Delirium is a common and severe neuropsychiatric syndrome characterised by acute deterioration and fluctuations in mental status mainly precipitated by acute illness, trauma, surgery, or the side effects of drugs. The core DSM-IV diagnostic criteria are: (a) a disturbance of consciousness (that is, reduced clarity of awareness of the environment, with reduced ability to focus, sustain, or shift attention), (b) a change in cognition (e.g. memory impairment) or a perceptual disturbance, and (c) onset of hours to days, and tendency to fluctuate. Delirium is one of the most common acute medical conditions. The overall prevalence in medical inpatients is greater than 10%; in older patients this rises to greater than 20% and in intensive care units and post-operative hip fracture patients the prevalence is greater than 50%. In a typical 1000-bedded hospital, around 120 people will have delirium at any given time. There are currently no licensed treatments.
Although by definition delirium has an acute onset and always involves attentional deficits, it is otherwise heterogeneous, with the variable presence of multiple other neuropsychiatric features. Prominent among these is disturbance in level of consciousness, which ranges from barely responsive to highly agitated. A reduced level of consciousness is termed hypoactive delirium, whereas agitation and increased motor activity is termed hyperactive delirium. Many patients fluctuate between these motoric subtypes. Other neuropsychiatric manifestations include impairments in memory, perception and other cognitive domains, psychosis, and disturbance of the sleep-wake cycle (Fong et al., 2009, MacLullich and Hall, 2011).
The time-course of delirium is highly variable. Delirium has conventionally been described as a transient disorder, and indeed it does resolve in the majority of cases. Some patients may experience only a few hours of the syndrome, while others may have more prolonged episodes lasting days or weeks. Recent research has found that around 20% still exhibit symptoms three or even six months after onset; this is termed ‘persistent delirium’ (Meagher et al., 2012). Notwithstanding the resolution of most delirium, these episodes have serious long term consequences: it is now known that delirium predicts multiple adverse outcomes, including increased length of stay, morbidity, institutionalisation, and mortality during admission and one year after discharge (Witlox et al., 2010). Moreover, in cognitively normal patients, an episode of delirium is associated with a higher risk of dementia in the years following the episode (MacLullich et al., 2009, Davis et al., 2012). Delirium is also often highly distressing for patients and carers (Fong et al., 2009, MacLullich and Hall, 2011) and may result in post-traumatic stress disorder (Davydow et al., 2008).Delirium Case History.
An 82-year-old man with a history of mild dementia, ischaemic heart disease and osteoarthritis who lived with his wife was taken to the emergency department with confusion and agitation, and productive cough and fever for 2 days. He had resisted being brought to the hospital initially but had then become drowsy and had to be lifted onto the ambulance trolley. Upon arrival he became agitated, saying that he didn’t want to be ‘locked up’, and he tried to get off the trolley to leave the hospital. With reassurance from his wife he became calmer. A few minutes later he was drowsy again. On examination he was able to say his name on request but did not respond meaningfully to other questions and only intermittently obeyed simple commands such as ‘lift up your arms’. The pulse was raised at 98 and the blood pressure was 108/64. Oxygen saturations were normal and the temperature was elevated at 37.8 °C. Chest examination revealed signs of pneumonia but chest X-ray was not possible because the patient could not tolerate the procedure. Blood tests showed a raised white cell count and evidence of mild acute kidney injury. The patient was treated with antibiotics and intravenous fluids and within one day was less agitated. His vital signs all become normal. He became more compliant with treatment and had no further episodes of agitation. However, he remained drowsy and at times was too sleepy even to exchange a few words. When awake his speech was intermittently coherent but he was unable to sustain meaningful communication for more than a few seconds at a time. He was disorientated and unable to count backwards from 20 down to 1. His wife stated that his mental status was much worse than normal. After three more days he was more consistently awake but remained unable to sustain normal conversation. He was also unsteady when walking and required assistance to do this safely. Seven days after admission he was transferred to a rehabilitation facility, and after a further two weeks his mental and physical status had improved sufficiently such that he was discharged home. However, when visited by the general practitioner two weeks later his wife reported that though he was improving he was still sometimes disorientated, and also considerably more passive and apathetic than he had been before his illness.