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Advanced Wilderness Life Support (AWLS)
Hanging in the Balance: Understanding Suspension Trauma
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Foreign. This is awls podcasts on wilderness medicine from the university of utah school of medicine. Welcome everyone to the Advanced Wilderness Life Support Podcast. My name is Matthew McKinnon. I'm speaking to you from the University of Utah at the Spencer Fox Echols School of Medicine in Salt Lake City. Today we're going to be diving into a critical yet often overlooked topic which is suspension trauma. Whether you are an outdoor enthusiast, a first responder, wilderness medicine professional, understanding this condition could save lives. A little bit of my background so I am a longtime canyoneer and this is something that I have thought about on many canyoneering expeditions. Oftentimes I've seen this topic discussed in online forums anytime there is an unexplained mortality in a canyon or a canyoneering accident. Oftentimes we've never we don't get the full pathology autopsy report and so we don't know exactly what the cause of death was, but this is an often discussed topic in that setting. Despite how often I see this discussed and in online settings surrounding trip reports and accident reports, I have very rarely seen this discussed on trips. Oftentimes when I am on trips with my companions, I have brought up this topic and received blank stares in response. I believe that this is an important topic to know about so that you can be prepared to protect yourself and protect others who you go outside with. I believe that anytime somebody is playing on ropes, involved on ropes, working, if you are going to be suspended in the air from a rope, then it is important to know about this syndrome. So what is suspension trauma? Suspension Syndrome this has many different names. It's sometimes called harness syndrome, harness Hang syndrome, harness induced pathology, orthostatic shock while suspended. These are all describing the same phenomenon. This is a life threatening condition that occurs when a person is suspended motionless in the air for an expense for an extended period of time. It can happen in a variety of settings such as rock climbing, caving, canyoneering, tree climbing, technical rescue, helicopter rescue. It is also an occupational hazard for many many workers and this can occur in industrial settings. Construction workers can be at risk, linemen, painters, window washers, any professional who relies ropes and harnesses to provide safety and access in their work. This makes this topic relevant to both wilderness settings and urban settings. Anytime a rope and harness is involved in your activity, you should be aware of suspension trauma and be prepared to mitigate risk. It's crucial to note that this risk isn't theoretical. It can occur in anyone who is left hanging for too long and a significant portion of the population has been shown to be at increased risk. So what are the signs of suspension trauma? Suspension trauma can develop very rapidly, often within minutes. Initial symptoms may include lightheadedness or dizziness, Followed by a loss of consciousness. In experimental settings, passive hanging has led to unconsciousness in as little as three minutes. Another study found that 30% of their sample of 40 experienced pre syncopal symptoms before an hour of hanging, with the mean being at 44 minutes of suspension. But the minimum time to onset was 13 minutes suspended. In that particular study, early signs to watch for include nausea, vertigo, sweating, changes in vision, and ringing in the ears. These symptoms signal that blood circulation is being compromised, and immediate action is necessary to prevent more severe outcomes. Talking Physiology what happens inside the body when a patient has suspension trauma? The pathophysiology of suspension trauma is still evolving, and this is where some of the more important insights have been emerging for a long time. The dominant theory was straightforward. Someone hangs vertically, blood pools in the legs, venous return drops, and the patient develops hypovolemic shock. That explanation makes intuitive sense, but it turns out it's probably incomplete and in some cases, incorrect. Let's start with what we know. When someone is suspended motionless, gravity absolutely does shift blood into the lower extremities. In controlled studies, research researchers observed about a 50% increase in the diameter of the superficial femoral vein when participants moved from lying down to standing. That tells us the veins are filling and distending quickly. That's lying down to standing after suspension. Here's the key update that pooling alone does not seem to explain why people pass out. Why? Because even though all participants in these studies had venous pooling, only about 30% developed pre syncopal symptoms. If pooling were the primary cause, we'd expect everyone to become symptomatic. And that's simply not what's happening in these situations. Even more importantly, the expected physiologic response to reduced preload isn't occurring what we typically see in hypovolemic shock. If blood pooling were significantly decreasing cardiac output, we should see a drop in stroke volume and an increase in heart rate. Instead, what researchers have found is that there is no meaningful drop in stroke volume in these cases and no compensatory tachycardia. And then right before the pre syncope, there is a sudden drop in both heart rate and blood pressure. That pattern doesn't really look like hypovolemic shock. It looks like a