Cold circulatory arrest in surgery: 3 memories in Montreal and none in Rennes

Step 1

Before the studies · The question

In the operating room, it is known when the blood stops

No one knows exactly how long the brain goes without blood when someone has a cardiac arrest on the street or in the hospital. Doctors arrive, resuscitate and write down what they can.

Some operations are different. Surgeons stop the circulation on purpose, at a time that is recorded and for minutes that are measured. Some researchers thought this operation made it possible to study NDEs with more data.

If these patients described an NDE, it would be much clearer what state their body was in at that moment.

Step 2

The operation · According to the studies

To operate on the aorta, they cool the body and stop the circulation

The aorta is the largest artery in the body. It leaves the heart and carries blood to the whole body. When it tears or widens, a section sometimes has to be replaced.

To sew in that section, surgeons need no blood to flow through it. So they connect the patient to a machine that cools their blood until the body is much colder than normal. Then they stop the circulation for a few minutes. In the cold, the brain uses much less and can go longer without blood.

Doctors call it hypothermic circulatory arrest. On this page we call it cold circulatory arrest.

Pam Reynolds was operated on in 1991 with a similar technique, to remove a bulge in an artery in her brain. Her body temperature was lowered to about 15 degrees Celsius.

Step 4

On reading the questionnaires · According to the letter

3 of the 33 people say their mind was active

Of the 33 people who answered, 3 said they had conscious mental activity during the operation. That is about 9 in 100. The team interviewed them after receiving the questionnaires.

The letter does not say what two of them experienced. It describes only one case, that of a patient it calls J.S.

Step 5

October 26, 2008 · According to the letter

The only case the letter describes: J.S. says she saw a nurse and some machines from outside her body

J.S. was 31 years old and 31 weeks pregnant. After an emergency cesarean section, she had surgery on her aorta with cold circulatory arrest, under general anesthesia and with her eyes taped shut. She said that at some point during the operation she left her body. She also said that she saw a nurse and the machines behind her head. According to the letter, the surgeon who operated on her confirmed that this was accurate.

The letter does not publish J.S.’s words or the surgeon’s. The cold circulatory arrest lasted 15 minutes, and the authors themselves acknowledge that it cannot be known whether J.S. experienced this during the arrest itself. We tell the whole story in J.S.’s story.

The study never measured J.S.’s brain activity.

Step 7

During the operation · According to the study

An arrest of about 27 minutes, at about 24 degrees, under anesthesia

In the 67 operations with arrest, the body was cooled to 23.7 degrees Celsius on average. The circulation was stopped for about 27 minutes on average, though some operations took much less time than others. During the arrest, the patient’s head was packed in ice.

In 21 of those operations, the surgeons kept sending some blood to the brain through a separate tube. In the other 46, the brain received no blood during the arrest.

All patients were under general anesthesia. Before the circulation was stopped, those who were going to have the arrest also received 1,000 milligrams of thiopental, another anesthetic. No anesthetic was given during the arrest.

The operation lasted about 5 hours. Afterward, the patients stayed asleep in the ICU for at least 3 more hours. In total, general anesthesia lasted about 14 hours on average.

Step 8

4 to 9 days later · According to the study

A 15-minute interview on the ward

Once the patient was stable and on the ward, the same doctor always did an interview of about 15 minutes. It took place 4 to 9 days after the operation.

First the doctor asked whether the patient remembered anything from the time they were unconscious, and what. Then the doctor gave them the scale of Bruce Greyson, an American psychiatrist. It has 16 questions, and each thing experienced adds points, for example peace, a light, seeing a relative who had died or leaving the body. With 7 points or more, it counts as an NDE.

Step 9

When the interviews were done · According to the study

None of the 101 people remembers anything

None of the 101 people remembered anything from the time they were unconscious. Neither the 67 who had the cold circulatory arrest nor the 34 who did not remembered anything.

So no one reached 7 points on the scale. In this study there was no NDE.

The authors expected to find some. Between 6 and 12 in 100 people who survive a cardiac arrest describe an NDE, according to other studies. According to the authors, 67 people were enough to find some cases.

Step 10

2021 · According to the study

The authors look for why no one remembers anything

The article was published in 2021 in AORTA, a journal of aortic surgery. The authors suggest several reasons for the result:

• Anesthesia. Anesthetics can make people forget what they experienced, or prevent an NDE from happening.
• The hours without consciousness. There were about 14 on average, because anesthesia lasts so long in this operation.
• The time until the interview. Several days went by, although the authors point out that in another study NDEs were not forgotten over the years.
• The cold. The cold, and whether or not blood reached the brain, may have changed its activity. They did not measure it, so they do not know what state it was in. They also point out that the brain may not need to be shut down for an NDE to happen.

The authors conclude that it is still unknown whether cold circulatory arrest triggers NDEs.