From sedation to continuous sedation until death: how has the conceptual basis of sedation in end-of-life care changed over time?

CONTEXT: Numerous attempts have been made to describe and define sedation in end-of-life care over time. However, confusion and inconsistency in the use of terms and definitions persevere in the literature, making interpretation, comparison, and extrapolation of many studies and case analyses problematic. OBJECTIVES: This evidence review aims to address and account for the conceptual debate over the terminology and definitions ascribed to sedation at the end of life over time. METHODS: Six electronic databases (MEDLINE, PubMed, Embase, AMED, CINAHL, and PsycINFO) and two high-impact journals (New England Journal of Medicine and the British Medical Journal) were searched for indexed materials published between 1945 and 2011. This search resulted in bibliographic data of 328 published outputs. Terms and definitions were manually scanned, coded, and linguistically analyzed by means of term description criteria and discourse analysis. RESULTS: The review shows that terminology has evolved from simple to complex terms with definitions varying in length, comprising different aspects of sedation such as indications for use, pharmacology, patient symptomatology, target population, time of initiation, and ethical considerations, in combinations of a minimum of two or more of these aspects. CONCLUSION: There is a pressing need to resolve the conceptual confusion that currently exists in the literature to bring clarity to the dialogue and build a base of commonality on which to design research and enhance the practice of sedation in end-of-life care.