A patient receiving heparin therapy develops a platelet count of 120,000/mm3 (normal: 150,000-450,000) and presents with red and swollen legs. The nurse suspects Heparin-Induced thrombocytopenia. What is the nurse's priority action?

Continue heparin therapy and monitor platelet counts.

Discontinue heparin immediately and start an alternative anticoagulant,

Administer platelet transfusion to manage thrombocytopenia.

Administer intravenous fluids to prevent dehydration.