Author’s note: This is the fifth diary in a series that I will post monthly, on medical topics related to emergency care. If you want to check out the first diary in the series, you can find it here, on the topic of insider tips to improve your ER visit, and the second one here, on the topic of heart attacks. Some of these diaries will focus on the medical system or process, and some will be disease-specific. My goal, as your friendly neighborhood ER doc to the Daily Kos community, is to provide useful information for this community to stay healthy and get the best results from our medical system. I hope you find it helpful!
You may have been given the advice to get up and walk around on a long flight — or to get out of the car and stretch during a cross-country road trip. Sound advice — and it has to do with preventing a very serious, and common, medical condition known as a Deep Venous Thrombosis (DVT). This condition also has close relative known as a Pulmonary Embolism (PE), a life-threatening emergency. In today’s blog, we will learn about these medical problems, who is at risk, and when to worry about them.
Background: blood clotting, the good and the bad
Anyone who has experienced a cut to the skin or a bad scrape to the knee (which pretty much means everyone) knows that the initial oozing of blood from the wound slows and then stops. This action of blood clotting is a fundamentally important mechanism to keep us alive — and indeed, people who can’t clot well (for example, those with hemophilia) can have serious life-threatening bleeding from minor injuries. All of us bleed at some point; clotting forms a gelatinous patch that stops the bleeding and allows for slower healing processes to take over and repair the wound.
But it turns out that clotting doesn’t just occur on the skin; it can occur with internal injuries as well. In fact, your blood is in a constant dynamic tension between liquid flow and clotting, ever ready to clot over an injury at the first sign of trouble. While this is generally a useful protective mechanism, sometimes it can lead to trouble. If blood flow is too sluggish, or pools due to blood vessel blockages (think highway traffic piling up before a lane closure), erroneous clotting can be triggered. This can lead to a potentially dangerous situation, where a clotted clump of blood cells can form within a blood vessel and travel like a raft, buoyed in a river of liquid, towards downstream destinations in the body.
At this juncture, it is important to review the two basic forms of blood vessels — veins and arteries. Arteries carry blood from the heart to the body, conveying oxygen and nutrients to your organs and muscles. Veins carry depleted blood from the body tissues back to the heart, when this spent blood is then replenished with oxygen in the lungs before it makes another cycle through the arteries. So now, perhaps, the danger is more clear — if you have a blood clot in a large vein (say, a vein in your leg), it could travel up the vein, through the heart, and into the lungs, where it could get wedged and block the normal ability to pick up oxygen and feed your tissues. That sounds bad, right?
Deep venous thrombosis and pulmonary embolism
When a blood clot forms in the leg, it is known as a deep venous thrombosis (or DVT). In most cases, a DVT gets stuck in the vein and creates a traffic jam of blood trying to leave the leg, much like a clogged kitchen drain can lead to a full sink. This back-up in the veins presents itself as leg pain, swelling and sometimes red discoloration to the leg, usually in just one leg — after all, the chances of simultaneous blood clots in both legs are unlikely (medical practitioners speak of “unilateral” leg swelling, one leg, or “bilateral” leg swelling, both legs; bilateral swelling is much less likely from blood clots).
So — if you ever find yourself with one swollen and tender leg, seek medical attention promptly. A DVT is a strong possibility, and it always requires treatment to help dissolve the clot. We’ll get to treatment a bit later on. One of the key reasons to treat a DVT is to relieve the symptoms of swelling and pain by opening up the veins for blood flow once more, but the more important reason to treat the DVT is to prevent the more dreaded complication: a pulmonary embolism (PE). A PE is when a piece of the blood clot in the leg breaks away, and travels up the vein, through the heart, and wedges into the blood vessels of the lung. Most DVTs do not turn into PEs, but they could — and the consequences can be serious, even life-threatening.
When a clot flicks off and travels into the lung, it usually causes symptoms of sudden onset chest pain, difficulty breathing, and a fast heart rate. Sometimes people can develop a cough, and sometimes the PE can cause fainting. For this reason, when ER docs like myself see patients who have unexplained fainting, we sometimes are compelled to evaluate for PE as the cause. Usually, a PE results from a recent DVT, but not always. So if you experience sudden chest pain and difficulty breathing, but don’t have a swollen leg, it does not mean that PE is off the list. Tricky stuff, which is why sudden onset breathlessness and/or chest pain is not to be taken lightly. It almost always needs medical attention promptly, since the list of possible causes includes a number of life-threatening conditions that includes PE.
Why is PE such a big deal? Well, there are two big reasons: in bad cases, it can lead to cardiac arrest soon after it occurs, because it throws off the hemodynamics of blood flow in significant ways. That is, PE can kill. While most PEs don’t lead to death, a second major problem exists: PE can lead to chronic difficulty breathing and secondary lung complications that are sometimes debilitating. Said another way, PE really must be treated in most cases, it cannot be ignored.
So . . . how do I know if I’m at risk of a DVT or PE?
