A 25-year-old woman is brought to the emergency department by her boyfriend because of new-onset confusion. She has been previously healthy and has no significant past medical history. Her temperature is 38.9°C (102°F), pulse is 84/min, respirations are 14/min, and blood pressure is 110/68 mm Hg. Physical examination shows disorientation to time and place, scleral icterus, petechiae in her oral mucosa, face, arms, trunk, and legs. Foley catheter reveals decreased urine output. Laboratory studies show: Erythrocyte count: 3.0 million/mm3 Hemoglobin: 9.0 mg/dL Mean corpuscular volume: 85 μm3 Platelet count: 80,000/mm3 Sodium : 140 mEq/L Potassium: 3.8 mEq/L Total bilirubin: 3.2 mg/dL Direct: bilirubin: 1.0 mg/dL AST: 50 U/L Creatinine: 2.2 mg/dL