A 55-year-old post-CABG patient develops acute-onset fluctuating confusion, disorganised speech, and visual hallucinations on day 2. He is agitated at night but somnolent during the day. His oxygen saturation is 94% on room air and Na is 131 mEq/L. The most likely diagnosis is:

• A Hospital-acquired dementia
• B ICU-acquired psychosis
• C Alcohol withdrawal seizures
• D Postoperative delirium ✓

Explanation

Postoperative delirium is characterised by the acute onset of fluctuating confusion, disorganised thinking, and perceptual disturbances (visual hallucinations) occurring typically on day 1–3 after major surgery. Key features are the fluctuating course and disturbance of attention, distinguishing it from dementia (insidious, non-fluctuating). Contributing factors here include hypoxia, hyponatraemia, pain medications, and surgical stress. Delirium is the most common psychiatric complication in medically hospitalised patients. Management includes identifying and correcting precipitants, non-pharmacological reorientation, and low-dose haloperidol for agitation.

Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.

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Written and medically reviewed by the StethoPrep medical team.