A cat scan revealed that Reynolds had a large artery aneurysm in her brain, close to the brain stem. Because of the difficult position of the aneurysm Dr. Robert Spetzler of the Barrow Neurological Institute in Phoenix, Arizona decided that an unusual surgical procedure, hypothermic cardiac arrest, had to be performed. During this procedure, also known as standstill, her body temperature was lowered to 60 °F (16 °C), her breathing and heartbeat were stopped and the blood was drained from her head. Her eyes were closed with tape. Small ear plugs with speakers were plugged in her ears. These speakers emitted audible clicks which were used to check the function of the brain stem.
For a brief period in the middle of the procedure, she had a flat EEG, a non-responsive brain stem and no blood in her brain. The operation was a success and Reynolds recovered completely.
During the operation but prior to her being put in cardiac arrest, Reynolds later reports hearing a sound like a natural 'D'. The sound seems to pull her out of her body. Then she is floating around in the operating room and watches the doctors performing the operation. She feels more aware than normal and her vision is more focused and clearer than normal vision. She makes several observations, for example:
She notices the doctor using a drill to open her skull. It surprises her that it looks like an electric toothbrush, not like a saw as she expects. It is later confirmed that the drill used by the doctor was similar in appearance to an electric toothbrush.
She hears a female voice say, "We have a problem. Her arteries are too small." It is later confirmed that the doctors first tried to connect the heart-lung machine to the right leg. But the arteries are too small so they switch to the left leg.
These examples appear to show that she was able to see and hear during the operation.
At some point during the operation she notices a presence. Then she is pulled towards a light. As she gets closer the light becomes very bright. She begins to discern figures in the light, including her grandmother, an uncle, other deceased relatives and people unknown to her.
The longer she is there, the more she is enjoying it. But at some point in time she is reminded that she has to go back. Her uncle brings her back to her body. When she looks at her body she doesn't want to go back in. Her uncle tries to persuade her, but she keeps refusing. Then she sees her body making a jump (caused by the defibrillation to start up her heart). Her uncle gives her a push and she is back in her body.
The 'Pam Reynolds' case is on Wikipedia.. if ye want to check it out....