Acute Confusional State (ACS): Definition, Symptoms & Causes

Acute confusional state (synonymous with delirium) is a sudden, fluctuating disturbance in attention, awareness, and cognition.

Core Features

• Acute onset (hours to days) and fluctuating course
• Inattention and distractibility
• Disorientation (time, place, person)
• Memory impairment (especially recent)
• Disorganized thinking, rambling speech
• Perceptual disturbances (hallucinations, illusions)
• Altered psychomotor activity (agitation or lethargy)
• Sleep-wake cycle reversal

Common Causes

• Infections (UTI, pneumonia, sepsis)
• Medication side effects (anticholinergics, opioids, benzodiazepines)
• Electrolyte/metabolic imbalances (hyponatremia, hypercalcemia, uremia)
• Drug/alcohol withdrawal
• Neurologic events (stroke, seizure)
• Post-operative state

ACS is a medical emergency requiring prompt identification and treatment of the underlying cause.