A 34-year-old British hiker has been revived in Spain after a six-hour cardiac arrest brought on by severe hypothermia, with the low mountain temperatures that made her ill also helping to save her life.

Key points: Audrey Schoeman had no vital signs when she reached hospital after her body temperature dropped into the teens

Audrey Schoeman had no vital signs when she reached hospital after her body temperature dropped into the teens Six hours after emergency services were contacted, her heart was shocked back into action

Six hours after emergency services were contacted, her heart was shocked back into action Hypothermia actually protected her body and brain from deteriorating, according to her doctor

Audrey Schoeman's ordeal began on November 3 when she and her husband were hiking in the Catalan Pyrenees. As the weather took a turn for the worse, Ms Schoeman, who lives in Barcelona, began experiencing trouble speaking and moving.

The doctors at Barcelona's Vall d'Hebron Hospital said she had suffered the longest documented cardiac arrest in Spain.

"It's an exceptional case in the world," Dr Eduard Argudo told reporters.

She said she had no memory of those six hours.

"Amazing. It's like a miracle except that it's all because of the doctors," Ms Schoeman told Catalan broadcaster TV3.

As the time passed on the mountain, Ms Schoeman fell unconscious and husband Rohan Schoeman told TV3 he thought she was dead.

"I was trying to feel a pulse — I couldn't feel a breath, I couldn't feel a heartbeat," Mr Schoeman said.

By the time rescuers reached the couple two hours later, Ms Schoeman's body temperature had dropped to 18 degrees Celsius and when she reached the hospital, she had no vital signs.

"She looked as though she was dead," Dr Argudo added in a statement.

"But we knew that, in the context of hypothermia, Audrey had a chance of surviving."

Hypothermia, while also bringing her to the brink of death, had protected her body and brain from deteriorating, Dr Argudo said.

Racing against time, doctors turned to a specialised machine capable of removing blood, infusing it with oxygen and reintroducing it to the patient.

Once Ms Schoeman's temperature had reached 30C, doctors turned to the defibrillator. Her heart jumped back into action, some six hours after emergency services were first contacted.

Twelve days later she was released from hospital, nearly fully recovered and with only lingering issues in the mobility and sensitivity of her hands due to the hypothermia.

"We were very worried about any neurological damage," Dr Argudo said.

"Given there are practically no cases of people who have had their heart stop for so long and been revived."

Ms Schoeman said she hoped to be back hiking by the spring.

"I don't want this to take away this hobby from me," she said.

Reuters