Consciousness During CPR: ALS TF Scoping Review

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This CoSTR is a draft version prepared by ILCOR, with the purpose to allow the public to comment and is labeled “Draft for Public Comment". The comments will be considered by ILCOR. The next version will be labelled “draft" to comply with copyright rules of journals. The final COSTR will be published on this website once a summary article has been published in a scientific Journal and labeled as “final”.

Conflict of Interest Declaration

West, Otto, Rudd, Soar have No COI

Sam Parnia* – published about awareness and has subject matter expertise. He has received grants in the past on this area but holds no current grant

Bernd Böttiger* – published a letter about CPR induced consciousness

*Neither SP or BWB involved in selection of studies/ data extraction

Task Force Scoping Review Citation

R.L. West, Q. Otto, I. R. Drennan, S. Rudd, S. Parnia, B. W. Böttiger, J. Soar, on behalf of the International Liaison Committee on Resuscitation Advanced Life Support Task Force.

CPR-related cognitive activity, consciousness, awareness and recall and its management: Scoping Review and Task Force Insights [Internet] Brussels, Belgium: International Liaison Committee on Resuscitation (ILCOR) Advanced Life Support Task Force, 2021 Feb 1st. Available from:

Methodological Preamble and Link to Published Scoping Review

The continuous evidence evaluation process started with a scoping review of adult life support conducted by the ILCOR ALS Task Force Scoping Review team. Evidence for literature was sought and considered by the Advanced Life Support Adult Task Force.

Scoping Review

R.L. West, Q. Otto, I. R. Drennan, S. Rudd, S. Parnia, B. W. Böttiger, J. Soar, on behalf of the International Liaison Committee on Resuscitation Advanced Life Support Task Force. CPR-related cognitive activity, consciousness, awareness and recall and its management: Scoping Review. In preparation.


The PICOST (Population, Intervention, Comparator, Outcome, Study Designs and Timeframe)

Population: Adults in any setting with consciousness during CPR

Intervention: Sedation, analgesia, or other intervention to prevent consciousness

Comparators: No specific intervention for consciousness

Outcomes: Any clinical outcome. Arrest outcomes and psychological wellbeing post arrest

Other relevant outcomes identified from the review where included such as rescuer outcomes including, rescuer distress, and trauma.

Study Designs: Randomized controlled trials (RCTs) and non-randomized studies (non-randomized controlled trials, interrupted time series, controlled before-and-after studies, cohort studies) were all eligible for inclusion. For the purpose of the scoping review, we also included Case reports and case series, Grey literature and unpublished studies (e.g., conference abstracts, trial protocols). Articles based around the Lazarus phenomenon and cough CPR as well as narrative articles referring to near death experiences and consciousness were excluded but noted for discussion.

Timeframe: All years and languages were included providing an English title or abstract was given, up until 24th November 2020

Search Strategies


PRISMA Diagram


Data tables


Task Force Insights

1. Statement about why this topic was reviewed

  • CPR induced consciousness noted by rescuers is increasingly described. In addition patients describe recall of CPR events
  • In the past the poorly defined umbrella term of 'near death experiences (NDEs)' has been used to refer to cardiac arrest (CA) experiences - this does not adequately describe the breadth of these experiences. Survivor experiences encompass multiple themes, which can occur at different times in relation to their CA, CPR, and post-CA recovery. These include transcendent mystical experiences, visual and auditory awareness with a perceived sense of bodily detachment, dream like states, CPR-induced consciousness, as well as conscious experiences related to emergence from coma. Furthermore, it is unclear whether explicit recall reflects the entirety of conscious experiences or whether, there may also be implicit learning without recall of events, similar to accidental awareness during anaesthesia.
  • We will describe the specific experiences and whether any interventions have been used to prevent them e.g. use of sedatives.
  • This scoping review aims to identify the available studies on this topic, and whether a systematic review is required.

