eli5: How do amputees survive but people can die from a slit on the wrist or cut on the femoral artery?
In: Biology
People who lost a limb do not always have it completely severed. Usually the effected limb is damaged enough that it won’t heal and isn’t repairable but still attached. If the major arteries aren’t damaged then the person is likely to survive long enough to get medical care. The part of the limb that is too damaged to save is removed at the hospital.
Amputees do not survive without urgent medical treatment or a very tight tourniquet.
Chances of surviving a slice of a major artery will generally be better than the amputation, which is to say you might have a few extra seconds to get to those treatment options.
I am pretty sure you will likely bleed death from an uncontrolled amputation.
Also, a slit on the wrist will only kill you if you let it, if you treat it you will probably not bleed to death, but both the wrist and some specific arteries are places that just bleed a lot without being easily stopped by your body.
Im not a good source though, there is probably more to it, but yeah if you cut off your leg clean you will likely bleed to death, people that survive losing limbs often had it crushed and trapped or not completely severed before having their limb amputated in a controlled environment, having your hand cut off with a blade will probably kill you if you cant stop the bleeding though.
what you are seeing is survivorship bias. you only see the amputees that survive thus you consider that they all survive….
a medical amputation is well planned and managed surgery with multiple measures in place to limit bloodloss and seal arteries/veins. an accidental or traumatic amputation is a very different, VERY dangerous situation where despite natural instincts such as shock acting to limit blood flow, death is not that uncommon.
a lower arm/hand amputee will have a much higher likelihood of survival by comparison to an upper arm, and an upper leg traumatic amputation would be nearly un-survivable without immediate assistance and great luck.
Alright, people are giving some pretty good answers here but none of them are really correct. I am not going to talk about surgical amputations because I don’t think that’s really what you’re asking about.
Long story short, all traumatic injuries have the potential to be fatal and need to be treated in a hospital. You can buy somebody time in the field but they will still die without access to definitive care (I.E. trauma center). It’s important to note that any injury that isn’t immediately fatal can typically be treated with direct pressure and/or a tourniquet to greatly increase the chance of someone surviving.
The reason why people have a greater tendency to survive after an amputation is because the blood vessels are completely severed and can spasm, pull back into the body, and shrink. This can lead to less bleeding from the wound itself. EVENTUALLY, the patient will lose enough blood that they will become unconscious and the blood vessels will relax and start bleeding again. This is why a tourniquet should always be applied to an amputation.
Depending on how a wrist is slit (horizontally vs vertically) the same thing can happen to the vessels in the wrist. The problem is that this doesn’t always happen and even when it doesn’t, it doesn’t always lead to complete stoppage of bleeding. Alternatively, if cut in a certain way the mechanism that causes the vessel to shrink and spasm will rip it apart, leading to more bleeding. Again, a tourniquet should still be applied if available and at the very least, direct pressure should be held.
The common femoral artery is a very large vessel and you can bleed out from it very very quickly (I believe the only vessel larger than it in the body is the aorta). There is still the possibility of it closing off if completely severed (as in an amputation) but it is less likely and even if it does this it will still eventually stop being constricted and continue bleeding profusely. When it comes to an arterial bleed in your leg there is a strong possibility that you will end up needing 2 tourniquets placed in sequence to completely stop bleeding. If you do not have a tourniquet you should still attempt applying direct pressure.
Finally, I’m not a doctor. Everything I said could be entirely wrong. I also may have made a bunch of grammatical mistakes, it’s pretty late right now.
[This is a video on everything you need to know about bleeding control](https://www.youtube.com/watch?v=WGLLXy3AsBQ&t=82s&ab_channel=PrepMedic)
I believe the mark has been missed on the answers so far.
When a vein or artery is severed there are a few protective measures inside of the body to stop bleeding. One that most people are familiar with is platelets and clotting. But there are also muscles that surround the vessel which control dilation. When the vessel is severed these muscles contract to slow the flow of blood through them. There are also sphincters which control blood flow in and out of the capillary beds. Lastly vessels are “stretched “ (under tension) to their attachment points.
When a vessel is dissected (long transverse cut) these protection measures cannot kick in. The muscles are circular so they cannot contract to close the wound. The vessel remains stretched so it cannot collapse on itself.
With an amputation these measures tend to kick in and limit the amount of blood loss. The vessel contracts back toward the body making it narrower, the muscles contract making it yet smaller. Hopefully with this the pressure at the end of the vessel is low enough that the clotting factors can kick in a stop the blood flow completely.
Generally? Time until treatment. Modern amputations are generally done in a medical setting where the tools to stop the bleeding immediately are ready and waiting before the surgeons start the operation.
In an accident where a major artery is severed, you have maybe a minute to get medical care before you lose too much blood and die. You can extend this with emergency medical care, like putting pressure on the wound or a tourniquet if it’s in a good spot for it, but at most you’ll extend your time to a few minutes.
In an attempted suicide, the person usually makes sure they’re alone where no one will find them and call for help, sometimes even cutting off their own lines of help in case they get cold feet after the deed is done. They don’t have to cut quite as deeply, because they can have hours to bleed out alone before anyone finds them. As long as the wound keeps bleeding, they’ll likely fall unconscious long before they’re dead, or even past the point where it would be difficult to save them.
During a Surgery.there are methods to control the bleeding that are already in place ready to be used before any cuts are made. You can burn the stump, use a clotting agent and many other things to stop bleeding in a controlled environment. These don’t exist if you get into a knife fight for example and the bleeding is much harder to stop is all you can do is apply pressure with a t shirt. You can also give a person blood in a situation it is needed when amputating.
In cases of amputation, hemostasis or stoppage of bleading is done. In case of femoral or any large artery injury, bleeding is uncontrolled and rapid. This leads to low blood volume leading to shock. Thus there is less blood in system to brain, heart, lungs, kidneys, etc. This causes the organs to reduce function due to reduced oxygen supply and accumulation of metabolites.
The human body depends on the pressure generated by contraction of heart to get blood flowing from larger to smaller vessels. The reverse happens in case of veins. The atria create negative pressure gradient, pullling blood from capillaries towards the heart. Loss of pressure in any part of the system, reduces the flow. Imagine the femoral artery is a water hose. When its cut at one point, water rushes out and the system looses pressure. But if you clamp the hose, a bit before where you intend to cut it, the pressure inside is not affected.
So its a combination of loss in pressure and reduced blood volume that leads to death in case of large artery injury.
I’m not a doctor but from what I understand, sudden amputations result in the body going into shock which changes a number of systems in the body, especially the central nervous and circulatory systems.
Controlled amputations are cauterized to stem the bleeding.
A cut does not send the body into shock, so in the right spot and the right depth could be deadly.
Again, not a doctor so I could be very wrong. Someone correct me if so.
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