Palliative sedation can be defined as a controlled induction of sedation, sometimes to the point of unconsciousness, to relieve the severe, refractory suffering of a terminally ill patient (Krakauer [76], Twycross [155]). It is important to distinguish between normal palliative sedation and deep sedation. Normal sedation occurs commonly at the end of life for a variety of reasons. Deep sedation is for severe suffering that is refractory to all reasonable and aggressive treatment including normal sedation (Prado et al. [120], Twycross [155]).

The most fundamental task of palliative medicine is to relieve suffering (Cassel [22]). For some patients, suffering continues to be uncontrolled despite specialist measures employed to relieve it. Controlled sedation can on rare occasions be the only effective way to relieve the patient's anguish (Krakauer [76]).

Recognition that the patient is dying and is in the final hours or days of life is paramount to providing effective terminal sedation. For a patient to be considered for sedation, they must be deemed to be suffering from one or more severe physical or neuropsychiatric symptoms, including but not limited to pain, dyspnoea, vomiting, seizures, agitated delirium, anxiety or depression. The symptoms must be refractory to standard palliative interventions such as medications, nerve blocks, palliative radiotherapy or other treatments offered by specialists in pain and psychiatry. Comfort must be the most important goal of the patient's care (Krakauer [76]). A DNaCPR order should be in place and the decision to sedate should be discussed with the patient where possible, as well as the family. It is also imperative to consult the wider multidisciplinary team in order to ensure any concerns are discussed. This procedure involves the support of a specialist palliative care team. Where deep sedation is considered, the expertise of an anaesthetist may be necessary.