You are assessing a 49-year-old man who complains of chest pressure that began the night before. he is conscious, but anxious, and tells you he has a history of angina and hypertension. after applying high-flow oxygen, you expose his chest to auscultate his lungs and note that he has a nitroglycerin patch on his right upper chest. his skin is cool and pale, his blood pressure is 78/50 mm hg, and his pulse is 110 beats/min and irregular. you should: