A nurse is caring for a patient with an arteriovenous (AV) fistula in the forearm and assesses that a thrill is absent when palpating the venous side of the fistula. What action should the nurse implement?

Send the patient to dialysis for remedy.

Inject the ordered amount of heparin into the fistula.

Report to the charge nurse that the fistula is occluded.

Apply warm compresses and lower the arm below the heart level.