*** Suspension Trauma - Serious Risk to Subject *** From: Rob Thomas [ROBERT@medinfo.iplan.co.za] Sent: Monday, September 27, 1999 12:15 AM To: sar-l@listserv.islandnet.com; wilderness-emergency-medicine@list.pitt.edu Subject: Suspension trauma and stretchers Hi all, Apologies for the cross-post for those who receive this more than once, but I think it applies to all lists to which it has been posted. A short while ago someone pointed me to a couple of web-pages relating to suspension trauma, also known as harness induced pathology. What I've written here is a paraphrasing of a couple of articles, some of which are grammatically interesting translations from French. The original source of the info available on the net (and there isn't a great deal of it) appears to be the French caving publication 'Speleo'. This presents a problem to me since I (a) don't receive the magazine and (b) have a pathetic understanding of french anyway. However, I did manage to dig out three articles (two were pointed out to me, the web-bots found the third) dealing with this problem. What happened is this: The French troglodytes had a rash of fatalities (15) on rope in a rather short space of time. Initially these were attributed to overly fatigued cavers attempting longs ascents at the end of rather demanding caving trips and succumbing to fatigue and then hypothermia during the ascent. However, someone with an enquiring mind, access to the right facilities and a fair amount of time on their hands decided to see if this could be reproduced and the progression studied (that 'someone' being the Medical Commission of the French Federation for Speleology). What they found was more than a little disturbing. Prior tests had taken place earlier on (1980's). Two healthy, fit volunteers were suspended in their harnesses and simulated unconsciousness (they went totally inert). They both gave the experimental team a bit of a jolt when they developed some somewhat disturbing troubles and both of them fainted - one after only 6 minutes. Accompanying this loss of consciousness was a radical change in cardiac rhythms. These tests were rather abruptly abandoned as being too dangerous to continue with for fear of losing a perfectly healthy lab-rat. However, they did conclude that without muscular movements, a perfectly healthy person could end up a candidate for a wooden overcoat in a *very* short space of time. A second set of experiments was carried out more recently (early 1990's), this time in a hospital setting under medical supervision and monitoring. Three test scenarios were used: - The first volunteer was in a "real" situation, that is to say with his head in hyper-extension, his legs dangling under heart level. - The second volunteer was wearing a brace in order to exclude the head hyper-extension factor and - the third volunteer had his legs in a high position and his head in hyper-extension. In all three scenarios the volunteers had developed some rather disturbing problems withing 12-15 minutes and again one of them fainted, depite full medical control and supervision. Without going into too much detail, the cause of all this was that in the inert body, the blood tended to pool in the limbs and the head received an inadequate blood supply, resulting in fainting. Now, when someone is standing around and they pass out they fall over, thus neatly correcting the problem of getting blood to the head. However, when suspended in a harness this doesn't necessarily automatically occur, so the problem persists and ultimately ends in death. They decided that any attempt at designing a harness to correct this effect would be futile and that time and money should rather be spent on educating cavers about the cause and effect of this scenario. The advice which follows is this: - A person in difficulty on a rope due to exhaustion or to technical problems must be helped very quickly. - A person hanging in complete inertness must be unhooked VERY URGENTLY by other team members - if not he'll be dead within about 30 minutes. - A team shall never let ONE of its members start alone a rope ascent, even if he is in very good health condition. - A tired speleologist should refuse to begin a long and difficult rope ascent, especially in a wet hole, without recovering first. He must carry with him and use at the proper time his survival food and cover. So, I started doing a little thinking (unusual for me) and came up with a parallel for the SAR world. I also came up with a second parallel which supports the first to some extent and I'd appreciate other people's views on the matter. When a patient is packaged in a stretcher and fully immobilised, they are essentially inert. Add to this a possible reduced level of consciousness and the inert state is even more complete. Now take this person and place them in a vertical haul scenario. Would they not suffer precisely the same effects? The parallel I came up with seems a little loose but I think it substantiates my point somewhat. Those of you who have had the (mis)fortune to spend time in any of the armed forces will probably have done your fair share of parades. For those of you who haven't, there's a particular event during parades which turns out to be quite unpleasant: the time when the head honcho gets to make a speech. The length of the speech is proportional to (a) the importance of the parade and (b) the importance of the speaker. During this time the souls on the parade ground are expected to stand extremely still. They too, like the person hanging in a harness or a patient in a vertically-hauled stretcher, are inert in a vertical position. The only difference here is that they use their legs and feet to maintain their balance so they have small amounts of muscular movement in their legs. However, some of them still faint - occasionally quite spectacularly. Herein lies the difference: their fainting very neatly self-corrects the problem because they end up horizontal (although occasionally with entertaining facial/dental injuries). The person in the stretcher, on the other hand, remains