Source
r/AskReddit•
AND_

I'm an amputee. How the heck does circulation in my remaining limb work?

Had an emergency amputation in Egypt (upper end of the developing world, I guess). So basically, did the surgeon tie my severed veins together, or is my blood just pooling in a sac somewhere? Or do I just need an elementary education into the human circulatory system? I googled around a little bit and understood very little, and figured that Reddit was the place to ask around for this kind of specificity.

Posted May 11, 2011, 3:39 AM UTC

2027
EdgeOfDreams•

Blood flowing out from your heart goes into many 'outbound' veins. Off of each vein, many smaller branches split off. These split even further and further until we're down to capillaries. This is the level at which oxygen can easily leave the blood to enter your tissues as the blood flows past. Now, those capillaries continue on and start merging back together. Eventually, they connect back to one of your 'inbound' veins that heads back to the heart.

So, all along the length of your limb, there's a few major 'inbound' and 'outbound' veins. But not all of the blood goes all the way to the end of the limb and back. Most of it, in fact, gets part way down the limb, goes through some of those thousands of capillaries, and then heads back to the heart.

The fact that the veins have been cut off at a certain point is just not an issue.

14
piotrmarkovicz•

To be more exact with the terminology and physiology:

Red oxygenated blood is pumped from the left side of the heart through muscular arteries (muscular to help maintain the high blood pressure in the system and to absorb the pulsatile pressure of the heart contraction). Those arteries successively narrow and branch off until they end in tiny arterioles and finally capillaries that are only a few blood cells wide. Each branch artery has a capillary bed that it serves, like a trunk supports the branches and leaves of a tree. Most capillary beds overlap to some extent, like the branches of a tree cross over the branches of the neighboring trees. The capillaries are thin-walled blood vessels and at relatively low pressure (due to small cross-sectional area of the vessel and the overall large volume of blood they can hold). It is at the capillaries, in all tissues, that oxygen leaves the blood stream, other nutrients too, and enter the tissues and toxins and metabolic byproducts like carbon dioxide and lactate enter the blood stream to be carried back to the heart. These capillaries continue and start to join back together as thin-walled, low pressure and modestly-muscled (relative to arteries) veins that gradually increase in size and feed back to the right side of the heart. The heart then pumps the de-oxygenated blue blood back to the lungs though arteries that become capillaries and then veins feeding back to the right side of the heart.

If you cut off a limb, you will cut through major veins and arteries as well as smaller veins and arteries and capillaries. To stop the bleeding the big veins and arteries are closed off by suturing (sew) them closed, smaller ones are cauterized (burned) shut and the smallest ones close themselves using our built-in clotting mechanisms. Any tissue that is not being fed sufficiently by the remaining branch arteries will be non-viable and is generally removed as it will die if it is not dead already. The tied off artery will retain its pressure from the effort of the heart and upstream arteries. The tied off vein will collapse unless it is being fed by capillaries as veins have small one-way valves that prevent blood from pooling in veins. Any excess fluid that is forced out of the capillaries into the tissue drains away via a low-pressure, vein-like system called the lymphatic system that eventually drains into the major veins near the heart.

For the arteries, think of an underground sprinkler system. Cap off one of the sprinklers and the other sprinkler heads keep working. The part of the lawn that only got water from that sprinkler head dies but any part of the lawn that got water from one of the other sprinkler heads will do fine.

TLDR; arteries get tied off and maintain their pressure, blood moves through branch arteries through the remaining capillaries before filling veins that return blood to the heart. Any tissue not being fed by an artery and capillary bed is removed as it will not survive. Tied off veins can remain filled at low pressure or collapse as one-way valves prevent backwards flow of blood.

12
xiccit•

well this just makes so much more sense then what i though happened.

2
jhchawk•

In this case, keeping in mind tied off arteries vs. veins, is it worse to have your left leg or right leg cut off? (and right arm vs. left arm)

1
AND_OP•

Huh! I was suspecting it was something like this ("so wait, how does the blood get in and out of my tissue if it's so stuck in the veins?") and I'm really glad you were here to explain it so succinctly. That was really insightful. Thank you so much.

Someone else mentioned that my body maintains the same amount of blood as before my amputation - how could my body handle the extra blood? Like, do my veins stretch out to handle the extra load?

2
EdgeOfDreams•

Actually, it seems unlikely to me that you'd have extra blood. The human body is quite good at self-regulating.

Here's the question: Do tall people have the same amount of blood as short people? Probably not.

I'm fairly certain that the body will adjust it's production of new blood cells relative to what's needed. Most of your blood cells are replaced on a regular basis anyway. On the other hand, most of the actual volume of your blood is plasma, which is 93% water anyway. Your body regulates the amount of water you have in you at any given time by way of sweat, urine, and feeling thirsty.

6
KoNP•

You'd have the same amount of blood PROPORTIONATELY, but the total volume your body has was reduced a bit when you lost whatever limb it was. Not much, mind you. But a noticeable amount nonetheless.

1
[deleted]•

An outbound vein is an artery btw. Veins and arteries actually have very different structures, it's not all just pipes defined by which way the blood is flowing. Blood vessels would be the more appropriate neutral term.

2
[deleted]•

TIL

0
[deleted]•

[deleted]

3
AND_OP•

Haha, well, either I'm a super-human vampire amputee, or it's definitely not that.

1
[deleted]•

I've wondered this as well. My grandmother lost both legs above the knee before she died. And my aunt lost one leg the same way. Both were caused by complications due to diabetes.

2
philosarapter•

life, uh, finds a way.

2
always_lurking•

The first step in an amputation is to litigate (tie off) the veins and arteries and it basically becomes a dead end.

