A client receiving unfractionated heparin develops a painful swollen leg. The platelet count has decreased from 220,000/mm3 to 92,000/mm3. Which action should the nurse take first?

A platelet decline of more than half with new thrombosis during heparin exposure strongly suggests heparin-induced thrombocytopenia, a prothrombotic immune reaction. Heparin should be stopped promptly, and the provider should initiate evaluation and a non-heparin anticoagulant when indicated.

Quick answer
Stop heparin and report suspected heparin-induced thrombocytopenia. New thrombosis plus a major platelet decline is a clotting emergency, not a reason to give more heparin.

Why this is correct
In heparin-induced thrombocytopenia, antibodies activate platelets and create thrombosis even as the measured platelet count falls. Continuing heparin sustains the trigger, so stopping exposure and arranging alternative anticoagulation are urgent priorities.

Easy analogy or mental picture
The reaction is like a fire alarm system that accidentally activates machinery that starts more fires. The falling platelet count is visible, but the major danger is thrombosis; the analogy does not replace formal probability scoring and laboratory confirmation.

Memory hook
Heparin plus platelet fall plus new clot means stop heparin and switch the anticoagulation plan.

NCLEX decision rule
When heparin exposure is followed by a substantial platelet decline and thrombosis, treat the pattern as suspected heparin-induced thrombocytopenia. Stop heparin, notify the provider, and expect a non-heparin anticoagulant rather than more heparin, routine platelets, or early warfarin alone.

Why the other choices are wrong
Increasing or continuing heparin worsens the immune trigger. Platelet transfusion is not routine without a separate bleeding indication, and warfarin should not be started while platelets remain markedly decreased in acute HIT.