How does a blood clot in the lung kill you?

intermittent compression device

Have you ever visited someone in a hospital after surgery and wondered about those big plastic sleeves around their legs, that were attached by air hoses connected to a bedside machine that made a periodic whoosh sound? Have you had surgery yourself and wondered why the nurses put elastic stockings on your legs? In the last few years, airlines have put ads in their in-flight magazines telling you to stretch and walk around. Are you curious why? This article seeks to explain these things. Its lessons just might save your life or the life of someone you love. After reading it you shoul be able to answer the question” how does a blood clot in the lung kill you?” First, however, in order to understand the concepts of this article, you may need a basic review of the human circulatory system and “blood clots”.

The Human Circulatory System

Blood circulates through your body like this:

Your muscles, organs, and bones need the nutrients that blood carries to thrive. When blood arrives at the various parts of your body, the parts remove the nutrients (including oxygen) and send the depleted blood, with waste products like carbon dioxide, through your veins into the right side of your heart. This oxygen-poor n blood from the right side of your heart is then pumped through your lungs where carbon dioxide is released (by exhaling) and oxygen is taken in (by inhaling). The now oxygen-rich blood then goes through the lungs into the left side of your heart (your central pumping station) and is then pumped through your arteries back to the various oxygen-hungry parts that started this cycle. The parts then once again extract the needed nutrients and return the depleted blood back through the veins (see the difference now between veins and arteries?) Over and over your body does this. Day in day out. Unless something develops to stop it. Something like blood clots.

Blood Clots

When you get a cut, the reason you don’t keep bleeding and bleeding is because your blood has something in it that makes it “clot.” Something that makes it thick enough to stop the blood from flowing out. Clots, then, can be good things – when they just seal off a leak.. But sometimes these clots can form even when there is no cut – on the inside – in one of your veins. When this happens, the clot is called a thrombus If some or all of that clot moves to another area of the body, the clot is then called an embolus. But unless you really want to know the difference between a thrombus (the stay-at-home clot) and embolus (the wandering clot), you can forget these names right now and remember only this: when a clot forms in your vein, it can be very dangerous.

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The Life And Times of A Blood Clot

Most clots form in veins, specifically, the veins in the lower legs. One thing that can happen when a clot forms in a leg vein is that it may completely block the vein. . If enough of the veins in a leg are blocked by clot, the flow of blood back to the heart is reduced. When this occurs the blood behind the block may begin to back up. If the veins are not re-opened, the blood begins to collect, or pool. Picture a faucet running into a clogged sink drain. The water keeps running and the sink keeps filling. But when water keeps running into a clogged sink, the water will rise until it runs out of the sink. In the body, however, the blood has no place to go. It simply keeps collecting and collecting until it is pushing on all the muscles as well as the veins and arteries in the leg. When this happens the leg may begin to swell, and may shut down more veins and more arteries until there is no room for new blood to get in or old blood to get out. If this process is not stopped, the leg will then turn blue and the tissue below the block can begin to die. The end result is gangrene and probably amputation of the leg. When this happens, doctors call it compartment syndrome.

diagram of blood clots in the leg and how they form

While losing a leg is, of course, a bad thing, there is something worse that clots can do. Clots can kill. Here is how.

When a clot forms in a leg vein, it usually attaches to the vein wall. However, a clot can break into pieces or just simply break off from the vein wall. If this happens, it can ride the blood stream through the body through the heart, and into the lungs where it will become lodged in one of the lung arteries. When this happens, it is referred to as a pulmonary embolism.

A very large pulmonary embolism can cause an instantaneous cardiac arrest. A small or moderate-sized pulmonary embolus may cause no symptoms at all or may cause symptoms such as sudden shortness of breath, bluish coloration of the skin, rapid breathing, anxiety, restlessness, chest pain, spitting up blood, or a rapid heartbeat. Most of the time if a person does not die immediately from a pulmonary embolus, he will survive unless he has a second embolus.

If an embolus is large, but is not immediately fatal, the blood pressure in the lung arteries rise. The right side of heart then has to pump harder than usual because it must overcome the higher pressure and may not to be able to pump enough blood through the lungs. . (Remember, blood goes through the lungs to get oxygen and then is returned to the heart. If there is less blood going through the lungs in the first place because of the clot, there is less blood to return). As the heart works harder and harder it will get bigger (enlarged heart) until it can work no more. Then it simply stops.

