Review Question - QID 213547

A 70-year-old man with a history of Alzheimer dementia presents to the emergency department with a change in his behavior. The patient has been more confused recently and had a fever. Upon presentation, he is too confused to answer questions. His temperature is 103°F (39.4°C), blood pressure is 102/68 mmHg, pulse is 157/min, respirations are 22/min, and oxygen saturation is 99% on room air. The patient is given 3 liters of IV fluids and acetaminophen and his vitals improve. He is also less confused. The patient is asking where he is and becomes combative and strikes a nurse when he finds out he has to be admitted to the hospital. He is given sedation and put in soft restraints. His mental status subsequently worsens and he becomes much more aggressive, spitting at nurses and attempting to bite his restraints. He also complains of abdominal pain. A post void residual volume is notable for a urine volume of 750 mL. Which of the following is the etiology of this patient’s recent mental status change?