A study has pointed out that victims who report "near-death experiences," such as flashing lights, experience of joy and peace before they 'come back to earth' may just have elevated levels of carbon dioxide (Co2) in the blood.
Near-death experiences (NDEs) are reported by between 11 and 23 percent of survivors of heart attacks, according to previous research.
But what causes NDEs is strongly debated. Some pin the mechanisms on physical or psychological reasons, while others see a transcendental force.
Researchers in Slovenia, reporting on Thursday in a peer-reviewed journal, Critical Care, investigated 52 consecutive cases of heart attacks in three large hospitals.
The patients' average age was 53 years. Forty-two of them were men.
Eleven patients had NDEs, but there was no common link between these cases in terms of age, sex, level of education, religious belief, fear of death, time to recovery or the drugs that were administered to resuscitate them.
Instead, a common association was high levels of CO2 in the blood and, to a lesser degree, of potassium.
Further work is needed to confirm the findings among a larger sample of patients, say the authors, led by Zalika Klemenc-Ketis of the University of Maribor.
Having an NDE can be a life-changing experience, so understanding its causes is important for heart-attack survivors, they say.