Pulmonary Emboli
Introduction:
Emboli are blood clots. They usually form in leg veins or in pelvic veins. If you would like a quick primer on what thrombosis is all about, click on this link and click on "All About DVT". Clots happen because a person is particularly vulnerable from a constitutional point of view or because there is a time period such as following surgery, where the blood is thicker and clots happen easier.
Also, certain hormone changes can predispose the person to blood clots. When clots occur in leg veins or pelvic veins, there is a risk that the clots grow in length, finally break off and migrate into the right heart. There they tend to break up and move on into the arteries of the lungs (see how this affects the lung).
This can lead to acute symptoms and in about 10% of the cases is severe enough to close off the circulation to at least a part of the lung (if not all of the lung), which is called pulmonary infarction. When 608clots from the veins in the legs break off and migrate into the lungs pulmonary emboli result. In about 65% this affects both lungs. Due to anatomical differences there is a slight blood circulation advantage to the right lung, so the remainder of the clots, when only one lung is affected, occurs in 25% in the right lung and in 10% in the left lung.
Signs and symptoms:
The onset of pulmonary emboli is usually very acute. There are a variety of symptoms that occur simultaneously. The most striking symptom is an air hunger and rapid deep breathing (dyspnea).
If the clots are massive, the patient may get into shock and become unconscious or may even die. However, this happens only in 1 to 5%. Here are some of the most common symptoms of blood clots. Most of the time there is a slower onset or there is only a partial blockage of the pulmonary arteries, but the patient still needs to be rushed into a hospital by ambulance as quickly as possible. Heparin, which is an anticoagulant medication needs to be started right away to prevent further clot formation. Other clot dissolving medication is also started to get a rapid improvement of the condition as soon as possible. With clots that lead to infarction at the surface of the lung there will be a friction rub that the doctor may hear using the stethoscope and the patient feels pain with every breath due to pleuritic pain. Hemoptysis (coughing up blood or blood stained phlegm) can be another sign as well as wheezing. The patient is usually extremely anxious and restless, which may be in part due to a lack of oxygen in the brain. Other symptoms are listed in the table.
| Symptoms of Pulmonary Emboli (PE) |
| Symptom: |
Frequency: |
| dyspnea |
73%* |
| pleuritic pain |
46% |
| cough |
43% |
| leg swelling |
33% |
| leg pain |
30% |
| hemoptysis |
15% |
| palpitations |
12% |
| wheezing |
10% |
| angina type pain |
5% |
*Note: %-ages do not add up to 100%; symptoms can occur simultaneously |
Diagnostic tests:
A patient with pulmonary emboli needs to be seen and treated in the Emergency Department of a hospital. Several tests need to be done in rapid succession and heparin and clot dissolving therapy needs to be started at the same time.
After an initial quick examination the Emergency Room physician likely will want to do some simple initial tests such as oxymetry on a finger or ear lobe and spirometry. Arterial blood gases likely will also be obtained right away as this is giving the physician a good inital assessment as to how extensive the clots in the lung are. A very low partial oxygen pressure in the blood likely is associated with a lot of clots affecting the oxygen absorption significantly. A chest X-ray and likely will be ordered. The lung perfusion scan is done with radioactive tracer sustances (with the radioisotope technetium 99m) and is probably the most important of the tests. It measures the lack of perfusion in the lung tissue affected by pulmonary emboli. The series of scans depicted under this link show a sequence of normal scans in the upper area. In the lower half of the link abnormal perfusion scans demonstrate a large pulmonary embolus in the right lung of this patient.
Another type of lung scan, the ventilation lung scan, uses the inhaled gas xenon-133, which measures the air flow into the lungs. When the lung perfusion and the lung ventilation scans are done simultaneously, the result shows by way of subtraction where a perfusion defect is located. The corresponding lung tissue, which is now blocked by clots from receiving blood from the affected lung artery branch, is still ventilated normally in this area, except in the 10% where a lung infarction has developed (see images). That's why about 90% of the cases with pulmonary emboli can be diagnosed this way with confidence, which is considered to be a very reliable test. For the remaining difficult cases where clinically the patient appears to have pulmonary emboli, but the imaging studies do not clearly show the clots in the lungs, the physician may want to consider a pulmonary arteriogram(or angiogram) to show an arterial filling defect where the clot is located. Further tests such as CT scans, spiral CT scans, and MRI scans can be done to get more details as well, if the extent of the clots needs to be determined.
Treatment:
Treatment depends on the clinical presentation and the finding of the tests in a particular patient. However, generally speaking a form of clot dissolving treatment (thrombolytic therapy) is chosen.
There are rapidly dissolving therapies such as streptokinase and plasminogen activating (t-PA) substances. Then there is clot prevention therapy utilizing heparin initially and a few days later a switch to oral medication such as warfarin. Exact protocols have been developed to standardize the treatment and to avoid overtreatment, which would be thinning the blood too much and cause major bleeding in various areas (brain hemorrhage, seriously bleeding ulcers etc.). With deep vein thrombosis following surgery often the patient will be treated with warfarin for extended periods such as 3 to 6 months to avoid a recurrence of clots. People with atrial fibrillation who have an ongoing risk for blood clots may have to stay on warfarin lifelong.
The newest development in treating pulmonary emboli and other clots is by way of the use of low molecular weight heparins. Various commercial preparations are avilable (Dalteparin, Enoxaparin, Nadroparin and Tinzaparin are pharmacological names). They all have different brand names as well. The dosage is different for each product as the metabolic half-life is different for each product.
However, it is now recognized by the medical profession that these low molecular heparins are very safe and very effective. The advantage is that they work very quickly in dissolving the clot. Once the patient has been started on it and the doctor knows whether the patient tolerates it and how it thins the blood, no further tests for monitoring have to be done. With regular heparin in the hospital setting or Coumadin in the home setting blood tests have to be done frequently to check the degree of blood thinning. The disadvantage is that the patient has to inject a little needle with the low molecular weight heparin into rotating spots of the skin on a regular basis (e.g. twice per day). Small amounts of aspirin can also be combined with low molecular weight heparin (Ref. 10).
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