This open-label, randomized crossover study in healthy adults tests two propofol protocols to produce distinct experiential states. One induces brief loss of responsiveness with spontaneous emergence, intended to elicit dream reports; the other maintains light sedation without loss of responsiveness, intended to elicit non-dream experiences while participants remain responsive. The main goals are to (a) measure the protocol-concordant experiential report rate (how often each method produces its intended experience), (b) explore EEG correlates of these experiences in the two states, and (c) describe their phenomenology (what they are like). We will also examine short-term changes in well-being and sleep related to these experiences. Participants complete four sessions (two of each method) with EEG and routine monitoring, immediate post-session interviews, and brief questionnaires and daily sleep/dream logs before and after anesthesia sessions.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
NONE
Enrollment
15
Intravenous propofol infusion that meets the criteria: (1) maintenance of spontaneous ventilation, (2) sedation level corresponding to a Patient State Index (PSI) no lower than 25; and (3) loss of responsiveness (LOR) defined by the Richmond Agitation Sedation Scale (RASS) = -5 \[unarousable\]. Anesthesia is then maintained at that level for 30 minutes, followed by spontaneous emergence.
Intravenous propofol infusion titrated stepwise to reach a state where participants are sedated but have behavioral responsiveness. Sedation is maintained at this level for 30 minutes.
Stanford University
Stanford, California, United States
Protocol-concordant experiential report
Presence vs absence of an experiential report elicited via a structured interview (modified Brice). "Protocol-concordant" is defined as: LOR protocol-success = any dream report upon emergence; Light-sedation (no-LOR) protocol-success = any experiential report that is not a dream (e.g., imagery, sounds, thoughts, bodily sensations, hypnagogic-like experiences) while the participant remained behaviorally responsive.
Time frame: Assessed within 5 minutes of return of responsiveness (LOR protocol) or within 5 minutes of session end (light-sedation protocol).
EEG correlates of protocol-concordant experiential outcome
EEG correlates of the two protocols/states, examining spectral band powers, band ratios, and other features during the matched windows and their association with protocol-concordant experiential outcomes.
Time frame: Matched-duration EEG windows during the 30-minute maintenance period: pre-emergence window prior to return of responsiveness in the LOR protocol, and a time-matched window during maintenance in the no-LOR protocol.
Phenomenology of anesthesia experiences (analysis of narrative reports)
Transcriptions of audio-interviews and analysis of these using (i) codebook-based content analysis, (ii) phenomenological thematic/structural coding, and (iii) NLP-derived text features.
Time frame: Interview immediately post-session
Phenomenology of anesthesia experiences (self-ratings)
Participants' own ratings of their anesthesia experiences: complexity, vividness, affect (valence/intensity), meaningfulness, dynamism/movement, bizarreness, perceived duration, the degree of mystical experiences (Mystical Experience Questionnaire; Barrett et al., 2015) and challenging experiences (Challenging Experience Questionnaire; Strickland et al., 2024).
Time frame: Interview immediately post-session
Dream vs dream-like experiences (within-anesthesia) - phenomenological differences
Comparison of phenomenology between anesthesia dreams (LOR protocol) and dream-like experiences (light sedation no-LOR protocol) based on the analysis of narrative reports and self-ratings of the experiences
Time frame: Interview immediately post-session
Home dreams vs anesthesia dreams - phenomenological differences
Differences in phenomenology of home dreams vs anesthesia dreams based on the analysis of narrative reports and self-ratings of these experiences
Time frame: Home dream logs (2 weeks pre-session and 2 weeks post-session) vs anesthesia interview (immediate post-session).
Safety outcomes
Incidence of adverse events during anesthesia or recovery (e.g., PONV; hypoxemia; hypotension; airway intervention) and any serious adverse events per FDA criteria.
Time frame: From pre-anesthesia baseline to post-anesthesia discharge
Changes in daily mood
As measured with the following mood scales: PANAS (Watson et al., 1988) and items from the 12-point Affect Circumplex (Yik et al., 2011)
Time frame: Baseline (2-week pre-session average) to follow-up (2-week post-session average)
Change in well-being: life satisfaction
As measured with The Satisfaction With Life Scale (Diener et al., 1985)
Time frame: Baseline (2-weeks pre-anesthesia) to follow-up (2-weeks post-anesthesia)
Change in well-being: peace of mind
As measured with The Peace of Mind Scale (Lee et al., 2013)
Time frame: Baseline (2-weeks pre-anesthesia) to follow-up (2-weeks post-anesthesia)
Change in sleep quality
Change in sleep quality as measured using the Pittsburgh Sleep Quality Inventory (PSQI; Buysse et al., 1989) and daily sleep and dream diaries
Time frame: Baseline (2-week pre-session) to follow-up (2-week post-session)
Change in dream outcomes
Change in dream recall frequency, occurrence of nightmares, nightmare distress as measured using the Mannheim Dream Questionnaire (MADRE; Schredl et al., 2014) and daily dream diaries
Time frame: Baseline (2-week pre-session) to follow-up (2-week post-session).
Change in well-being: harmony in life
As measured with the Harmony in Life Scale (Kjell et al., 2016)
Time frame: Baseline (2-weeks pre-anesthesia) to follow-up (2-weeks post-anesthesia)
Change in well-being: psychological (eudaimonic) well-being
As measured with the Psychological Well-Being Scale (Ryff, 1989)
Time frame: Baseline (2-weeks pre-anesthesia) to follow-up (2-weeks post-anesthesia)
Change in alexithymia score
As measured with the Perth Alexithymia Questionnaire Short Form (Preece et al., 2023)
Time frame: Baseline (2-weeks pre-anesthesia) to follow-up (2-weeks post-anesthesia)
Change in emotion regulation
As measured with the Emotion Regulation Questionnaire (Gross \& John, 2003) and the Perth Emotion Regulation Competency Index (Preece et al., 2018)
Time frame: Baseline (2-weeks pre-anesthesia) to follow-up (2-weeks post-anesthesia)
Change in symptoms of depression
As measured with the depression module of the Patient Health Questionnaire (PHQ9; Spitzer et al., 1999)
Time frame: Baseline (2-weeks pre-anesthesia) to follow-up (2-weeks post-anesthesia)
Change in symptoms of anxiety
As measured with the The Generalized Anxiety Disorder Scale (GAD-9; Spitzer et al., 2006)
Time frame: Baseline (2-weeks pre-anesthesia) to follow-up (2-weeks post-anesthesia)
Change in perceived loneliness
As measured the 3-item UCLA Loneliness Scale (Hughes et al., 2004)
Time frame: Baseline (2-weeks pre-anesthesia) to follow-up (2-weeks post-anesthesia)
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