Near-death experiences in cardiac arrest survivors

Cybernetics as a conversation with the Cosmos

Norbert Wiener was the first to functionally define cybernetics as "the study of control and communication in the animal and the machine". Herein, it is shown that as a manifestation of physiology, cybernetics can be further reduced to cell-cell signaling to maintain homeostasis, bridging Newtonian 3rd Order Cybernetics with Quantum Mechanical 4th Order Cybernetics as our 'conversation with the Cosmos' based on Quantum Entanglement, constrained by non-localization. As such, cybernetics can be scientifically tested in toto from the functional to the metaphysical, rendered physical as communication for the first time. If that is correct, then the sooner we begin operating based on Quantum Mechanical principles, the sooner we will function based on predictive algorithms.

Near-Death Experiences and Religious Experience: An Exploration of Spirituality in Medicine

There has been a continuous discussion of religious experience since William James, culminating in a rich and varied literature on the epistemology of religious experience in the late twentieth century. There has also been a burgeoning literature on near-death experiences (NDEs), largely on neurology and physiology and sometimes as possible counterevidence to naturalism. One important subject is largely missing, and that is a discussion of NDEs as religious experiences, and what light that might shed on their epistemic status. This paper is an attempt to fill that gap. In part one, we will delineate the topic of NDEs and what medical science has to say about them. In part two, we will lay out a general view of the epistemology of religious experience. In part three, we will apply that understanding of religious experience to NDEs and draw what lessons we may.

Does Hypothermic Circulatory Arrest for Aortic Surgery Trigger Near-Death Experience? Incidence of Near-Death Experiences after Aortic Surgeries Performed under Hypothermic Circulatory Arrest

BACKGROUND

 Understanding near-death experiences (NDE) could provide a new insight into the analysis of human consciousness and the neurocognitive processes happening upon the approach of death. With a temporary interruption of systemic perfusion, aortic surgery under hypothermic circulatory arrest (HCA) may be the only available model of reversible clinical death. We present, herein, the results of an observational study designed to assess the incidence of NDE after aortic surgery.

METHODS

 We performed a prospective study including consecutive patients who underwent thoracic aortic surgery between July 2018 and September 2019 at our institution. Procedures without HCA were included to constitute a control group. The primary outcome was the incidence of NDE assessed with the Greyson NDE scale during the immediate postoperative course, via a standardized interview of the patients in the surgical ward.

RESULTS

 One hundred and one patients were included. Twenty-one patients (20.8%) underwent nonelective interventions for aortic dissection. Ninety-one patients had hemiarch replacement (90.1%). Sixty-seven (66.3%) interventions were performed with HCA, with an average circulatory arrest duration of 26.9 ± 25.5 minutes, and a mean body temperature of 23.7 ± 3.8°C. None of the patients reported any recollection from their period of unconsciousness. There was no NDE experiencer in the study cohort.

CONCLUSION

 Several confounding factors regarding anesthesia, or NDE evaluation, might have impaired the chance of NDE recollections, and might have contributed to this negative result. Whether HCA may trigger NDE remains unknown.

Electrophysiological evidence of preserved hearing at the end of life

This study attempts to answer the question: “Is hearing the last to go?” We present evidence of hearing among unresponsive actively dying hospice patients. Individual ERP (MMN, P3a, and P3b) responses to deviations in auditory patterns are reported for conscious young, healthy control participants, as well as for hospice patients, both when the latter were conscious, and again when they became unresponsive to their environment. Whereas the MMN (and perhaps too the P3a) is considered an automatic response to auditory irregularities, the P3b is associated with conscious detection of oddball targets. All control participants, and most responsive hospice patients, evidenced a “local” effect (either a MMN, a P3a, or both) and some a “global” effect (P3b) to deviations in tone, or deviations in auditory pattern. Importantly, most unresponsive patients showed evidence of MMN responses to tone changes, and some showed a P3a or P3b response to either tone or pattern changes. Thus, their auditory systems were responding similarly to those of young, healthy controls just hours from end of life. Hearing may indeed be one of the last senses to lose function as humans die.

