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

Heparin works faster than warfarin, so it is given until warfarin reaches an effective level in your blood.

Heparin has a shorter duration of action than warfarin, so it is easier to reverse if bleeding occurs.

Choice B is wrong because heparin and warfarin do not have a synergistic effect.

They work on different clotting factors, but they do not enhance each other’s effects.

Choice C is wrong because the route of administration is not relevant to the rationale for using both medications.

Heparin and warfarin can be given by different routes, but that does not explain why they are both necessary.

Choice D is wrong because warfarin does not help dissolve existing clots.

Warfarin prevents the synthesis of vitamin K-dependent clotting factors, but it does not break down clots that have already formed.