Abstract
Claessens and colleagues presented data on 266 patients of whom 20 received palliative sedation before death. 1 The main study finding was that sedatives deliberately depressed the level of consciousness as measured by the Glasgow Coma scale (GCS). Administering sedatives to induce continuous deep sedation decreased the GCS from 15 to 3 and death ensued within an average of 2.5 days. In the control patients with no sedation, the GCS decreased from 15 to 9, with an average time of 10 days before death. The decline in consciousness that was characteristic of the natural dying process ensued gradually over several days in contrast to the abrupt decrease in consciousness when sedatives were administered. One inference, from Claessens and colleagues’ data, was that inducing deep sedation with sedatives had a life-shortening effect of 7.5 days. A second inference was that the lethality of deep sedation was not necessarily confined to possible dehydration but might also be related to the depression of the brain stem vital (cardiovascular, respiratory, and bulbar) centers by sedatives in these patients. 2 The depression of vital functions rather than dehydration could explain the short time to death after initiating deep sedation.
Neurophysiologic monitoring of brain activity has verified possible dissociation of the 2 components of human consciousness that is, 1) the level of consciousness (wakefulness) and 2) the content of consciousness (central awareness). 3 Claessens and colleagues rely on the level of wakefulness and depth of sedation as the surrogate marker of palliative efficacy and the relief of distress to uphold the rule of proportionality and intention in end-of-life care. 1 The rule of proportionality, when administering sedatives in end-of-life care, requires serial measurement of reliable and objective surrogates of central distress associated with the palliated symptoms (eg, pain) and titrating the drug dose to achieve the desired response of suppressing central perception that is, awareness. Internal awareness of nociception and affective emotions are not necessarily proportional to the depth of sedation and absent wakefulness. 4 Internal awareness may persist in patients who are rendered unresponsive or uncommunicative because of sedatives, opioids, general anesthesia, or neurological conditions that can impair consciousness.5 –8 There is no rigorous scientific evidence or high-quality clinical studies validating that pharmacologically induced coma always relieve inner awareness of distress or suffering at the end of life.
We think that the Claessens and colleagues have presented clinical evidence which proves that administering sedatives to induce deep sedation has a measurable life-shortening effect. The study has not provided appropriate evidence to validate the palliative efficacy and the proportionality rule regarding the use of sedatives in end-of-life care to effectively abolish awareness. We urge for more high-quality clinical research to determine the palliative efficacy of sedatives in controlling central perception of distress in unresponsive patients.