Danish doctors are reporting a disturbing case of a man who went into cardiac arrest yet managed to remain awake the whole time doctors attempted to revive him with CPR.

Despite undergoing chest compressions for 90 minutes, the man’s heart failed to restart on its own, and he did not survive.

An autopsy later revealed the man had suffered an aortic dissection, meaning the walls of a major artery in his heart had completely torn, a condition that is almost always fatal.

The doctors say that while awareness during CPR is “extremely rare,” it has been reported in the medical literature before. They say this case and others suggest that there may be a need to provide sedation to patients during CPR.

Dr. Rune Lundsgaard, an anesthesiologist at Herlev Hospital in Copenhagen, presented the man’s case Monday at the Euroanaesthesia congress in Copenhagen.

He said the 69-year-old had gone to the hospital after experiencing three days of what he thought was indigestion. While he was being admitted, his heart suddenly began to race and then stopped completely.

Medical staff immediately began chest compressions and gave him oxygen a mask.  By the time, the CPR team arrived, the man had “a high level of awareness, with open eyes and movement of the head and limbs,” Dr. Lundsgaard wrote.

The medical team continued chest compressions and gave the man several shots of epinephrine (also known as adrenaline), but the man’s heart would not restart.

After one hour, doctors performed an ultrasound of the area around his heart and suspected he had an aortic dissection.

Despite the medical team’s best efforts, they could not get the man’s heart beating again on its own. The team stopped the compressions and the man died.

Lundsgaard noted that deciding to stop the CPR raised serious ethical questions for the medical team, because even though they knew the man was unlikely to survive, “the patient was still conscious once the resuscitation was terminated."

A study published in 2014 found that about two per cent of survivors of cardiac arrest reported experiencing full awareness during CPR. Other CPR survivors had memories of so-called out-of-body experiences, but could not recall them well due to the effects of sedative drugs or brain injury.

That study noted that many CPR survivors went on to experience post-traumatic stress disorder.

Lundsgaard says further attention and research needs to be directed to whether sedation should be given during CPR.

"At this time, we the medical profession are not attending to the pain we cause, nor are we aware about patients' levels of consciousness during CPR. This should be an area of future research,” he concludes.