Dreaming during anaesthesia: a scoping review.

Dreaming during anaesthesia is common and has been documented for over a century, but remains poorly understood. This review of 157 studies from 1921 to 2024 involving 87,866 participants found that dream recall rates vary widely, from 3% to 8% in large clinical trials to 40% to 80% in experimental settings. Ketamine and propofol are most consistently associated with recall. Dreams are predominantly pleasant and feature everyday autobiographical content. Dream recall is not linked to intraoperative awareness, challenging the idea that dreams indicate inadequate anaesthetic depth. Higher home dream recall, preoperative suggestion, and immediate post-emergence assessment increase recall rates. Unpleasant dreams reduce willingness to undergo the same anaesthetic again. The positive nature and suggestibility of anaesthesia dreams suggest potential therapeutic uses.

Study at a glance

Abstract

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.