2. Narrative summary of evidence identified

  • We identified 5 observational studies (Table 1) looking at various aspects of sedation and consciousness, and 24 cases reports (Table 2) including 31 patients.
  • Based on 2 observational studies [Olaussen 2016 44; Doan 2020 769] with 39569 patients, CPR induced consciousness has an estimated true prevalence rate of between 0.23% to 0.7%.
  • One observational study of 100 healthcare professionals estimated 51-59% had experienced a case of CPR induced consciousness [Olaussen 2016 186]. Estimates were based on the assumption that all non-responders to the questionnaire had no experience the phenomena.
  • A high proportion of patients who experience CPR induced consciousness have a professional rescuer witnessed cardiac arrest with a shockable rhythm.
  • Patients experiencing CPR induced consciousness showed increased rates of ROSC, survival to hospital and survival to discharge when compared to patients not showing signs of CPR induced consciousness.
  • Awareness may also be present without the overt signs of consciousness.
  • Some cases may have occurred where there is a low flow state and true cardiac arrest has not occurred, or ROSC has already been achieved, and reports do not adequately address this issue.
  • Rescuer distress is a common negative result of CPR induced consciousness.
  • Sedation was rarely used in CPR induced consciousness.
  • The observational studies showed a pharmacological intervention rate ranging from 11.5% in a patient population of 52 patients [Doan 2020 769], and by 27% (in non-CPR interfering) and 39.7% (in CPR interfering) of healthcare professionals [Olaussen 2016 186].
  • The case studies showed pharmacological intervention was used in 28.5% of patients.
  • Giving sedation / analgesia either as a bolus or continuous infusion during the resuscitation attempt had no impact on whether that patient went on to develop PTSD [Gamper 2004 378].
  • The use of sedation / analgesia may negatively impact the resuscitation outcome in terms of survival.
  • Optimal drug dosing regimen during CPR is uncertain, and several local protocols are available (Figure 1.)
  • We did not specifically look at:
  • Phenomena surrounding CPR induced consciousness such as the Lazarus phenomena, cough CPR and consciousness during cardiac arrest with a ventricular assist device in situ
  • Near death experiences, their prevalence or the physiology potentially causing this phenomenon.

3. ALS Task Force discussions

  • The TF decided there was insufficient information at this time to warrant a formal systematic review.
  • Distinguishing between different overt physical signs of consciousness and transcendental cognitive experiences as the psychological impact may vary greatly – Patients with physical signs of consciousness are more likely to experience pain and distress than those with “out of body type experiences” and thus optimal management may be different.
  • CPR induced consciousness probably signifies early sudden cardiac arrest or effective brain circulation from CPR. It's effects on the patient are poorly understood.
  • Some patient recall of events during CPR may actually relate to events that occurred after ROSC and during recovery.
  • Patients may have explicit recall of events during recovery that they volunteer or recall after prompting.
  • There needs to be a wider recognition of patient cognitive experiences amongst clinicians. Many patients are afraid to discuss these experiences as they feel clinicians will not be receptive.
  • There is a need for space to discuss these experiences, and awareness of resources available to manage ongoing problems such as PTSD in both patients and rescuers.
  • The Task Force discussed whether survival both with and without PTSD would be considered a favourable outcome in a patient showing signs of consciousness during CPR and likely to be an acceptable outcome for individuals compared to survival with a poor functional or cognitive outcome or death.
  • There is an absence of standardised reporting criteria for the different experiences patients might experience.
  • The optimal drugs and doses are unknown in terms of speed of effect and impact on cardiac arrest outcomes. Drugs may have harmful cardiovascular effects and, or beneficial neuroprotective effects.
  • There is not enough evidence to produce standardized guidelines. However, given the interest in this topic, there is a need to for a good practice statement:
  • The TF made the following suggestions
    • In setting where it is feasible, rescuers should consider giving sedative and, or analgesic drugs in very small doses to prevent pain and distress to patients who are conscious during CPR (good practice statement).
  • Neuromuscular blocking drugs should not be given to conscious patients (good practice statement).
  • The optimal choice of drugs for sedation and analgesia during CPR is uncertain. Drug regimens should be based on those used in critically-ill patients and according to local protocols (good practice statement).


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