neurocardiogenic event. So our newer thinking on this issue of suspension syndrome is that this is not necessarily just a hypovolemic issue from blood pooling in the legs, but but it's more a reflex mediated circulatory collapse. This is the current leading explanation is that a prolonged motionless suspension is creating orthostatic stress, triggering a neurocardiogenic reflex which decreases vagal tone and decreases sympathetic output. This results in bradycardia, vasodilation, sudden hypotension, and ultimately loss of consciousness. We used to think that this was attributed to decreased ventricular filling and that the decreased ventricular filling was triggering a response. But even that is being called into question with more recent studies. Echocardiography has shown that cardiac preload often remains adequate even in symptomatic individuals. So this really may not be due to low volume at all. Instead, it seems like the body is reflexively shutting down circulation despite adequate preload. Now, to be clear, this is still debated. There's likely no single mechanism and multiple processes may be happening at once. Suspension syndrome is not just one problem, it's potentially several, happening simultaneously. For example, we also know that rhabdomyolysis can occur in these cases, leading to releasing myoglobin into the bloodstream and potentially contributing to kidney failure. Pain, trauma or hypothermia may amplify the physiologic stress and increase susceptibility to collapse. Then immobility itself reduces the effectiveness of the lung muscle pump, which worsens that venous stasis over time. Now, I want to take a moment to talk about a myth that that was occurring in the treatment of suspension syndrome, which was the idea that harness straps would compress the femoral veins and cause this problem anatomically. That doesn't hold up. The superficial femoral vein runs along the anteromedial thigh and the harness load bearing straps are more posteriorly, they're putting their pressure more on the back of the legs. Ultrasound studies have confirmed that, that when somebody is suspended in a harness that these vessels remain patent and that there is no significant compression from the harness straps. Previously, people would say that when you were treating somebody for suspension syndrome that it would be. It would be important to remove the harness as quickly as possible. It seems like that is not a significant contributing factor. The main issue is that passive motionless suspension. That being said, the type of harness that you use still matters. Very rarely being employed these days, but still on occasion, particularly in industrial settings, we see chest only harnesses. These are harnesses that don't have a body component, that don't have hip or leg loops. These Harnesses, when used alone, can significantly worsen the physiology of suspension syndrome. And they restrict the chest wall expansion, making it so that the patient cannot take a full breath. They reduce that tidal volume and they increase intrathoracic pressure, decreasing venous return to the heart, decreasing preload, reducing cardiac cardiac output output and resulting in a very accelerated decompensation. In the studies that they've done with these chest only harnesses, severe symptoms occurred in as little as just a few minutes. Often these harnesses attach from the back, so the patient is truly just suspended in the air with no ability to self rescue. So with these chest only harnesses, even while the harness doesn't block any blood flow in the legs, there are no straps that are contributing. We still have that venous pooling in the legs and these harnesses can absolutely impair respiratory and cardiovascular mechanics. So how do we prevent suspension trauma? Prevention is always the best strategy. In matters of illness or injury. An ounce of prevention is worth a pound of cure. For sports enthusiasts and workers who rely on body body harness systems, it is key to never operate alone and choose your harness well. A well fitted sit harness which does not cause discomfort when suspended, is preferable. This type of harness has been shown to have a lower risk of cardiopulmonary complications, especially when compared to ch only harnesses which should be avoided. Another aspect of prevention is to have a contingency plan in place. This includes training for self rescue and establishing a quick response plan in case of an emergency. I truly believe that self rescue is the best form of rescue and being ready to take care of yourself and take care of your group is the way to go when it comes to preventing suspension trauma. One of the reasons that I am so passionate about this issue is that when I have spoken with many groups while I am out canyoneering, I have asked about their contingency plans. What would you do if somebody ended up suspended in the air? And unfortunately, the answer that I have received many times is well, I guess we would wait until search and rescue came to save us. It's important to note that suspension trauma occurs much faster than a search and rescue team can get to you. With that in mind, it is important, an important aspect of responsibility to be prepared to take care of yourself and your group and to self rescue quickly and efficiently. In cases where somebody may end up suspended in the air, talking about what to do if you are the one suspended and you are waiting for rescue, one effective method to prevent suspension trauma is to keep moving your legs or to place yourself in A horizontal position movement of the legs helps activate the muscle pump in the legs, which can