Dreaming during anaesthesia: a scoping review

Dreaming during anaesthesia has been documented for over a century, yet it remains poorly understood. This scoping review synthesises evidence on the frequency, phenomenology, predictors, outcomes, and neural correlates of anaesthesia dreaming.

We systematically searched multiple databases for studies examining anaesthesia dreaming, including clinical trials, observational studies, and experimental investigations in adult and paediatric patients, as well as in healthy volunteers.

We identified 157 studies (1921-2024) involving 87 866 participants. Dream recall varied widely, with higher rates in experimental settings (often 40%-80%) compared with large-scale clinical trials (typically 3%-8%), likely reflecting methodological differences. Ketamine (clinical: 0%-95%; experimental: 44%-100%) and propofol (clinical: 0%-64%; experimental: 0%-77%) were most consistently associated with recall. Dreams were predominantly pleasant, featuring everyday autobiographical content. Higher home dream recall frequency, preoperative suggestion or priming, and immediate post-emergence assessment were associated with higher recall. Evidence regarding clinical outcomes was limited, but unpleasant dreams were linked to lower willingness to undergo the same anaesthetic again. Dream recall was not associated with intraoperative awareness, challenging interpretations of dreams as markers of inadequate anaesthetic depth. Emerging neural evidence suggests that dreaming exhibits signatures distinct from unconsciousness and connected consciousness.

Anaesthesia dreaming is common, predominantly positive, and pharmacologically specific. Major gaps in knowledge include inconsistent definitions, inadequate assessment methods, limited mechanistic understanding, sparse paediatric research, and minimal outcome data. Standardised approaches informed by consciousness science and sleep research are needed. The positive nature and suggestibility of anaesthesia dreams suggest potential therapeutic applications warranting investigation.