Delirium is defined as a condition of disturbed consciousness, with reduced ability to focus, sustain or shift attention. The DSM 5 - revised diagnostic criteria for delirium require:
Delirium may be
Delirium is extremely common in palliative care patients, with estimates that over 40 percent of patients will experience delirium and the prevalence increasing to over 80 per cent at the end of life. [15-17] Toward the end of life delirium, when combined with agitation may also be referred to as terminal restlessness. Delirium is an independent predictor of mortality. [5,6,15,18]
Delirium is underdiagnosed, due in part, to the difficulty in assessing it. [3,15] It remains challenging to diagnose, particularly in children  and older people.  Hypoactive delirium in particular is under-diagnosed and is the most frequent subtype of delirium in palliative care settings.  In a recent systematic review an issue identified with screening or diagnostic tools for delirium were the level of training required to use them and the length of time it takes to administer them.  Some of the more commonly used screening tools are the Confusion Assessment Method (CAM), which requires specific training for optimal use, the Delirium Rating Scale, which appears to work best in older patients, and the Memorial Delirium Assessment Scale, may be best used to measure delirium severity. [12,22] Another review also recommended the Observational Scale of Level of Arousal (OSLO) and the Richmond Agitation and Sedation Scale (RASS) as easy to use and appropriate for use in older people.  Assessment of delirium is difficult in children and there is low level evidence to support assessment tools for this group. 
Terminal restlessness is a cluster of symptoms and perhaps is a poorly understood and overly used term in the palliative care community. Most often described are a combination of agitation and altered mental state, occurring close to the end of life and may be referred to as agitated delirium.  There is no agreed definition of this condition. Its relationship with delirium, and its management and potential for reversibility are poorly understood. Assessment must include a consideration of alternative diagnoses. The differential diagnosis for this symptom complex may include: delirium, poorly controlled physical symptoms such as pain, itch, urinary retention or faecal impaction in a patient who is obtunded; akathisia, myoclonus and other movement disorders; partial complex seizures; paraneoplastic limbic encephalitis; and PTSD or other psychotic disorder.
Delirium may be reversible, although there is evidence that in some patients it can be persistent  and associated with longer term cognitive problems.  Much of the evidence about prognosis and treatment of delirium comes from the aged care and critical care literature. However, the focus of care in these populations may be different from that in palliative care, particularly in very advanced disease.  In palliative care patients, delirium is frequently multifactorial, and when the main precipitant is irreversible, or due to other factors (for example patient wishes, risk or burden of the interventions) the decision may be made not to pursue active investigation.
Factors which should be considered as possible contributors to delirium in a palliative care patient, and treated as appropriate, include:
When delirium is determined as a cause of distress in a dying patient, sedation may be the appropriate goal of treatment, and antipsychotics and benzodiazepines are currently the mainstay of therapy.  See pharmacological management. Non pharmacological approaches to delirium in the last days of life can always be implemented.
Delirium can have a distressing effect on family and carers. The high levels of stress experienced by the family of patients with delirium may be exacerbated by the potential irreversibility of the condition and the concern that the patient may die before the delirium abates.  Providing carers with information about the causes and potential course of delirium can be useful and reduce distress.  Caregivers also found information about how to act around people with delirium useful. 
Treatment of delirium is addressed in greater detail in sub-sections on:
Last updated 27 August 2021