Delirium is one of the most hidden and deadly enemy in ICU. It increases mortality, it cost money and its hard to recognise.
Here is a simple mnemonics for delirium: DELIRIUM(S)
D Drugs, Drugs, Drugs
E Eyes, ears 
L Low O2 (MI, ARDS, PE, CHF, COPD) 
R Retention (of urine or stool), Restraints
(S) Subdural, Sleep deprivation
 Poor vision and hearing are considered more risk factors than true causes, but should be "fixed" or improved if possible. Cerumen is common cause of hearing impairment.
 "Low O2 states" does NOT necessarily mean hypoxia, rather it is a reminder that patients with a hypoxic insult (e.g. Ml, stroke, PE) may present with mental status changes with or without other typical symptoms/signs of these diagnoses.
An organised effort is underway in the form of website charged by Dr. E.Wesley Ely of Vanderbilt University Medical Center.