Barbara Howard: Las Vegas hospitals were flooded last night with hundreds of victims of the shooting on the city's strip coming in. Doctors and nurses scrambling to save lives after some were shot, others had broken limbs or were trampled. With us in the studio is Dr. David King. He is someone with similar experience working under pressure with scores of patients in dire need of immediate help. Dr. King is a trauma surgeon at Massachusetts General Hospital. He was at the Mass General operating room four years ago, he was treating victims of the Boston Marathon bombing. Thanks for coming in Dr. King.

King: Of course. My pleasure.

Howard: First let's stipulate that what happened in Boston and Las Vegas were different. Rescue crews could get to the victims in Boston right away, while that was not the case so much in Las Vegas. Plus the numbers last night, they were staggering: over 500 injured showing up in Las Vegas emergency rooms last night. So for a mass casualty event like this, tell us how hospitals even begin to cope with such a huge influx of victims.

King: Well the coping with mass number of casualties starts long before patients get to the hospital. In the United States, we're not entirely sure how to affect the best response right now. For example, it's unclear if we should be providing medical care in the hot zone, that is, before the zone is absolutely cleared of all danger. Should we be providing medical care only in the green zone, so that is, evacuating patients from the hot zone to a zone we know is positively safe. Or is there some intermediate area — should we be providing care and triage in the so-called orange zone or the transitional zone.

Every municipality deals with these scenarios differently. Nobody has the right answer yet probably because there isn't a right answer. But the care of the injured starts the moment the first responder lays eyes on and that care is continuous from that point of injury all the way to and including and past the hospital stay.

Howard: And there's a lot of training, I'm sure, emergency training going into this at this point.

King: Sadly, in the United States we have been forced to create plans and deal with these kinds of scenarios much too often. And that has resulted in an infrastructure that is prepared to deal with this.

Howard: As we mentioned, you were in the operating room on the day of the Boston Marathon bombing back in 2013. In fact, you run the marathon, I understand.

King: That's correct.

Howard: And you rushed to the hospital to scrub in once news of the bombing broke. Were there lessons to be learned from that day?

King: Oh, there certainly were. There's always lessons to be learned from any mass casualty incident, and it's incumbent upon first responders — it's incumbent upon all of us to critically examine all of these events afterwards and try to determine, you know, what we absolutely did right, what we can do better, maybe some mistakes that we made and that kind of introspection is what makes responding to each of these subsequent events better than it was the last time. It's our responsibility, once the dust has settled, to look back and try to determine the best pathway forward for the next one. It's an unfortunate, sad reality that in the world we live in currently, there will likely be a next one.

Howard: Well, aside from your work at Mass General, you also treated U.S. troops who've been wounded in battle in Afghanistan and Iraq. So you have military experience. How fair is it to ask civilian workers, nurses and doctors who've never been in the military setting to do this kind of work in the field?

King: Well, it depends where the work is being done. So the military lessons of war, medical military lessons of war, have absolutely been translated to almost every civilian trauma center in the United States.

Howard: Are the workers psychologically prepared to put themselves without military training in these situations?

King: That is a very interesting question. That gets to what we call the so-called second victim. Compassionate caring providers who are asked to do something they've not done before, perhaps not even conceived of doing so without forethought, and you put them in this kind of dynamic extremely stressful environment, and they may perform admirably throughout the acute event, but the decompression afterwards can be very problematic. And all the medical personnel and allied medical personnel need to be aware that they can suffer effects.

Howard: Like post-traumatic stress?

King: Post-traumatic stress, stress in general, adjustment disorders. And we identify that as the so-called second victim, because these people who are giving every ounce of themselves to the care of the injured right now, that may not be for free for them.

Howard: OK. Thank you so much for joining us Dr. King.

King: My pleasure.

Howard: That's Dr. David King of Massachusetts General Hospital.