Near-Death High-Frequency Hyper-Synchronization in the Rat Hippocampus

Near-death experiences (NDE) are episodes of enhanced perception with impending death, which have been associated with increased high-frequency (13-100 Hz) synchronization of neuronal activity, which is implicated in cognitive processes like perception, attention and memory. To test whether the NDE-associated high-frequency oscillations surge is related to cardiac arrest, recordings were made from the hippocampus of anesthetized rats dying from an overdose of the sedative chloral hydrate (CH). At a lethal dose, CH caused a surge in beta band power in CA3 and CA1 and a surge in gamma band power in CA1. CH increased the inter-regional coherence of high-frequency oscillations within and between hippocampi. Whereas the surge in beta power developed at non-lethal chloral hydrate doses, the surge in gamma power was specific for impending death. In contrast, CH strongly suppressed theta band power in both CA1 and CA3 and reduced inter-regional coherence in the theta band. The simultaneously recorded electrocardiogram showed a small decrease in heart rate but no change in waveform during the high-frequency oscillation surge, with cardiac arrest only developing after the cessation of breathing and collapse of all oscillatory activity. These results demonstrate that the high-frequency oscillation surge just before death is not limited to cardiac arrest and that especially the increase in gamma synchronization in CA1 may contribute to NDE observed both with and without cardiac arrest.

Semiology and Mechanisms of Near-Death Experiences

PURPOSE OF REVIEW

Near-death experiences (NDEs) are conscious perceptual experiences, including self-related emotional, spiritual, and mystical experiences, occurring in close encounters with death or in non-life-threatening situations. The origin of NDEs remains unknown. Here, we review recent advances in the understanding of NDE semiology and pathophysiology.

RECENT FINDINGS

Recent prospective studies confirm that NDEs reflect a spectrum of highly distinctive memories which are associated with negative or positive emotions and can be influenced by the nature of the causal event, but the temporal sequence with which these images unfold is variable. Some drugs, notably ketamine, may lead to experiences that are similar or even identical to NDEs. New models extend previous neural network theories and include aspects of evolutionary and quantum theories. Although the factual existence of NDEs is no longer doubted and the semiology well-described, a pathophysiological model that includes all aspects of NDEs is still lacking.

Approach to cardiopulmonary resuscitation induced consciousness, an emergency medicine perspective

BACKGROUND

Cardiopulmonary resuscitation (CPR) remains the key intervention following cardiac arrest because of its ability to continue circulation. Recent focus on high quality compressions during CPR has coincided with more frequent encounters of CPR Induced Consciousness (CPRIC). CPRIC represents a poorly understood patient experience during CPR and defined as signs of consciousness and pain perception during CPR.

METHODS

Articles were selected using PubMed, MEDLINE, CINAHL and Scopus search for the keywords "cardiopulmonary resuscitation", "consciousness", "awareness", "resuscitation", "cardio-cerebral resuscitation", "agitation" and "patient experience" yielding 336 articles. Results and their references were assessed for relevance. Articles were filtered by English language and the keyword. Case reports and case series were included. All remaining articles were reviewed and findings were discussed.

RESULTS

A total of ten articles were selected, which included data on 123 cases. Sample size varied per study from 1 to 112. Studies included cases of out-of-hospital cardiac arrest and in hospital cardiac arrest. Compressions were manually provided in most cases. Patient total recall was reported in 40% of cases. Use of sedation was reported in 40% of cases.

CONCLUSIONS

There is need for continued research to better describe, explain and manage the phenomena of CPRIC. From the articles reviewed here, it is clear that further investigation has the potential to properly elucidate the patient experience including lasting psychological effects of CPRIC. Importantly, there is need for more than recognition of CPRIC from national authorities. Future research efforts should focus on establishing guidelines for the use of sedation and physical restraints, as well as the potential impact of treating CPRIC on survival.

Neurochemical models of near-death experiences: A large-scale study based on the semantic similarity of written reports

