One of the most feared complications of surgery is a blood clot that forms in the veins of the legs and travels to the arteries of the lungs. It’s called a “pulmonary embolus,” or PE. Even though hospitals and doctors do many things to prevent PEs, informed patients can play an important role as well.

Here, we’ll talk about what exactly a PE is, and what you can do to minimize your chances of getting one.

So, What is a Pulmonary Embolus?

Let’s start with a definition. “Pulmonary” means lung, and “embolus” means something that started in one place and moved to where it’s causing problems. In the case of a PE, that means a blood clot that formed in a vein somewhere in the body and moved to the lung.

Why Are PEs a Problem?

PEs usually form in the deep veins of the leg, as what are called deep venous thromboses¹ (DVTs). Then they break free, travel through the veins up to the heart, and get pumped out to the lung, where they get stuck in branches of the pulmonary arteries. This causes problems for two reasons:

1. The PE can block an artery, meaning that part of the lung can’t help get oxygen into the blood. Some blood going to the lung leaves without getting oxygen, so your body may not be able to deliver enough oxygen to other organs.
2. Blockage in the lung causes pressure to build up in the heart. If the heart is trying to pump blood against a blocked artery, it has to work harder. Severe cases of PE can cause a heart attack or heart failure.

Obviously, these are not things you want to happen. Although there are good treatments for PE – mostly different kinds of blood thinning medication — the best thing is to keep one from happening in the first place.

What You Can Do before Your Operation to Help Prevent Pulmonary Embolus

Talk to your doctor about your risk factors for PE. For instance, your risk of PE after surgery is higher if you’re over 40 or if you’re overweight. It’s also higher if you have cancer, are pregnant, smoke, take birth control pills, or have certain other major medical problems^{2, 3}.

One of the highest risk factors is a history of blood clots in you or your family members⁴, so be sure to tell your surgeon about any history of clotting problems. Having a good sense of your risk helps your surgeon to plan the appropriate degree of protection that you should get.

And of course, if you are already taking a blood thinner because of clots in the past, it is extremely important that your surgeon know about that before planning your operation.

Optimize your health. A regimen of walking, minimizing or quitting smoking, and maintaining a balanced diet before surgery can reduce your risk of many complications, including blood clots.

What You Can Do After Your Operation to Help Prevent Pulmonary Embolus

Take preventive medicines (if prescribed): If you go home the same day as your operation, chances are you won’t need any medication to prevent blood clots. But if you have an operation that requires a hospital stay, your surgeon may prescribe a medicine to reduce your risk of developing a DVT or PE. The most common medication used for this is called heparin. It is delivered by injection under the skin, two or three times a day, just while you’re in the hospital. The shots aren’t painful, but can leave bruises at the injection sites (usually on your abdomen). It’s important to get the heparin shots to reduce your risk.

In some cases, particularly if you are having surgery for cancer or morbid obesity, your doctor may prescribe a longer-acting heparin product, called a “low molecular weight heparin.” These are injected once or twice per day, and unlike regular heparin, you may go home with shots to inject for up to a month after your operation. Your nurses and pharmacists will teach you and your support team how to do the shots at home…it’s very easy and the needles are tiny.

Get up and walk. While you’re stuck in bed after an operation, your medical team may have you wear squeezing boots called “sequential compression devices” (SCDs). These can help keep blood flowing through your legs to prevent clotting, but nothing beats the healing effects of getting up and walking.

Walking not only prevents blood clots, it decreases your risk of post-operative infections and helps you get back to your pre-operative condition faster. Walk early, walk often. Aim for at least three times a day. Get your nurses to help.

How Do You Know if You Have a Blood Clot?

Leg swelling: Some swelling in your legs can be normal after surgery, but one side swelling more than another can be a sign of a DVT keeping blood from flowing out of one of your legs. If you notice one leg becoming more swollen than the other, tell your medical team. The test for DVTs is an ultrasound of the legs, which is not painful, and is quick and fairly accurate.

Shortness of breath: One of the most important signs of a PE is a sudden shortness of breath. If you notice it’s becoming more difficult to breathe after your operation, call your nurse (if you’re in the hospital), or go to the emergency room immediately.

What If You Get a Blood Clot?

DVTs and PEs are usually treated with medication, which involves taking blood thinners for at least six months. Most people start with a higher dose of the same injectable heparin used to prevent clots, then move to a pill form called warfarin or Coumadin after a few days.

In rare cases, clots are removed with surgery or a filter is placed in the veins by interventional radiologists to catch clots as they move to the lungs. These procedures are only necessary for a small percentage of patients.

Disclaimer: Keep in mind that the information in this blog is not intended to be medical advice. It’s important to follow the instructions and guidance of your doctor and healthcare team, which might be different than the information provided here.

This story originally appeared in the  Health Dialog Care Compass Blog.