A 58-year-old man with a history of poorly controlled hypertension is brought to the emergency department by his wife. She reports that he has been complaining of a progressively worsening headache over the past 2 days. Today, she found him confused, drowsy, and complaining of blurred vision. He has a history of hypertension for 10 years for which he was prescribed lisinopril, but he admits to taking it only sporadically. He denies any chest pain, shortness of breath, recent trauma, fever, or illicit drug use. He consumes alcohol occasionally. His initial laboratory studies, drawn on arrival, are pending.