A hospitalized patient receiving heparin therapy for DVT (Deep Vein Thrombosis) prophylaxis develops platelet count of 68,000/µL and reports new unilateral calf pain. What is the nurse’s priority action?

The clinical picture described — a drop in platelet count to 68,000/µL during heparin therapy combined with new unilateral calf pain — is highly suspicious for heparin-induced thrombocytopenia type II (HIT). HIT is a prothrombotic, immune-mediated complication in which antibodies form against the heparin-platelet factor 4 complex, causing platelet activation, consumption, and paradoxical thrombosis. The new calf pain represents a possible new venous thrombosis despite anticoagulation. Because continuing heparin in HIT dramatically worsens thrombotic risk and can be life-threatening, the immediate priority action is to stop all heparin products and notify the provider so that an alternative anticoagulant (such as argatroban or fondaparinux) can be ordered. Administering vitamin K reverses warfarin, not heparin, and is therefore inappropriate. Continuing heparin and monitoring ignores the danger of progressive thrombosis and platelet consumption. Applying a warm compress is a comfort measure that does nothing to address the underlying coagulopathy and could dislodge a clot. Prompt heparin discontinuation and provider notification are the cornerstone of HIT management.