A client on postoperative day 6 after hip replacement has received subcutaneous unfractionated heparin for thromboprophylaxis since surgery. The platelet count, 238,000/mm³ on postoperative day 1, is now 92,000/mm³. The client reports new pain in the left foot, which is cool and pale with a diminished Doppler signal. There is no bleeding from the incision or IV sites. PT, fibrinogen, and hemoglobin are within normal limits, the peripheral blood smear shows no schistocytes, and the client is alert and oriented. Complete the diagram by selecting the condition the client is most likely experiencing, 2 actions the nurse should take to address that condition, and 2 parameters the nurse should monitor to assess the client's progress.

Quick answer
Heparin-induced thrombocytopenia with thrombosis; discontinue all heparin including flushes and start the prescribed argatroban; monitor platelet count and aPTT.

Why this is correct
The timing (day 6), the size of the fall (238,000 to 92,000/mm³, a 61% drop), and a new arterial clot fit HIT, and the normal PT, fibrinogen, smear, and mental status argue against DIC and TTP. HIT is prothrombotic, so stopping heparin is not enough; a non-heparin anticoagulant is required. Argatroban is titrated to the aPTT, and a rising platelet count shows the immune process is subsiding.

Easy analogy or mental picture
Heparin has become the spark instead of the fire extinguisher — remove every source of the spark (including flushes) and bring in a different extinguisher (argatroban).

Memory hook
HIT: 4 Ts — Thrombocytopenia, Timing, Thrombosis, no oTher cause. Stop ALL heparin; start a non-heparin agent.

NCLEX decision rule
A platelet drop over 50% 5–10 days after heparin, especially with a new clot, requires stopping all heparin and starting a non-heparin anticoagulant before confirmatory results return.

Why the other choices are wrong
DIC is tempting with low platelets and clotting, but PT and fibrinogen are normal and there is no bleeding, so fibrinogen is not the tracking value. Expected postoperative thrombocytopenia occurs in the first 1–3 days and recovers, not on day 6 with thrombosis. TTP would show schistocytes and often neurologic change, so plasma exchange is not indicated. Enoxaparin cross-reacts with HIT antibodies, and an anti-Xa level monitors heparins. Warfarin started during acute HIT can cause venous limb gangrene and is delayed until platelets recover; INR tracks warfarin, not argatroban.