Elsevier

Resuscitation

Volume 85, Issue 12, December 2014, Pages 1799-1805
Resuscitation

Clinical Paper
AWARE—AWAreness during REsuscitation—A prospective study

https://doi.org/10.1016/j.resuscitation.2014.09.004Get rights and content

Abstract

Background

Cardiac arrest (CA) survivors experience cognitive deficits including post-traumatic stress disorder (PTSD). It is unclear whether these are related to cognitive/mental experiences and awareness during CPR. Despite anecdotal reports the broad range of cognitive/mental experiences and awareness associated with CPR has not been systematically studied.

Methods

The incidence and validity of awareness together with the range, characteristics and themes relating to memories/cognitive processes during CA was investigated through a 4 year multi-center observational study using a three stage quantitative and qualitative interview system. The feasibility of objectively testing the accuracy of claims of visual and auditory awareness was examined using specific tests. The outcome measures were (1) awareness/memories during CA and (2) objective verification of claims of awareness using specific tests.

Results

Among 2060 CA events, 140 survivors completed stage 1 interviews, while 101 of 140 patients completed stage 2 interviews. 46% had memories with 7 major cognitive themes: fear; animals/plants; bright light; violence/persecution; deja-vu; family; recalling events post-CA and 9% had NDEs, while 2% described awareness with explicit recall of ‘seeing’ and ‘hearing’ actual events related to their resuscitation. One had a verifiable period of conscious awareness during which time cerebral function was not expected.

Conclusions

CA survivors commonly experience a broad range of cognitive themes, with 2% exhibiting full awareness. This supports other recent studies that have indicated consciousness may be present despite clinically undetectable consciousness. This together with fearful experiences may contribute to PTSD and other cognitive deficits post CA.

Introduction

The observation that successful cardiac arrest (CA) resuscitation is associated with a number of psychological and cognitive outcomes including post-traumatic stress disorder, depression and memory loss as well as specific mental processes that may share some similarities with awareness during anaesthesia,1, 2 has raised the possibility that awareness may also occur during resuscitation from CA.3 In addition to auditory perceptions, which are characteristic of awareness during anesthesia, CA survivors have also reported experiencing vivid visual perceptions, characterized by the perceived ability to observe and recall actual events occurring around them.4 Although awareness during anesthesia is associated with dream like states, the specific mental experience described in association with CA is unknown. CA patients have reported visual perceptions together with cognitive and mental activity including thought processes, reasoning and memory formation.3 Patients have also been reported to recall specific details relating to events that were occurring during resuscitation.4

Although there have been many anecdotal reports of this phenomenon, only a handful of studies have used rigorous research methodology to examine the mental state that is associated with CA resuscitation.4, 5, 6, 7 These studies have examined the scientifically imprecise yet commonly used term of ‘near-death experiences’ (NDE).3 While NDE have been reported by 10% of CA survivors,3 the overall broader cognitive/mental experiences associated with CA, as well as awareness, and the association between actual CA events and auditory/visual recollection of events has not been studied. The primary aim of this study was to examine the incidence of awareness and the broad range of mental experiences during resuscitation. The secondary aim was to investigate the feasibility of establishing a novel methodology to test the accuracy of reports of visual and auditory perception and awareness during CA.

Section snippets

Methods

In this multicenter observational study, methods were initially pilot tested at 5 hospitals prior to study start-up (01/2007–06/2008) at which point the study team recruited 15 US, UK and Austrian hospitals (out of an original selected group of 25) to participate in data collection. Between 07/2008 and 12/2012 the first group of CA patients were enrolled in the AWARE study. These patients were identified using a local paging system that alerted staff to CA events. CA patients were eligible for

Results

A total of 2060 CA events were recorded with an average 16% (n = 330) overall survival to hospital discharge. Of the 330 survivors, 140 patients were found eligible, provided informed consent, and were interviewed. Fifty-two interviews were completed in-hospital and 90 after discharge. Two patients refused interview and the remaining 188 patients either did not meet inclusion criteria, died after hospital discharge, were not deemed suitable for further follow up by their physicians, or did not

Discussion

Our data suggest that CA patients may experience a range of cognitive processes that relate both to the CA and post-resuscitation periods. Although, the relatively high proportion of patients who perceived having memories and awareness was unexpected and should be confirmed through future research, the fact that the observed frequency of NDE (9%) in our study was consistent with reports from prior studies (approximately 10%),4, 5, 6, 7 may provide some measure of internal validity for this

Conclusions

CA survivors experience a broad range of memories following CPR including fearful and persecutory experiences as well as awareness. While explicit recall of VA is rare, it is unclear whether these experiences contribute to later PTSD. Studies are also needed to delineate the role of explicit and implicit memory following CA and the impact of this phenomenon on the occurrence of PTSD and other life adjustments among CA survivors.

Conflict of interest statement

None of the authors have any conflicts of interest to declare.

Financial support

Resuscitation Council (UK), Nour Foundation, Bial Foundation. Researchers worked independent of the funding bodies and the study sponsor. Furthermore, the study sponsor did not participate in study design, analysis and interpretation of results or the writing of the manuscript.

Ethical approval

This study obtained ethics approvals from each participating center prior to the start of recruitment and data collection. Each surviving patient gave informed consent prior to their being interviewed.

Data sharing

All authors either had access to all the data or the opportunity to review all data.

Transparency declaration

I Sam Parnia as lead author affirm that the manuscript is an honest, accurate, and transparent account of the study being reported and that no important aspects of the study have been omitted and that any discrepancies from the study as planned have been explained.

Acknowledgements

We acknowledge the Biostatistical Consultation and support from the Biostatistical Consulting Core at the School of Medicine, Stony Brook University as well as the help of Dr's Ramkrishna Ramnauth, Vikas Kaura, Markand Patel, Jasper Bondad, Markand Patel, Georgina Spencer, Jade Tomlin, Rav Kaur Shah, Rebecca Garrett, Laura Wilson, Ismaa Khan, and Jade Tomlin with the study.

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    A Spanish translated version of the summary of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2014.09.004.

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