April 3, 2019 -- The 12 boys rescued from deep within a flooded cave in Thailand last July were pulled out as they slept under anesthesia, a strategy that was kept secret at the time because it was risky, according to doctors involved.

The divers who ferried the boys to safety were taught how to give intramuscular injections of the drug ketamine, a short-acting anesthetic, to render them unconscious during the 6-hour trip to the cave entrance. They were also dosed with the anti-anxiety medication Xanax and the drug atropine, which keeps your heart rate steady and prevents muscle spasms.

New details of the rescue emerged on Wednesday in a letter published in the New England Journal of Medicine.

“If the children wake up and panic, it was dangerous too much for the children and the cave diver,” said Chanrit Lawthaweesawat, MD, in an interview. He is the deputy secretary general of the Medical Association of Thailand in Bangkok. He is also an anesthesiologist at Bumrungrad International Hospital

Putting the boys to sleep was also to prevent “psychic trauma” after their ordeal, he said.

The drug ketamine was chosen because it allowed the boys to continue to breathe on their own and kept their blood pressure stable, according to Richard Harris, MD, an anesthesiologist who heads the Retrieval Coordination SAAS MedSTAR Emergency Medical Retrieval in Australia. Harris devised the protocol, according to the medical team.

But using ketamine was risky, too, because the drug decreases shivering, the body’s natural defense mechanism against the cold.

Wilderness rescue experts have wondered exactly how the boys, who reportedly could not swim, were brought out of the cave, an exit that required advanced diving skills. Indeed, one member of the rescue team, a former Thai Navy SEAL, died in one of the underwater passages that were narrow channels filled with fast-flowing cold water.

“How they did this was a national secret or something,” said Gordon Giesbrecht, PhD, who runs the laboratory for exercise and environmental medicine at the University of Manitoba, in Canada.

Watching a presentation on the rescue at a recent medical conference, Giesbrecht remembers thinking, “How did you train these kids to do the dive?”

“There’s a very high chance of panicking and dying. Of course, the explanation [for the rescue plan] makes perfect sense,” said Giesbrecht, who’s also an expert on hypothermia. “It’s brilliant.”

With oxygen levels falling and more rain forecast, doctors knew they were running out of time to save the team and their soccer coach.

2 Weeks in a Cave

The team, known as the Wild Boars, became trapped on June 23 after the cave system they were exploring flooded during a rainstorm and cut off their exit route. It would take more than 2 weeks to get them out.

After they ran out of food, the boys reportedly licked condensation off the limestone walls to survive.

The massive effort to save them captivated the world. It involved thousands of volunteers, including 50 to 60 doctors and dozens of other medical personnel.

After the boys were put to sleep, they were placed on flexible plastic stretchers called Skeds.

They were brought out in three phases, according to Lawthaweesawat, with medical professionals checking on them along the way. One of the longest stretches required the boys to be under water for nearly 2 hours.

Unconscious and unable to shiver, the boys were at risk of hypothermia, a dangerous drop in body temperature. They were also at risk of a phenomenon known as circum-rescue collapse. When the body is submerged, water pressure compresses large blood vessels in the legs, helping send blood to the core. When the body comes out of the water, the drop in pressure reduces the flow of blood, the cold heart and blood vessels don't function as well, and shock happens. The heart can stop and blood pressure drops.

Ketamine helped to offset this deadly drop in blood pressure by constricting the blood vessels, Harris said.

Post-Rescue Recovery

On the first day of the rescue, one of the boys initially did well but became mildly hypothermic on the way to the hospital, Lawthaweesawat said.

Alarmed, the doctors established a three-stage protocol to improve their coordination. In the first stage, a team stood by to carefully remove the wetsuits from the floppy sleeping children, who ranged in age from 11 to 16.

“It was like when you change the Formula 1 wheel,” Lawthaweesawat said. “It was teamwork. The team practiced so they could minimize the time for removal. It was seconds.”

In the second stage, doctors piled the boys with blankets, including a heated blanket, and wrapped them in foil to keep them warm. They used blow dryers to warm any exposed skin. And because saline solution at room temperature can cool the body, the doctors rehydrated the boys with warmed saline.

They checked their temperatures every five minutes on the way to the hospital.

In the end, just two of the 12 boys developed hypothermia, something Giesbrecht said was a great result.

‘Brilliant’ Decision to Keep Quiet

He said he also didn’t blame the doctors for keeping this detail about the anesthesia out of the public eye.

“I wouldn’t have told the media, either,” Giesbrecht said. “They would have said, ‘Oh, you can’t do that.' But they also aren’t mothers and fathers at home frantic to get your children back alive.”

The medical team said they’re sharing their methods now in case they are needed by others in the future.

“The Thai cave rescue mission, the decision to bring the children out with the ketamine-based anesthesia protocol, had pros and cons. But the experts made the agreement that we should use this technique,” Lawthaweesawat said.

He noted that all the boys are fine, with no lingering impacts from their ordeal.

Show Sources

Maj. Chanrit Lawthaweesawat, MD, deputy secretary general, The Medical Association of Thailand, Bangkok.

Richard Harris, MD, BMBS, head of unit, Retrieval Coordination SAAS MedSTAR Emergency Medical Retrieval, Australia.

Maj. Gen. Wutichai Isara, MD, director, Fort Somdej Phranaresuan Maharaj Hospital, Phitsanulok, Thailand.

Krit Pongpirul, MD, PhD, MPH, assistant professor, faculty of Medicine, Chulalongkorn University, Bangkok; Research & Quality Counselor, Bumrungrad International Hospital, Bangkok; Johns Hopkins Bloomberg School of Public Health, Baltimore.

Gordon Giesbrecht, PhD, professor, exercise and environmental medicine, University of Manitoba, Canada.

New England Journal of Medicine, April 4, 2019.

Wilderness Medical Society: “Practice Guidelines for Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia: 2014 Update.”

MedicineNet.com: “Atropine (Atreza).”

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