Ah yes, the old raisin bagel (vasovagal) response. My first experience with someone who had passed out from a vasovagal reaction was while I was precepting with a medic and that was what they called it in a joking manner. A raisin bagel, play on words and just as common. They occur pretty frequently often in older people especially when straining on the toilet. Yep, that’s right. Lots of elderly passed out near the toilet. Might sound funny but considering how many of them get themselves wedged into position between the toilet and wall that they can’t extract themselves it is far more dangerous to life and in particular limb than you might believe. Especially when they aren’t found for hours or days. Anyways, I digress. This is to just point out that there are lots of ways a vasovagal reaction can actually happen which in this case is actually a Valsalva maneuver causing a vasovagal reaction. Now the rushing of blood into your legs can be a more serious matter then the activation of the vagus nerve by straining causing changes in heart rate and blood pressure. Most people like you just standing around taking pictures of the moose and gets excited because of a perceived threat. The blood rushes to your legs preparing to get you running leaving your brain wanting a little. It feels left out. Things start to go grey then black and fortunately, (you will see why I say fortunately in a minute) you find yourself on the ground maybe wondering how this happened. But this fainting thing is actually a good thing. Why? Well the system is actually working the way it was designed. And by that I mean – Brain gets no oxygen, Brain says not good and turns out the lights. Body now goes level at ground height and brain gets its blood supply back. Greedy brain. Most of us walking around like standard bi-pedals this system works really good. It is self regulating. Like I said, brain has no oxygen, make body fall down, brain gets oxygen back, no harm, no foul.
What happens if you are not operating as a standard bi-pedal human walking around enjoying the sunshine? Well, who is that you might say? Anyone hanging from a harness and not using their legs. People who climb and have fallen and not pushing on the cliff face with their legs, people being rescued in a stokes basket being lowered vertically, people who work in trees hanging from a harness, theatrical people hanging from wires, etc. Adult humans actually have the ability to store their entire blood supply below their waist. Have you ever wondered how your blood gets from your feet back to your heart? Be honest, of course you haven’t. Well the heart doesn’t suck it up. It can’t. So nature has come up with a series of one way valves in the veins of your legs. Every time you move your legs the muscles squeeze your veins pushing blood up towards your heart and the one way valves prevents it from rushing back down. This system works great when you are walking. As a matter of fact when you are running there is actually very little blood in your feet. The command in the army called “parade rest” is in the command set specifically so the legs are not locked at the knees and the muscles can twitch. Unlike the way they are in the position of “attention” which allows the blood to pool in the legs and has caused innumerable embarrassments to privates through history on the parade field. What happens if you aren’t using your legs standing or walking by hanging in a harness? Well this can be problematic. It can actually kill you and it can do it pretty quickly. Anyone hanging from a harness is susceptible to Hanging Harness syndrome also known as Suspension Trauma. We use the same scenario. Hanging from a harness and blood is pooling in your legs. You are not using them so you pass out from lack of oxygen to the brain. You should fall over but can’t because the harness you are wearing doesn’t allow that to happen. What happens when your brain goes without oxygen for more than a short period of time? Correct, you die. You should have several minutes but you actually may have less because your airway may close due to unconsciousness causing respiratory arrest. How strong you are, your age, etc, all have nothing to do whether you will be affected by this.
The ways to avoid it are whenever you are in a harness try to sling another harness under your knees to hold your thighs in a horizontal position. Do not ride an imaginary bicycle. That just causes more blood to rush to the legs “to help” the muscles doing the exercising you are doing so it is counter productive.
Things to watch for. Anyone in a harness, hanging, and complaining of leg pain. That is the first indicator and it is a very bad indicator. It means you need to get his person down fast. Immediately! They may eventually pass out and I just explained what is happening with that.
The leg pain comes from the pooling blood causing an increase in the pressure in the legs. This is causing compartment syndrome. There are lots of causes of CS. You can look this up but the short answer on this is that because they have gone into CS their leg muscles have gone into anaerobic operation and are now producing lots of nasty byproducts and changing the blood chemistry. They have done this because of the buildup of blood in the legs. The items in the blood that have been created cannot be let back to the heart rapidly.
Now what? Well first thing after getting that person to the ground. DO NOT LET THEM LAY DOWN. They must be kept in a sitting position. This is contrary to just about what every emergency worker and most people are going to want to do. Laying these people down can kill them. You must protect their airway if they are unconscious but they must stay seated. The only exception to this is if they need CPR because they are in cardiac arrest. Any indication of Suspension trauma even just leg pain is a required hospital trip.
As a side note the Valsalva maneuver is sometimes used to help a patient with supraventricular tachycardia. It is also diagnostic.
And as always I make no warranties about this information and it not intended to diagnose, treat or do anything medical other than to inform. Always check with your doctor for more or corrected information.
Glad you made it through OK Forestgnome. As always love the pictures.
Regards,
Keith
