Delirium is also known as acute confusional state, altered mental status, and toxic metabolic encephalopathy, among more than 30 descriptive terms. Delirium can be thought of as acute brain failure and is the final common pathway of multiple mechanisms, similar to acute heart failure. The official definition of delirium in the Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5), requires a disturbance in attention and awareness that develops acutely and tends to fluctuate. The pathophysiological mechanisms of delirium remain poorly understood; leading models include neurotransmitter imbalance and neuroinflammation.
Two scales are in common use, the Confusion Assessment Method for the ICU (CAM-ICU) and the Intensive Care Delirium Screening Checklist (ICDSC).