If a patient appears delirious, you should search for the underlying cause. The mnemonic DELIRIUM is helpful to recall some of them:

D rugs: Medication side effects
E lectrolyte abnormalities
L ack of drugs – Withdrawal from a medication …
I nfection
R educed sensory input – Patients who are hard of hearing or have impaired vision
I ntracranial pathology
U rinary or fecal retention
M yocardial and pulmonary – Infarction, CHF exacerbation, COPD exacerbations, and other disease processes that cause hypercapnia or hypoxia