restore circulation and prevent blood from pooling in your lower extremities. You can also find a spot to stand or brace yourself. This is primarily an issue of free hanging repels of being suspended without anything to stand or grab onto. If you are rock climbing and there is a ledge next to you, at the very least take moments to stand on that ledge to reduce the amount of pressure in the in the in the legs. Take time to move those legs around, get those muscle pumps moving and put yourself in a horizontal position on intermittently and then keep an eye on those early warning signs that we talked about. Things like changes to vision, feeling dizzy, all of those things that can signal the onset of suspension trauma from a treatment perspective. How do we treat suspension trauma? So when it comes to treating suspension trauma, time is one of our main factors. If someone is showing symptoms of pre syncope or has lost consciousness while suspended, they need to be rescued as quickly as possible, ideally within five to 30 minutes. I want to remind you that in some of these cases, onset of symptoms has taken place in as quickly as three to five minutes. While in many cases you have a longer time period, the portion of the population who is who is susceptible to this neurocardiogenic reflex may experience symptoms much quicker than you anticipate. A common myth that was being propagated in treatment to suspension trauma was that a rescued individual should be kept upright or squatting for 30 minutes before being laid down to avoid a sudden death from acute volume overload or exposure to waste products in the returning blood. This recommendation is not supported by modern understanding of physiology and has not stood up to scrutiny. Instead of your priority should be to follow standard resuscitation measures to restore circulation to vital organs immediately. This means that rescuers should not hesitate to place the victim in a horizontal position as soon as possible after extrication. High quality CPR and other resuscitative measures should be initiated if necessary. If the victim remains unconscious or is experiencing severe symptoms, rapid evacuation to a nearby hospital should be initiated. If there's concern about potential kidney failure due to rhabdomyolysis, evacuation to a hospital with dialysis capabilities may be necessary. So let's do a quick review. What are the things that I think everyone should take away from this podcast episode? First, I want everyone to know that suspension trauma is a serious condition that can develop quickly and with potentially fatal consequences. Awareness, prevention and rapid response are the cornerstones of managing this syndrome. Let's Talk about awareness it's important to recognize the signs of suspension trauma such as pre syncope, nausea and loss of consciousness. If somebody in your group is suspended in the air and begins experiencing any of these symptoms, be aware that this could be suspension trauma prevention. Make sure that you use a that you use a harness properly. If you are suspended in the air, keep moving, move those legs, put yourself horizontal at times, and never work alone in situations where suspension trauma is a risk. And then let's talk about response. If someone shows signs of suspension trauma, rescue them quickly, lay them flat and initiate standard resuscitative measures. Avoid outdated practices like keeping the victim upright post rescue and be prepared for rapid rescue. You should have a plan in place to rescue somebody quickly in the case that they become suspended. It is paramount that when you go into these situations you have the ability to self rescue. Self rescue is the best form of rescue. Be prepared to take care of members of your group in the sport of canyoneering, a sport that I spend a lot of time practicing, there are many different ways that you could approach this. You could have a second line that you could rappel down to try to rescue and your the member of your group. You could block the other half of your rope, your retrieval line, and you could rappel on that to go rescue the member of your group. Be prepared to climb a rope to ascend. If you get stuck and are unable to continue descending, be prepared to convert your system into a raise or lower system so that you can rescue somebody. These are important tools in the toolkit of canyoneering and other rope access sports, Rope access occupations. Knowledge on how to do these things is widely available in courses and online. Educate yourself, be prepared and be ready to take care of yourself and the people in your group. My hope is that this podcast can increase awareness on this issue and that by understanding and preparing for the risks associated with suspension trauma, you can make a difference in the personal safety and safety of those around you and prevent negative outcomes. I've mentioned canyoneering quite a bit on this podcast. If any of you want to learn more about canyoneering and the medical component of being prepared for canyoneering accidents in the backcountry, we do have a previous podcast episode called into the Slot that is absolutely worth your time to go check out. I want to say thank you to all of us for joining us on this episode of the Advanced Wilderness Life Support Podcast. I hope that you all stay safe out there and that you remember that knowledge is your best tool in the wilderness. If you found this episode helpful, please share it with your friends, colleagues and fellow outdoor enthusiasts. Thank you for your time and thank you for joining us here on the Advanced Wilderness Life Support Podcast. Sam.