What makes a blood clot in the leg vein so dangerous is that it often doesn’t reveal itself until it has lodged in a lung artery (becomes a pulmonary embolus). And once that happens, once the symptoms show up, death is not far behind, at least with large clots. In other words, there is very little that a doctor can do to save a patient once a large clot gets to this stage. So, what a doctor must do to prevent death from a pulmonary embolism is to prevent the clot from forming in the first place. This is where those stockings and those sleeves with air hoses come into play.

The Risk Factors for Blood Clots

While the exact mechanism for clot formation is not fully known, doctors do know that certain conditions are commonly associated with the formation of clots. These conditions are called “risk factors” by the medical community. When a patient has a certain number of these risk factors, doctors must take steps to prevent clots from forming. Some of the risks factors for clot formation include:

  • Having a close family member who has had a pulmonary embolism
  • Blood clotting disorder (person does not clot the way a normal person does)
  • Recent surgery (surgery with anesthesia lasting longer than ½ hour)
  • Fractures to the hip or legs
  • Standing or sitting still for long periods of time, such as on a long plane trip or car ride (the reason why airlines like to get you walking)
  • Cancer
  • Obesity
  • Smoking
  • Older than 55 (although this factor has been questioned as of late)
  • History of a heart attack or stroke
  • Pregnancy, taking birth control pills, or taking estrogen replacement therapy

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Preventing Blood Clots – Taking Charge of Your Care

Advice that CHH consistently gives to their clients is that one of the best ways to prevent medical errors is by being actively involved in the care they receive. In the medical arena, the patient is king, so act like one and take charge of your care.

If you have any of the risk factors for blood clot formation (fly a lot, take birth control, not active, etc) ask your doctor if you need to be concerned about blood clots. If you (or loved one) are about to undergo or have undergone a surgery, ask these questions of your doctor: “Are you concerned about blood clots during or after surgery?” “Why not?” “What about the fact that I’m (on estrogen; obese, older than 50 or other risk factors you possess?)” Ask her specifically what she intends to do to prevent blood clots from occurring. Some of the things she may recommend include:

  • getting you quickly walking around (they call it “early ambulation”);
  • using elastic stockings (she will likely call them “TED hose”);
  • using the sleeves or boots with the plastic hoses (she will call them “SCD’s” or “sequential compression devices”)
  • prescribing a medication that reduces clotting risk, such as Coumadin or low dose Heparin
  • using a combination of some or all of the above

Regardless of what method your doctor recommends, keep in mind the following and ask questions or make demands of your doctor accordingly:

  • early ambulation means getting out of bed early in the recuperation period (day of or day after surgery) AND substantial movement, such as repeated laps around the halls. Walking from bed to chair or bathroom and back is NOT enough;
  • elastic stockings have not been shown to be very effective in clot prevention and if misused can actually be dangerous. Stockings should never be used as the only method of clot prevention. Also, to be effective at all, they must be fully applied on the legs. They should never be rolled only part way up, or part way down. If that happens, the part that is “rolled” can act like a rubber band that squeezes the leg at one isolated junction. Instead of helping prevent clots, this rubber band effect can actually cause them.
  • SCD’s (the boots with air hoses) have been shown to be very effective, but only when they are actually used. (They work by squeezing your legs to keep the blood flowing). The sleeves can be inconvenient to put on and off when a patient begins to walk around so sometimes nurses just leave them off. Bad idea. Especially bad in the first few days after surgery when the patient is not moving around much. The rule is that whenever the patient is going to be sitting or lying still for more than a half hour, the boots must be applied (attached with air hoses making whooshing sound).
  • doctors used to think that the use of heparin or other medications which limit clotting could be dangerous (may cause excessive bleeding). Current research has shown such fears to be unfounded with respect to most types of surgery and with respect to most patients. If your doctor gives this reason, question it or ask for a second opinion.

Which prevention method your doctor must use depends upon the risk factors. So, if you have any doubt whether your doctor is doing enough, ask her. Challenge her. Take charge of your care.


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At Cirignani Heller & Harman, LLP, we represent Illinois clients in Chicago and throughout Cook County, including the cities of Cicero, Elgin, Schaumburg, Oak Park, Maywood, Berwyn, Elmhurst, Evanston, Skokie, Des Plaines, Mount Prospect, Arlington Heights, Palatine and Hoffman Estates. We also help clients in DuPage County, Kane County, Lake County, McHenry County, Will County and Winnebago County. If you have been the victim of medical malpractice in Illinois, CHH Law is the law firm with attorneys that can help.

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