The real or perceived proximity to death often results in a non-ordinary state of consciousness characterized by phenomenological features such as the perception of leaving the body boundaries, feelings of peace, bliss and timelessness, life review, the sensation of traveling through a tunnel and an irreversible threshold. Near-death experiences (NDEs) are comparable among individuals of different cultures, suggesting an underlying neurobiological mechanism. Anecdotal accounts of the similarity between NDEs and certain drug-induced altered states of consciousness prompted us to perform a large-scale comparative analysis of these experiences. After assessing the semantic similarity between ≈15,000 reports linked to the use of 165 psychoactive substances and 625 NDE narratives, we determined that the N-methyl-D-aspartate (NMDA) receptor antagonist ketamine consistently resulted in reports most similar to those associated with NDEs. Ketamine was followed by Salvia divinorum (a plant containing a potent and selective κ receptor agonist) and a series of serotonergic psychedelics, including the endogenous serotonin 2A receptor agonist N,N-Dimethyltryptamine (DMT). This similarity was driven by semantic concepts related to consciousness of the self and the environment, but also by those associated with the therapeutic, ceremonial and religious aspects of drug use. Our analysis sheds light on the long-standing link between certain drugs and the experience of "dying", suggests that ketamine could be used as a safe and reversible experimental model for NDE phenomenology, and supports the speculation that endogenous NMDA antagonists with neuroprotective properties may be released in the proximity of death.

Fantasy Proneness Correlates With the Intensity of Near-Death Experience

Little is known about the personality characteristics of those who have experienced a "Near-Death Experience" (NDE). One interesting candidate is fantasy proneness. We studied this trait in individuals who developed NDEs in the presence (i.e., classical NDEs) or absence (i.e., NDEs-like) of a life-threatening situation. We surveyed a total of 228 individuals. From those, 108 qualified as NDE experiencers (i.e., Greyson NDE scale total score ≥7): 51 had their NDEs in the context of a life-threatening situation; 57 had their NDEs not related to a life-threatening situation. From those who did not meet the criteria to be considered "experiencers," 20 had their NDE in the absence of a life-threatening situation; 50 had faced death but did not recall a NDE and finally, 50 were healthy people without a history of life threat and/or NDE. All participants completed a measure of NDE intensity (the Greyson NDE scale) and a measure of fantasy proneness (the Creative Experiences Questionnaire). People reporting NDEs-like scored higher on fantasy proneness than those reporting classical NDEs, individuals whose experiences did not meet the NDE criteria and matched controls. By contrast, individuals reporting classical NDEs did not show different engagement in fantasy as matched controls. The reported intensity of the experiences was positively correlated with engagement in fantasy. Our findings support the view that strong engagement in fantasy by individuals recalling NDEs-like might make these persons more likely to report such subjective experiences when exposed to suitable physiological and/or psychological conditions (e.g., meditation, syncope).

Temporality of Features in Near-Death Experience Narratives

Background: After an occurrence of a Near-Death Experience (NDE), Near-Death Experiencers (NDErs) usually report extremely rich and detailed narratives. Phenomenologically, a NDE can be described as a set of distinguishable features. Some authors have proposed regular patterns of NDEs, however, the actual temporality sequence of NDE core features remains a little explored area.

Objectives: The aim of the present study was to investigate the frequency distribution of these features (globally and according to the position of features in narratives) as well as the most frequently reported temporality sequences of features.

Methods: We collected 154 French freely expressed written NDE narratives (i.e., Greyson NDE scale total score ≥ 7/32). A text analysis was conducted on all narratives in order to infer temporal ordering and frequency distribution of NDE features.

Results: Our analyses highlighted the following most frequently reported sequence of consecutive NDE features: Out-of-Body Experience, Experiencing a tunnel, Seeing a bright light, Feeling of peace. Yet, this sequence was encountered in a very limited number of NDErs.

Conclusion: These findings may suggest that NDEs temporality sequences can vary across NDErs. Exploring associations and relationships among features encountered during NDEs may complete the rigorous definition and scientific comprehension of the phenomenon.

Near-death experiences, posttraumatic growth, and life satisfaction among burn survivors

Survivors of large burns may face positive and negative psychological after-effects from close-to-death injuries. This study is the first to examine their near-death experiences (NDEs) and posttraumatic growth (PTG) and life satisfaction afterwards. With an available sample of 92 burn survivors, half met the criteria for an NDE using an objective scale. Those who indicated religion was a source of strength and comfort had high scores on life satisfaction, PTG, and the NDE Scale. Individuals with larger burns reported greater PTG than those with smaller total body surface area burned (TBSA). There were no significant differences on life satisfaction, PTG, or NDEs when examined by gender or years since the burn injury. Elements of the NDE most frequently reported were: An altered sense of time, a sense of being out of the physical body, a feeling of peace, vivid sensations, and sense of being in an "other worldly" environment. Social workers and other health providers need to be comfortable helping burn survivors discuss any NDEs and process these through survivors' spirituality and religious belief systems as they recover.

