Psychiatrymiddle twist
An 84-year-old woman with metastatic breast cancer is admitted from her retirement village because over four days she has become drowsy by day, restless at night and unable to follow a conversation. She is afebrile, rousable but inattentive, and has no focal neurological sign. Sodium 129 mmol/L (135 to 145), corrected calcium 3.38 mmol/L (2.10 to 2.60), urea 9.6 mmol/L (3.0 to 8.0), creatinine 116 micromol/L (45 to 90), thyroid-stimulating hormone 6.9 milli-int.unit/L (0.4 to 4.0), C-reactive protein 4 mg/L (less than 5). Urine dipstick shows leucocytes but no nitrites. Which one of the following best accounts for her delirium?