Delirium is defined as a disturbance of consciousness characterized by an acute onset of impaired cognitive function. Although delirium is thought to be common in the Intensive Care Unit (ICU) there are few studies that have evaluated its incidences, risks and outcomes. It has been associated with increased morbidity, and mortality and increased cost to the healthcare system. In addition to the uncertainty of the incidence of ICU delirium, there is a lack of information about the effects that certain pharmacological treatments have on delirious patients.