Mathematical Modeling of Extinction of Inhomogeneous Populations

Mathematical models of population extinction have a variety of applications in such areas as ecology, paleontology and conservation biology. Here we propose and investigate two types of sub-exponential models of population extinction. Unlike the more traditional exponential models, the life duration of sub-exponential models is finite. In the first model, the population is assumed to be composed of clones that are independent from each other. In the second model, we assume that the size of the population as a whole decreases according to the sub-exponential equation. We then investigate the "unobserved heterogeneity," i.e., the underlying inhomogeneous population model, and calculate the distribution of frequencies of clones for both models. We show that the dynamics of frequencies in the first model is governed by the principle of minimum of Tsallis information loss. In the second model, the notion of "internal population time" is proposed; with respect to the internal time, the dynamics of frequencies is governed by the principle of minimum of Shannon information loss. The results of this analysis show that the principle of minimum of information loss is the underlying law for the evolution of a broad class of models of population extinction. Finally, we propose a possible application of this modeling framework to mechanisms underlying time perception.

Near-Death Experiences in patients with locked-in syndrome: Not always a blissful journey

Memories of Near-Death Experiences (NDEs) most often are recounted as emotionally positive events. At present, no satisfactory explanatory model exists to fully account for the rich phenomenology of NDEs following a severe acute brain injury. The particular population of patients with locked-in syndrome (LIS) provides a unique opportunity to study NDEs following infratentorial brain lesions. We here retrospectively characterized the content of NDEs in 8 patients with LIS caused by an acute brainstem lesion (i.e., "LIS NDEs") and 23 NDE experiencers after coma with supratentorial lesions (i.e., "classical NDEs"). Compared to "classical NDEs", "LIS NDEs" less frequently experienced a feeling of peacefulness or well-being. It could be hypothesized that NDEs containing less positive emotions might have a specific neuroanatomical substrate related to impaired pontine/paralimbic connectivity or alternatively might be related to the emotional distress caused by the presence of conscious awareness in a paralyzed body.

Near-death experiences in non-life-threatening events and coma of different etiologies

Background: Near death experiences (NDEs) are increasingly being reported as a clearly identifiable physiological and psychological reality of clinical significance. However, the definition and causes of the phenomenon as well as the identification of NDE experiencers is still a matter of debate. To date, the most widely used standardized tool to identify and characterize NDEs in research is the Greyson NDE scale. Using this scale, retrospective and prospective studies have been trying to estimate their incidence in various populations but few studies have attempted to associate the experiences' intensity and content to etiology.

Methods: This retrospective investigation assessed the intensity and the most frequently recounted features of self-reported NDEs after a non-life-threatening event (i.e., “NDE-like” experience) or after a pathological coma (i.e., “real NDE”) and according to the etiology of the acute brain insult. We also compared our retrospectively acquired data in anoxic coma with historical data from the published literature on prospective post-anoxic studies using the Greyson NDE scale.

Results: From our 190 reports who met the criteria for NDE (i.e., Greyson NDE scale total score >7/32), intensity (i.e., Greyson NDE scale total score) and content (i.e., Greyson NDE scale features) did not differ between “NDE-like” (n = 50) and “real NDE” (n = 140) groups, nor within the “real NDE” group depending on the cause of coma (anoxic/traumatic/other). The most frequently reported feature was peacefulness (89–93%). Only 2 patients (1%) recounted a negative experience. The overall NDE core features' frequencies were higher in our retrospective anoxic cohort when compared to historical published prospective data.

Conclusions: It appears that “real NDEs” after coma of different etiologies are similar to “NDE-like” experiences occurring after non-life threatening events. Subjects reporting NDEs retrospectively tend to have experienced a different content compared to the prospective experiencers.

