F05 Delirium due to known physiological condition

Acute or subacute brain syndrome
Acute or subacute confusional state (nonalcoholic)
Acute or subacute infective psychosis
Acute or subacute organic reaction
Acute or subacute psycho-organic syndrome
Delirium of mixed etiology
Delirium superimposed on dementia
Sundowning

Excludes1: delirium NOS (R41.0)
Excludes2: delirium tremens alcohol-induced or unspecified (F10.231, F10.921)

Code first: the underlying physiological condition, such as:
dementia (F03.9-)