Research

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

Zalika Klemenc-Ketis^1,2*, Janko Kersnik^1,2 and Stefek Grmec^3,4,1,2

• * Corresponding author: Zalika Klemenc-Ketis zalika.klemenc-ketis@uni-mb.si

Author Affiliations

¹ Department of Family Medicine, Medical School, University of Maribor, Slomškov trg 15, 2000 Maribor, Slovenia

² Department of Family Medicine, Medical School, University of Ljubljana, Poljanski nasip 58, 1000 Ljubljana, Slovenia

³ Faculty of Health Sciences, University of Maribor, Zitna ulica 15, 2000 Maribor, Slovenia

⁴ Center for Emergency Medicine, Ljubljanska 5, 2000 Maribor, Slovenia

For all author emails, please log on.

Critical Care 2010, 14:R56 doi:10.1186/cc8952

Published: 8 April 2010

Abstract

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.