Near death experiences: a multidisciplinary hypothesis

Recently, we proposed a novel biophysical concept regarding on the appearance of brilliant lights during near death experiences (NDEs) (Bókkon and Salari, 2012). Specifically, perceiving brilliant light in NDEs has been proposed to arise due to the reperfusion that produces unregulated overproduction of free radicals and energetically excited molecules that can generate a transient enhancement of bioluminescent biophotons in different areas of the brain, including retinotopic visual areas. If this excess of bioluminescent photon emission exceeds a threshold in retinotopic visual areas, this can appear as (phosphene) lights because the brain interprets these intrinsic retinotopic bioluminescent photons as if they originated from the external physical world. Here, we review relevant literature that reported experimental studies (Imaizumi et al., 1984; Suzuki et al., 1985) that essentially support our previously published conception, i.e., that seeing lights in NDEs may be due to the transient enhancement of bioluminescent biophotons. Next, we briefly describe our biophysical visual representation model that may explain brilliant lights experienced during NDEs (by phosphenes as biophotons) and REM sleep associated dream-like intrinsic visual imageries through biophotons in NDEs. Finally, we link our biophysical visual representation notion to self-consciousness that may involve extremely low-energy quantum entanglements. This article is intended to introduce novel concepts for discussion and does not pretend to give the ultimate explanation for the currently unanswerable questions about matter, life and soul; their creation and their interrelationship.

Infrequent near death experiences in severe brain injury survivors - A quantitative and qualitative study

Background:

Near death experiences (NDE) are receiving increasing attention by the scientific community because not only do they provide a glimpse of the complexity of the mind-brain interactions in ‘near-death’ circumstances but also because they have significant and long lasting effects on various psychological aspects of the survivors. The over-all incidence-reports of NDEs in literature have varied widely from a modest Figure of 10% to around 35%, even up to an incredible Figure of 72% in persons who have faced close brush with death. Somewhat similar to this range of difference in incidences are the differences prevalent in the opinions that theorists and researchers harbor around the world for explaining this phenomena. None the less, objective evidences have supported physiological theories the most. A wide range of physiological processes have been targeted for explaining NDEs. These include cerebral anoxia, chemical alterations like hypercapnia, presence of endorphins, ketamine, and serotonin, or abnormal activity of the temporal lobe or the limbic system. In spite of the fact that the physiological theories of NDEs have revolved around the derangements in brain, no study till date has taken up the task of evaluating the experiences of near-death in patients where specific injury has been to brain. Most of them have evaluated NDEs in cardiac-arrest patients. Post-traumatic coma is one such state regarding which the literature seriously lacks any information related to NDEs. Patients recollecting any memory of their post-traumatic coma are valuable assets for NDE researchers and needs special attention.

Materials and Methods:

Our present study was aimed at collecting this valuable information from survivors of severe head injury after a prolonged coma. The study was conducted in the head injury department of Guangdong 999 Brain hospital, Guangzhou, China. Patients included in the study were the ones Recovered from the posttraumatic coma following a severe head injury. A total of 86 patients were chosen. Near death experience scale (NDES) score of 7 or more was used as the criteria of screening NDE experiences. After identifying such individuals, the Prakash-modification of the Interpretative Phenomenological Analysis (IPA) was used to interview and record the data for qualitative analysis.

Results:

We found that contrary to earlier incidence reports, NDEs in post head injury patients were markedly low. Only 3 out of 86 of the patients recruited had a clear and confident experience of NDE. We conducted a qualitative study to explore further into these experiences. IPA of these 3 patients revealed four master themes: 1. Unique light visions 2. Intense feelings of astonishment, pleasure, and fear 3. The sense of helplessness 4. Supernatural but rationality of experience.

Conclusion:

NDE is uncommon in head-injury cases as compared to other near-death conditions. But the persons experiencing it have immense impacts on their belief systems and emotions. This experience should be further explored by studies of larger samples.

Characteristics of near-death experiences memories as compared to real and imagined events memories

Since the dawn of time, Near-Death Experiences (NDEs) have intrigued and, nowadays, are still not fully explained. Since reports of NDEs are proposed to be imagined events, and since memories of imagined events have, on average, fewer phenomenological characteristics than real events memories, we here compared phenomenological characteristics of NDEs reports with memories of imagined and real events. We included three groups of coma survivors (8 patients with NDE as defined by the Greyson NDE scale, 6 patients without NDE but with memories of their coma, 7 patients without memories of their coma) and a group of 18 age-matched healthy volunteers. Five types of memories were assessed using Memory Characteristics Questionnaire (MCQ – Johnson et al., 1988): target memories (NDE for NDE memory group, coma memory for coma memory group, and first childhood memory for no memory and control groups), old and recent real event memories and old and recent imagined event memories. Since NDEs are known to have high emotional content, participants were requested to choose the most emotionally salient memories for both real and imagined recent and old event memories. Results showed that, in NDE memories group, NDE memories have more characteristics than memories of imagined and real events (p<0.02). NDE memories contain more self-referential and emotional information and have better clarity than memories of coma (all ps<0.02). The present study showed that NDE memories contained more characteristics than real event memories and coma memories. Thus, this suggests that they cannot be considered as imagined event memories. On the contrary, their physiological origins could lead them to be really perceived although not lived in the reality. Further work is needed to better understand this phenomenon.