There are a number of risk factors that make DVT more likely:
1. Genetic predisposition (if DVT runs in your family, make sure to tell medical providers about it)
2. Recent immobilization (e.g. a week in bed due to a serious illness, a leg fracture with a cast, etc)
3. Long travel (e.g. flights or long car trips over 3-4 hours in duration)
4. Oral contraceptive use (only the kinds with estrogen, not the progesterone-only ones)
5. Active cancer (almost any cancer can decrease the threshold for abnormal blood clotting)
6. Significant leg injury (such as a leg bone fracture)
This is why it is important to get up and walk around a few times on long flights, and take a stretch break on long car trips — you need to get the leg muscles working so keep the blood from getting sluggish in the veins. If anyone arrives in my ER after just getting off a flight from Europe or Asia, and has chest pain — DVT and PE are high on my worry list. Some people take an aspirin before a long flight, since aspirin tips the scales a bit towards bleeding and away from clotting — I wouldn’t recommend this without consulting your health care provider first. Aspirin isn’t right for everyone.
While genetic predisposition, use of birth control pills, and active cancer represent risk factors that are harder to modify — it’s still important to realize they put you at slightly higher risk of clots. If you are getting chemotherapy for breast cancer, for example, and you suddenly develop chest pain — PE is the concern. If you are taking estrogen-containing oral contraceptives, ditto — chest pain and difficulty breathing needs evaluation.
I’m in the ER: how will the medical team check me for DVT or PE?
If someone arrives in the ER with unilateral leg pain and swelling, the key test they will likely perform to evaluate for DVT is an ultrasound evaluation. It is relatively easy to do, doesn’t hurt, and is safe to perform. Using ultrasound, we can see the veins, and visualize any clots that have formed. A negative ultrasound evaluation rules out a DVT as the cause of swelling and pain in the vast majority of cases. The other test, useful for both DVT and PE, is a blood test known as a d-dimer test. This blood test looks for breakdown products of blood clots — if elevated, it suggests DVT and PE are more likely.
If someone arrives in the ER with chest pain and breathlessness, we may perform a d-dimer test, but often we also perform a CT scan of the chest (computed tomography test, sometimes known as a “CAT scan”) — a form of x-ray where we can look at the blood vessels in the lungs and find clots. This test isn’t without some risks. If you undergo a CT scan, you receive radiation exposure. A chest CT looking for PE also requires intravenous injection of what is called “contrast material” to “light up” the blood on the images, and contrast material occasionally provokes an allergic reaction; contrast material also has a small risk of injuring the kidneys. These risks are small, but real, so sometimes an ER team might not recommend a CT if they think the risk of a PE is low enough.
Unfortunately, there are no physical exam findings, nor any symptoms, that are unique enough in patients with DVT or PE to allow for diagnosis without blood testing or radiographic testing. What this means is: you really do need to seek medical attention at an ER if you have symptoms that might be a DVT or PE. Furthermore, you really shouldn’t go to an urgent care clinic for DVT or PE concerns — it’s above the technical abilities of most urgent care sites to manage this evaluation and treatment.
What is the treatment for a DVT or PE?
The main treatment for DVT/PE is medication to tip the dynamic balance of clot formation vs. clot dissolution away from clotting. Said another way, “blood thinning” medication is required. The term “blood thinning” confuses people, and rightly so: there is no “thinning” going on. Medications such as heparin, coumadin, xarelto, and eliquis change the chemical dynamics of the blood to favor clot disruption, they don’t do anything to viscosity. Still, most people have heard of this class of medicines as blood thinners. Heparin is the most commonly administered medication in the ER setting — it is given via IV, or sometimes a form of it can be injected under the skin (a form of heparin known as enoxaparin, or by its brand name lovenox).
Here’s the problem: ER treatment is not sufficient. When diagnosed with either DVT or PE, treatment is required for several months and often longer. The oral medication coumadin used to be the most common treatment, but now easier to manage options exist, known by their brand names as xarelto and eliquis. A problem with all of these medications is that they inhibit blood clotting (that is their purpose, after all) — which means people on these medicines bleed much more than usual. A slip in the kitchen resulting in a cut finger can result in quite a bit of bleeding, as can flossing the teeth. Bruising is more common as well. More significantly, the risk of life-threatening bleeding is higher as well, such as brain bleeding if someone falls and hits their head. For this reason, some people with DVT or PE are not put on blood thinners if the risk is felt to be too high. A classic dilemma is the elderly patient with newly diagnosed PE, who has frequent falls at home and at one point broke her nose falling in the bathroom. A physician would be very hesitant to place her on coumadin, and would have to weigh the risks of complications from PE versus the risks of brain bleeding from a fall. Very challenging, and unfortunately this dilemma happens all the time.
Where can I learn more?
Here are some free resources that I recommend for additional reading on DVT and PE:
National Institutes of Health website on DVT and PE
Stop the Clot nonprofit organization page
UK webpage resource on DVT and PE with good videos
I hope you found this diary helpful, and as per my usual habit, I will stick around today to answer questions. The doctor is “in”!