upright throughout the process, thus emulating the person in the harness. We've experienced this in our team during training with one of the team members in a Skedco Sked stretcher during a vertical haul. He started changing colour and feeling faint after 8 or 10 minutes of vertical haul. A nearly group of cavers has experienced similar problems, also during a practise with a team member in a Skedco Sked stretcher. This makes me wonder whether the Sked contributes to the problem at all. However, it also made us realise that we should choose a horizontally orientated stretcher for all hauls if at all possible and that we should spend as much time as necessary getting our patient into a more robust state before attempting evacuation, especially if there's a possibility that we may need to go vertical at any point. Anyone else experienced this? Any comments / ideas? Regards Rob Thomas +27-12 450-2957 07h30-16h30 GMT+0200 +27-82-652-2540 all hours (try to be reasonable) 27 Sep 99, at 9:15, Rob Thomas wrote: A short while ago someone pointed me to a couple of web-pages relating to suspension trauma, also known as harness induced pathology. What I've written here is a paraphrasing of a couple of articles, some of which are grammatically interesting translations from French. Hi, Rob. Your post and subsequent posts are indeed a nice summary of the problem and the "literature" such as it is. A standard first-year medical school physiology experiment is to place a student on a "tilt-table" and tilt the student head-up without letting him or her stand. The other students check the blood pressure and pulse and are very surprised when the student on the table gets, essentially, shocky. So the physiology is a no-brainer. A harness may indeed make the situation worse by constricting the bloodflow some more. A padded harness may make this a bit less of a problem, but you're right, the main problem is the lack of muscular pumping action pushing venous blood back up the legs. (It might be worth noting the anatomy: every inch or few along the larger veins in the legs are oneway valves. With muscular contractions alternately compressing different segments of the vein, this works like a wonderful pump to return venous blood to the torso-- but it depends on strong and continuously changing muscular contractions squeezing the sections of vein between the valves. However, we know that people who are tired tend to be dehydrated, too. And, we also know that cold stress, even without true hypothermia, causes significant dehydration ("cold diuresis"). So, take someone who is really cold, really tired and dehydrated, and put him or her vertically on a rope with something tied around the proximal thighs (a venous tourniquet, AKA a seat harness) you have a recipe for disaster. And, given the observation about medical-student tilt-table experiments, it's certainly true this is a problem for litter patients, too. I will make an observation about a great article: Pugh LGCE. Hypothermia in walkers, climbers, and campers: report to the medical commission on accident prevention. Br Med J 1966; 123-129 One of the first medical reports on hypothermia (and BTW a wonderful description of how not to run a backcountry run/walk), this paper describes one patient who was hypothermic and probably dehydrated -- and as soon as tilted head-up in the litter, seized and died. In the WEMSI Wilderness EMT course we teach that dehydrated/hypothermic patients should NOT be tilted in the headup position if at all possible -- and if you have to tilt such a patient, i.e. to get up a narrow pit in a cave -- rehydrate first, and consider putting the MAST garment on the patient, inflation prior to the vertical lift, and deflating after the vertical portion's done. BTW, I do know that there is an international society for fall prevention, dealing with workers on scaffolds and window washers and the like, and suspect that there is more information about "harness hang" out there but haven't had the time to dig further and see if there's any information there. Take care. --Keith Conover, M.D., FACEP http://www.pitt.edu/~kconover Hal Lillywhite [hall@mxim.com] Keith Conover, M.D., FACEP writes: A standard first-year medical school physiology experiment is to place a student on a "tilt-table" and tilt the student head-up without letting him or her stand. The other students check the blood pressure and pulse and are very surprised when the student on the table gets, essentially, shocky. So the physiology is a no-brainer. One of the first medical reports on hypothermia (and BTW a wonderful description of how not to run a backcountry run/walk), this paper describes one patient who was hypothermic and probably dehydrated -- and as soon as tilted head-up in the litter, seized and died. Timely information from my point of view. Our group was looking into going mainly to a vertical position raise or lowering for injured subjects. The idea was that we can do this so much faster than when the patient is horizontal that we thought a short time vertical would beat a much longer time horizontal while getting the patient to a place where we can provide better care. This obviously throws doubt on the wisdom of that theory. We have done some experiments, a couple with live but uninjured test subjects and more with only a weighted litter. We use either a basket litter or a SKED and backboard. It works extremely well as far as a quick raising or lowering. The litter is not likely to hang up on anything and if rigged correctly you almost never even need an edge person. However that is no help if the patient seizes and dies as soon as we get him moving. Of course, if the subject is uninjured he isn't going to be in a litter anyway so anybody we put in a litter (except for practice) will be injured. So my question: Are there circumstances in which it might be advisable to save time and have the patient vertical? Maybe something like a leg or arm injury without shock? I suspect we will have to abandon the idea of a vertical litter entirely but would like to know if there is any hope.