Impact of a near-death experience and religious conversion on the mental health of a criminal: case report and literature review

OBJECTIVE

Near-death experiences have been defined as profound psychological events that may occur to a person while close to death or in a situation of extreme physical or emotional distress. These experiences seem to have an important effect on the patients' mental health and may occur in several situations despite their cultural and religious beliefs.

CASE DESCRIPTION

The present case report describes the positive impact of a near-death experience (Greyson scale > 7) followed by religious conversion on the mental health of a former prisoner.

COMMENTS

Investigation of the role of near-death experiences by the scientific community could shed light on the coping mechanisms and moral/ethical transformations that take place in these individuals.

Near-death experiences between science and prejudice

Science exists to refute dogmas; nevertheless, dogmas may be introduced when undemonstrated scientific axioms lead us to reject facts incompatible with them. Several studies have proposed psychobiological interpretations of near-death experiences (NDEs), claiming that NDEs are a mere byproduct of brain functions gone awry; however, relevant facts incompatible with the ruling physicalist and reductionist stance have been often neglected. The awkward transcendent look of NDEs has deep epistemological implications, which call for: (a) keeping a rigorously neutral position, neither accepting nor refusing anything a priori; and (b) distinguishing facts from speculations and fallacies. Most available psychobiological interpretations remain so far speculations to be demonstrated, while brain disorders and/or drug administration in critical patients yield a well-known delirium in intensive care and anesthesia, the phenomenology of which is different from NDEs. Facts can be only true or false, never paranormal. In this sense, they cannot be refused a priori even when they appear implausible with respect to our current knowledge: any other stance implies the risk of turning knowledge into dogma and the adopted paradigm into a sort of theology.

Hypothesis about brilliant lights by bioluminescent photons in near death experiences

In near death experiences (NDEs), seeing a brilliant light may arise in the recovery period following cardiac arrest, but the subjects can think that these experiences had happened during the actual period itself. Here we hypothesize a biophysical explanation about the encounter with a brilliant light in NDEs. Accordingly, meeting brilliant light in NDEs is due to the reperfusion that induces unregulated overproduction of free radicals and excited biomolecules among them in numerous parts in the visual system. Unregulated free radicals and excited species can produce a transient increase of bioluminescent photons in different areas of the visual system. If this excess of bioluminescent photon emission exceeds a threshold, they can appear as (phosphene) lights in our mind. In other words, seeing a brilliant light in NDEs may due to bioluminescent photons simultaneously generated in the recovery phase of numerous areas of the visual system and the brain interprets these intrinsic bioluminescent photons as if they were originated from the external visual world. Although our biophysical explanation about brilliant light phenomenon in NDEs can be promising, we do not reject further potential notions.

The divided self: near death experiences of resuscitated patients--a review of literature

This paper explores the prevalence of 'near death experience' phenomena associated with a resuscitation event and examines the current state of evidence for causation. Patients' reports of unusual recollections associated with a period of unconsciousness (perceived as approaching death) have fascinated individuals and the medical fraternity. Near death experiences (NDE) are reported in 4-9% of general community members and up to 23% of critical illness patients, although they can occur in healthy individuals who may think they are in peril. One explanation is that paranormal visions that include seeing bright lights, a tunnel and having feelings of peace may be a stage of enlightenment as death approaches. More objective explanations point to neuro-chemical changes in a stressed or dying brain as explanation for nearly all the elements of near death experience. However if this is so, NDE should occur in all patients who are critically ill and near death. In general, patients report positive psychological outcomes after a near death experience. Nurses can support patients during a time of crisis by assisting them and their families to comprehend the experiential event using effective communication and listening skill.