1
Eszed•

Litigate? I thought the word was ligate. I like the image of a swarm of tiny lawyers holding shut your vein, though....

12
[deleted]•

They tie off the (ie, ligate) larger vessels real good, and I suppose they use cautery-type techniques to take care of the smaller ones.

You don't want large vessels just hanging out bleeding into empty space at the end of your limb: it'll put a lot of pressure on the wound and stop you from healing.

They can't really tie the larger vessels together, ie the artery (blood from the heart) directly to the vein (blood going back to the heart), as there is a huge difference in the blood pressures between arteries and veins. This is what happens when they hook up an artery to a vein (done surgically for dialysis access). Your arterial and venous circulations actually connect at the level of the tiny vessels in the target organs/muscles/bone/skin. Often there are multiple vessels connecting in various places (aka collateral circulation) so there can still be blood supply even if some of the big vessels have been cut off.

I hope this is somewhat clarificatory. Operative surgical techniques are for some reason really hard to find written down in places.

Disclaimer: med student, have only seen one amputation and I spent most of the time mentally swearing.

That's a shitty situation you've been handed there, I wish you all the best with rehab and recovery.

1
AND_OP•

Thanks for the well wishes! Things are going well enough, 1.5 years later. It's crazy how disconnected I've become with my (American) doctor over time, though. Basically, once I stopped bleeding all over the place, we ran out of things to talk about.

And also thanks for the awesome overview. It was very clear - clear enough for a liberal arts student like me to get down. So veins and arteries don't directly connect like a one-lane highway for blood cells (which I, for some reason, assumed existed)? They connect through the capillaries which go through the target tissue? That makes the human body way better designed than I was giving it credit.

Also-also, I guess simple question, but when they tie off vessels, do they literally just put a knot in it? Or do they use some kind of wire? In any case, are these stoppers ever going to come undone?

1
BoJyea•

glad to hear you're doing well. as far as "how" its done. its usually with electric cautery. IE: burn the end of the vessels closed. this is usually done aside from the main larger arteries and veins also being tied off with surgical suture(which does not disintegrate over time). The only way these "stoppers" of yours are coming undone is from another traumatic injury to the area.

1
[deleted]•

[deleted]

1
[deleted]•

Heh, I was once like you! Arts ftw.

So veins and arteries don't directly connect like a one-lane highway for blood cells (which I, for some reason, assumed existed)? They connect through the capillaries which go through the target tissue? That makes the human body way better designed than I was giving it credit.

Yes. It's in the tiny vessels that the blood actually reaches the target organs it's trying to oxygenate/deliver nutrients too. Where that happens, it also needs to take away the waste products/de-oxygenated blood. They are low-pressure systems as well.

They tie around the vessels with nylon string, and do that at least twice - surgeons don't want to be called back in the middle of the night because one of the knots slipped. You don't use wire on vessels since it would be quite traumatic. Wires and metal fixtures get used to put bones together, like after they crack open a chest for open-heart surgery. After a few months, the ends of the cut vessels would probably start to fibrose and scar around the suture material. This would make the ligation even more secure. You're probably more likely to spring a leak in other vessels at this stage.

1
fearandloath8•

Hey dude, I'm a 1.5 year AK amputee myself. 23 years old and still getting back into the swing of things. I got a C-Leg and whatnot, but from one to another I hope you continue to rehab well.

1
jecowa•

New blood tubes are able to form to help with circulation. The surgeon definitely did something with your arteries so they wouldn't leak out all your blood into a sac somewhere. I think they heat sear the ends of the arteries.

0
Adrexani•

with no expert opinion from me...

more than likely he cut off the viens that would have led to that amputated limb, so instead of it branching off it just keeps going like it would have, you will also have the same amount of blood as before, but less body space for it, so you will probably end up feeling warmer than usual

grammar nazi's have fun

-1
AND_OP•

My posted question actually branched off (pun) from a conversation on the amount of blood I have now, ha. Which is also something I've wondered a lot about. I do actually always, always feel warm! I thought it was just the insulation by the prostheses, but extra blood would make more sense.

1
BoJyea•

this is completely false. you do not have extra blood. the body regulates your blood volume accordingly with the volume of your total circulatory system(arteries,veins, capilaries, heart, lungs) The body is able to re-route what it doesn't need. For example, if someone is really obese(since they are obese they have many many more capillaries to feed the fatty tissues in their body) when that person loses the weight/burns off the fat the adipose cells are no longer in need of that blood which the body had routed there. therefore, these are no longer used to transport blood through due to the smaller body size of the person. hope this was helpful!!

2
Adrexani•

one of my former teachers had lost a leg when he was about 16 in an accident, and he always liked the temperature in the class to be really cool because he still had all the blood but not as much space to occupy

1
[deleted]•

You wouldn't have the same amount of blood as before. You will have the same proportion of blood to body, but less body -> less blood.

0
[deleted]•

[deleted]

-1
AND_OP•

Ha, real fun, believe me. Thanks for the explanation.

1
[deleted]•

When you lose a limb, they need to take the main vessels and connect them so your circulation is in fact short circuited.

they do not do this. It would be disastrous if they connected the main arteries in the leg directly into the vein. As I said elsewhere:

They can't really tie the larger vessels together, ie the artery (blood from the heart) directly to the vein (blood going back to the heart), as there is a huge difference in the blood pressures between arteries and veins. This is what happens when they hook up an artery to a vein (done surgically for dialysis access). Your arterial and venous circulations actually connect at the level of the tiny vessels in the target organs/muscles/bone/skin. Often there are multiple vessels connecting in various places (aka collateral circulation) so there can still be blood supply even if some of the big vessels have been cut off.

1