Strip and shower? Or just strip? Decontamination after a chemical attack
January 29, 2010, 2:13 pm
Chemical Agent Simulant Release from Clothing Following Vapor Exposure. Feldman RJ. Acad Emerg Med Feb 2010;17:221-224.
After the nerve agent sarin was released into the Tokyo subway system in 1995, the hospital closest to the event (St. Luke’s) received hundreds of patients into its emergency department. Although only a few of these patients were critically ill, many others had been exposed to small amounts of sarin vapor and were symptomatic (eye pain, dim vision, lacrimation) but not severely contaminated. As large numbers of patients were brought into the hospital building without any form of decontamination, off-gassing of sarin vapor from their clothing built up and members of the hospital staff became symptomatic with mild but distressing manifestations of early sarin poisoning.
St. Luke’s and its staff did an impressive and heroic job of coping with an unprecedented mass-casualty event involving chemical contamination. One the lessons that came out of this experience was the importance of decontaminating victims in such an event. But what level of decontamination is feasible and appropriate? Some commentators recommend “wet” decontamination of all victims — in essence, having them strip and go through a mass shower. The limitations of this suggestion — expense, logistics, weather, modesty — are obvious. Others suggest that in these events the vast majority of patients who could walk through a shower and have no obvious liquid or particle contamination have been exposed only to chemical vapor — if they have been exposed to any toxin at all. In this case, if they have to be seen in the emergency department, simply having them remove and bag their clothes would accomplish adequate decon. In retrospect, it is apparent that many of the patients who walked into St. Luke’s Hospital would have been better handled at some peripheral location, and did not need to enter the emergency department at all.
In this paper, the author — from Cook County-Stroger Hospital in Chicago — used methyl salicylate vapor to simulate a chemical weapon agent. After exposing various types of clothing to the vapor, he measured the amount and time course of methyl salichylate off-gassing from the garments. He found that light cotton (t-shirts, jeans) had the least trapped vapor, and down outerwear the most. Similarly, the mean time to zero off-gassing ranged form 7 minutes (light cotton) to 42 minutes for down jackets. As the author points out, while this study gives a reasonable comparison of the amount of vapor trapped by various materials, the specific results do not necessarily represent what happens when this clothing is actually worn by individuals. However, I completely agree with the following comment he makes: “It seems unlikely that, by the time mass decontamination can be set up and started, even ast the scene of the exposure, patients who appear well and have no evidence of liquid contamination will still require showering.”
Note: I have not previously seen the clip embedded above, and am not absolutely certain whether it is actual footage of the Tokyo sarin event, or a re-enactment. However, it looks real, and is consistent with confirmed video I have seen of St. Luke’s on the morning of March 20, 1995. Scenes from the hospital start at about 03:15.
precordialthump Says:
Hi Leon,
It’s an interesting dilemma in a mass casualty scenario – one I haven’t had to face (yet). I think that the view provided by you and Feldman is pragmatic and likely to prevent a massive waste of resources as well as allowing care to be focused on the truly sick.
Probably also a good time to emphasize that unlike sarin, the vapors from organophosphate pesticide poisonings are just the solvents and non-lethal – despite the hysteria that can sometimes be created.
Cheers,
Chris
PS.
BTW, are you sure that footage isn’t from the great homeopathic vapor subway poisoning that occurred in Pyongyang circa 1982? There appeared to be a few UCEM officials on the scene wearing gas masks…
January 29th, 2010
Leon Says:
Chris:
Yes, even as a pure thought experiment, I’ve never been able to envision how a mass shower would work as planned, or to imagine a victim who was able to strip and walk through the shower on command, yet had been contaminated with enough of a nasty chemical agent to make wet decon mandatory. In these situations, I firmly believe that the most important goals are to keep as many people as possible out of the acute care area, and to remove the clothing of those contaminated enough to require emergency evaluation and treatment.
Of course, in homeopathic poisoning, where we’re dealing with the memory of water and dilution just seems to increase effect, all bets are off . . .
Leon
January 30th, 2010
wench Says:
I took an NBC class in the Army some years ago – they recommended setting up an external area where you could control entry and exit, designating the entry area “dirty” and the exit area “clean”, and processing people between the two areas. You need to consider runoff from your washing equipment when designing the area. Aside from that, it’s pretty basic theory, and you can process a lot of people fairly quickly with a small team – one crowd control person on entry, one on exit, one or two doing decon. You can have people strip at any point before they enter the water, which can be as simple as a garden hose if you don’t have anything better to use.
This setup can work even on cases with injuries, to ensure medical personnel aren’t exposed so they can maintain their ability to function. if you have EMT personnel who have been handling injured contaminated people they’re going to need to go through the decon area as well. So you get at least two teams of EMT personnel – a “dirty” team who work on the injured on one side of the mess and a “clean” team who get the patients passed on to them through the decon center.
It seems pretty straightforward, but you want your emergency personnel trained so they remember to react the right way when they’re surrounded by enough screaming people to require this sort of set-up.
January 31st, 2010
Leon Says:
I think it’s important to make two distinctions. One is between what is necessary and feasible in the military, and what is possible in the civilian realm. The military is much more likely to have to deal with a chemical incident, and have the resources and manpower to train for such an event. In my opinion, this is extremely difficult outside the military. The second distinction is between what it needed in the “hot zone” — the site of chemical release — and adequate decontamination at receiving hospitals. Most victims who can walk away from the hot zone will certainly do so before showers can be set up. Those who can walk into a receiving hospital are very unlikely to be contaminated with significant amounts of a toxic liquid. There, vapor decon — that is, removal and bagging of clothing — should suffice in almost any conceivable situation. As I mentioned in the post, those who are asymptomatic or minimally symptomatic probably don’t need to enter the hospital at all.
February 1st, 2010
S. Mann Says:
I agree. Everyone needs to strip, but only those with liquid contamination need a full shower. In this way the intake procedure will be cleantake, i.e. everyone goes in clean without taking any contamination (or contraband) with them (remember that some of the “victims” may be perpetrators, so cleantake has the added advantage of making sure no weapons or other contraband get into the hospital).
To implement this you simply need large gender-segregated intake areas where people can leave behind their clothes and enter to receive hospital gowns.
February 22nd, 2010
Leon Says:
Thanks for the comment! I’m not quite sure everyone needs to strip. Even if potentially exposed to a nasty agent such as sarin if the possible contamination involves just vapor, and the person is asymptomatic, one can expect they would not deteriorate once removed from the hot zone around the site of release. Having all people who present to hospital strip, gown, and come into the emergency department risks overloading space and resources needed for victims who are actually sick. What must be avoided is concentrating and large number of people with possible minor vapor contamination in an enclosed poorly ventilated place, where vapor off-gassed from their clothing could build up. Such individuals ideally could be monitored in an outdoor area, weather permitting. I agree that just undressing patients who enter the emergency room should be sufficient in most cases, without wet decon.
February 22nd, 2010