A 58-yeаr-оld mаle pаtient with angina pectоris is admitted tо the emergency department with chest pain unrelieved by one dose of sublingual nitroglycerin. He reports using Sildenafil (Viagra) for erectile dysfunction earlier in the day. His vital signs are blood pressure 90/56 mm Hg, heart rate 102/min, respiratory rate 22/min, and oxygen saturation 92% on room air. Considering the patient's medication history and current presentation, what is the nurse's priority action?