIT is an immune-mediated disorder that occurs when antibodies form against heparin and platelet factor 4, leading to platelet activation and thrombosis.The diagnosis of HIT is based on clinical criteria and laboratory tests.

Choice A is wrong because warfarin is a vitamin K antagonist that interferes with the synthesis of clotting factors II, VII, IX, and X.Warfarin is contraindicated in patients with HIT because it can worsen the thrombotic complications and cause skin necrosis.Warfarin should only be started after the platelet count has recovered and the patient is adequately anticoagulated with a non-heparin agent.

Choice B is wrong because clopidogrel is an antiplatelet agent that inhibits the ADP receptor on platelets, preventing their aggregation.Clopidogrel is not effective for the treatment of HIT, as it does not target the underlying mechanism of thrombin generation.Clopidogrel may also increase the risk of bleeding in patients with HIT.

Choice D is wrong because alteplase is a fibrinolytic agent that converts plasminogen to plasmin, which breaks down fibrin clots.Alteplase is not indicated for the treatment of HIT, as it does not prevent further thrombosis and may cause severe bleeding complications.Alteplase may be used as a last resort for life-threatening thrombosis in patients with HIT who do not respond to other therapies.