Forum.
LITERATURE REVIEW
Summarising the use of these drugs as reported in the literature is made difficult by:
- a lack of a standardised definition of sedation, goal of therapy and its assessment(1)
- a frequent lack of a description of the specific symptom for which sedation is used
- the existence of several indications for the use of most sedative drugs
- a lack of data on doses used.
Definitions of sedation
Very few studies provide a definition of sedation. One example, "deliberately inducing and maintaining deep sleep for the relief of intractable physical or mental symptoms (but excluding delirium)" was not acceptable to many palliative care physicians, but no single alternative view existed.(2)
Many, perhaps most, palliative medicine physicians do not appear to prescribe sedatives in order to primarily induce a deep sleep. Instead the dose of sedative is titrated against the level of a patients’ distress, just as the dose of morphine is titrated against pain severity. If distress is relieved while the patient remains conscious this is seen as an adequate degree of sedation. Some have characterised this titration approach to the use of sedatives as "proportional" and that of deliberately inducing deep sleep as "sudden".(3) These terms have been used in this summary (Tables 1 and 2). However, it is not always clear ( I’m still being picky!) which approach has been adopted.(3,4) Some authors also suggest differentiating between inducing ‘tranquilisation’ (patient calm while still alert) from ‘sedation’ (not only tranquil but with reduced consciousness ranging from drowsiness to deep sleep).(5)
Whatever the name given to the procedure, it involves:
- sedation induced with a non-opioid in a terminally ill patient with advanced incurable disease
- refractory distress
- no intention to cause death
- informed consent by the patient or the patient’s surrogate. (6)
Definitions of symptoms
Unequivocal definitions for some symptoms, especially psychological ones are lacking. For example, ‘existential or family distress’ is a common reason for the use of sedation in some countries, but is entirely absent in others.(7) Some of this difference may be cultural, as the same symptom or behaviour may be termed differently across countries and cultures e.g. "mental anguish", “restlessness” or “agitated delirium”.(7-9) It has been suggested that in respect of existential distress some of the differences may be genuine and be a reflection of much lower levels of disclosure of information during the trajectory of the illness in some countries than in others. The result may be a degree of psychological distress that appears as the patient's physical deterioration reveals to him or her a truth that is unmentionable verbally.(7) Although there is broad agreement about the most common indications for use of sedatives at the end of life, these differences require more definitive exploration.
Indication for which the drug is being used
Drugs may have several indications for their use. In retrospective studies in particular, it may be difficult to distinguish, e.g. if levomepromazine or haloperidol are being used primarily for their antipsychotic or anti-emetic properties. Dose may be a guide to the purpose of their use but often no data are presented. Some have restricted their analysis to patients with daily doses of haloperidol, levomepromazine or midazolam greater or equal to 20mg, 25mg and 10mg respectively.(10) This introduces another source of inconsistency that makes comparing studies difficult.
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