4) A 36-year-old woman presents with a one-day history of fever, headache, and lethargy. She developed myalgia, lethargy, mild headache, and cough the previous day and became febrile to 39.1°C. She decided to seek medical care after she started experiencing nausea, vomiting, and presyncopal symptoms while urinating. She has a history of Hashimoto thyroiditis and primary adrenal insufficiency. She takes levothyroxine 125 µg daily, hydrocortisone 15 mg in the morning and 10 mg in the afternoon, and fludrocortisone 0.05 mg once daily. Her blood pressure is 88/50 mm Hg, her heart rate is 104 beats per minute, and her temperature is 38.5°C. She has an oxygen saturation of 99% while breathing ambient air. Physical examination is notable for regular tachycardia but is otherwise unremarkable. In addition to intravenous normal saline, which one of the following agents is the best means of initially managing this patient's hypotension?
