Subjective experiences during dexmedetomidine- or propofol-induced unresponsiveness and non-rapid eye movement sleep in healthy male subjects

Abstract

<p>Background: Anaesthetic-induced unresponsiveness and non-rapid eye movement (NREM) sleep share common neural pathways and neurophysiological features. We hypothesised that these states bear resemblance also at the experiential level. <br></p><p>Methods: We compared, in a within-subject design, the prevalence and content of experiences in reports obtained after anaesthetic-induced unresponsiveness and NREM sleep. Healthy males (<em>N</em>=39) received dexmedetomidine (<em>n</em>=20) or propofol (<em>n</em>=19) in stepwise doses to induce unresponsiveness. Those rousable were interviewed and left unstimulated, and the procedure was repeated. Finally, the anaesthetic dose was increased 50%, and the participants were interviewed after recovery. The same participants (<em>N</em>=37) were also later interviewed after NREM sleep awakenings. <br></p><p>Results: Most subjects were rousable, with no difference between anaesthetic agents (<em>P</em>=0.480). Lower drug plasma concentrations were associated with being rousable for both dexmedetomidine (<em>P</em>=0.007) and propofol (<em>P</em>=0.002) but not with recall of experiences in either drug group (dexmedetomidine: <em>P</em>=0.543; propofol: <em>P</em>=0.460). Of the 76 and 73 interviews performed after anaesthetic-induced unresponsiveness and NREM sleep, 69.7% and 64.4% included experiences, respectively. Recall did not differ between anaesthetic-induced unresponsiveness and NREM sleep (<em>P</em>=0.581), or between dexmedetomidine and propofol in any of the three awakening rounds (<em>P</em>>0.05). Disconnected dream-like experiences (62.3% <em>vs</em> 51.1%; <em>P</em>=0.418) and memory incorporation of the research setting (88.7% <em>vs</em> 78.7%; <em>P</em>=0.204) were equally often present in anaesthesia and sleep interviews, respectively, whereas awareness, signifying connected consciousness, was rarely reported in either state. <br></p><p>Conclusions: Anaesthetic-induced unresponsiveness and NREM sleep are characterised by disconnected conscious experiences with corresponding recall frequencies and content. <br></p><p>Clinical trial registration: Clinical trial registration. This study was part of a larger study registered at ClinicalTrials.gov (NCT01889004).<br></p>