Near-death states reported in a sample of 50 misusers

Increase in recreational ketamine use may be a cause for concern. We aimed here at assessing, in a sample of ketamine misusers, concordance between the typical near-death experience (NDE) features and the on-drug psychoactive effects the subjects experienced. In 2003-2005, a sample of previous ketamine misusers recollecting a ketamine-related NDE were recruited through snowballing and screened with the means of the Greyson NDE Scale; 125 participants made an initial contact with the researcher and 50 reported a minimum score of seven at the "Greyson NDE Scale". Interviewees were in the range 21-66 years old; 27 participants (54%) were educated at BA level, 18 (36%) had an MSc, and 5 (10%) a PhD. Eight (16%) interviewees had a definite religious background. An average lifetime ketamine intake of 140 occasions was reported by the interviewees, who typically presented with a polydrug, including cannabis and MDMA/ecstasy, misuse history. In 45 (90%) cases, the NDE occurred during the first few occasions of intake. Most frequent features of reported NDE states included: altered perception of time (90%), strong sense of detaching from own physical body (88%), and a sense of peace/joy (76% of subjects). Although results here described were elicited from a self-selected, nonrandomized, limited size sample of misusers, we suggest that recreational ketamine intake may be associated with occurrence of near-death related states.

The effect of carbon dioxide on near-death experiences in out-of-hospital cardiac arrest survivors: a prospective observational study

Introduction

Near-death experiences (NDEs) are reported by 11-23% of cardiac arrest survivors. Several theories concerning the mechanisms of NDEs exist - including physical, psychological, and transcendental reasons - but so far none of these has satisfactorily explained this phenomenon. In this study, we investigated the effect of partial pressures of O₂ and CO₂, and serum levels of Na and K on the occurrence of NDEs in out-of-hospital cardiac arrest survivors.

Methods

A prospective observational study was conducted in the three largest hospitals in Slovenia. Fifty-two consecutive patients (median age 53.1 years, 42 males) after out-of-hospital cardiac arrest were included. The presence of NDEs was assessed with a self-administered Greyson's NDE scale. The initial partial pressure of end-tidal CO₂, the arterial blood partial pressures of O₂ and CO₂ and the levels of Na and K in venous blood were analysed and studied. Univariate analyses and multiple regression models were used.

Results

NDEs were reported by 11 (21.2%) of the patients. Patients with higher initial partial pressures of end-tidal CO₂ had significantly more NDEs (P < 0.01). Patients with higher arterial blood partial pressures of CO₂ had significantly more NDEs (P = 0.041). Scores on a NDE scale were positively correlated with partial pressures of CO₂ (P = 0.017) and with serum levels of potassium (P = 0.026). The logistic regression model for the presence of NDEs (P = 0.002) explained 46% of the variance and revealed higher partial pressures of CO₂ to be an independent predictor of NDEs. The linear regression model for a higher score on the NDE scale (P = 0.001) explained 34% of the variance and revealed higher partial pressures of CO₂, higher serum levels of K, and previous NDEs as independent predictors of the NDE score.

Conclusions

Higher concentrations of CO₂ proved significant, and higher serum levels of K might be important in the provoking of NDEs. Since these associations have not been reported before, our study adds novel information to the field of NDEs phenomena.

Equivalência semântica da versão em português da Escala de Experiência de Quase-Morte

Na literatura internacional, a experiência de quase-morte (EQM) é avaliada principalmente por meio do instrumento The Near-Death Experience Scale (NDE), elaborado por Bruce Greyson, em 1983. O objetivo do presente estudo é verificar a existência de equivalência semântica entre a versão original da escala (em inglês) e a versão traduzida ao português do Brasil, avaliando os significados geral e referencial. Após as diversas etapas de avaliação da equivalência semântica, a escala foi pré-testada em seis pacientes internados após alta de um Centro de Tratamento Intensivo (CTI) de um Hospital Universitário. Na avaliação realizada por dois psicólogos e dois psiquiatras, constatou-se existir equivalência semântica entre a versão final em português e o original. Na aplicação da escala na população-alvo, verificou-se boa compreensão dos itens. Portanto, a escala está adequada à cultura brasileira, podendo ser utilizada para pesquisas sobre Experiências de Quase-Morte neste contexto.