In an elderly male with suddenly altered mental status after surgery, what is the most likely cause?

In an elderly male who exhibits suddenly altered mental status following surgery, delirium is the most likely cause. Delirium is characterized by acute changes in attention and cognition and can develop rapidly, especially in response to factors such as surgery, medications, pain, infection, or electrolyte imbalances.

Elderly patients are particularly vulnerable to delirium due to a combination of physiological changes associated with aging and the stress of surgery. Postoperative delirium often manifests as confusion, disorientation, and fluctuations in awareness, making it a common occurrence in this scenario.

In comparison, stroke typically presents with a sudden onset of focal neurological deficits, which may not directly align with "altered mental status" alone. Dementia, while it can cause changes in mental status, usually manifests gradually over time and is less likely to present acutely after an event like surgery. Psychosis, although it can involve alterations in perception and thinking, is not as commonly associated with the acute postoperative context in elderly patients as delirium is.

Overall, the acute nature, temporal association with surgery, and the risk factors present in the elderly make delirium the most probable explanation for the sudden change in mental status.