Doctors in Paris have written a chilling account of treating mass casualties during the multiple attacks that took place in the city earlier this month.

In Tuesday's online issue of The Lancet, doctors from the Assistance publique-hôpitaux de Paris describe their "civil application of war medicine" to mobilize hospitals, recall staff and release beds to cope with the large influx of wounded people.

A total of 35 surgical teams from 10 hospitals across Paris operated on the most seriously injured continuously through the night of Nov. 13.

"Although emergency physicians have been receiving training in disaster medicine for more than 30 years, never before had such a number of victims been reached and so many wounded been operated on urgently. A new threshold has been crossed," the authors wrote.

The physicians concluded by saying they must remain humble and expect deaths in the upcoming days. So far, they report four deaths or one per cent of the 302 injured patients, including two deaths on arrival at hospital.

Emergency medical services divided medical teams and the fire brigade between the sites and kept some in reserve to avoid focusing all resources on the first crisis site and leaving a shortage for other sites.

Since the wounds were mainly bullet related, the strategy focused on doing the fastest possible surgery to those wounds to maintain blood pressure. Demand for tourniquets was so high that mobile teams came back without their belts.

The authors said emergency services participated in a simulation exercise on the morning of the attacks, and that the training was a key factor in the success of treatment.

People line up to give blood at the Saint Louis Hospital in Paris on Nov. 14, a day after the attacks. Maintaining blood pressure for those with bullet wounds was a key part of the emergency medical response. (Jerome Delay/Associated Press)

One of the challenges was that during the long periods of shooting, the streets surrounding the attacks were dangerous for emergency intervention teams.

An anesthesiologist described how one of the civilian trauma centres with a routine capacity of two operating rooms was able to open 10 operating rooms and treat injured patients by calling in all staff.

Professionalism was present at every level, the authors said.

"If I had to summarize the 'winning formula' in the recent tragic hours that we lived in an orthopedic centre … I would say that spontaneity and professionalism were the key ingredients."

By the next day when medical staff reviewed what they'd done, the common observation was all but one of the patients was less than 40 years old.