Blood normally flows continuously without clotting. Immobility is the chief cause of leg vein clots, which can loosen and fly to the lung. Loose clots are called “emboli,” the Greek name for plugs. Prolonged travel, lying anesthetized on an operating table for surgery, or prior damage to the veins can interfere with the free flow of blood and cause clots that can endanger life. The large clots usually form in the legs, particularly in the thigh region, and may break off and block blood to the lungs. Smoking, cancer, and some hereditary blood clotting problems add to the danger.
Smaller clots that go to the smaller vessels of the lungs often remain undiagnosed for years. Of all the acute diseases, clots to the lung are the most undiagnosed.
Humankind was meant to be mobile. That is one of the best protections against clot probabilities and their sequela. When traveling also remember to get up from your seat every hour on long distance airplane trips and at least walk the length of the aisle a couple of times. Massage will stimulate the flow of stagnant blood in leg veins too.
About a quarter of unprotected patients with hernia operations, a third of patients with heart attacks, and half of people with hip operations or prostate operations have clots move to the lungs. Most of them are small. Fortunately, physicians are now aware of this and take protective action.
Protection against clot formation in the legs after surgery is designed to prevent blood pooling in the legs by getting the patient up shortly after surgery, or the use of elastic or pneumatic stockings. Alternatively, it can be chemical, with the use of blood thinning drugs. Patients given heparin injections after an operation are eight times less likely to form clots than those without this treatment.
Patients with unexplained rapid breathing, rapid heart action, or fainting after operations will need study. The usual investigation is x-ray pictures of the lung showing the distribution of inhaled radioactive gas and radioactive albumin particles given intravenously. A “mismatch” on the x-ray means that part of the lung that has radioactive gas does not have the radioactive solution in the vessels. A mismatch therefore means clots in the lung. In contrast, pneumonia and chronic lung disease will change the distribution of both radioactive materials.
Unfortunately, about 20% of people who have clots in their lungs don’t have swelling in their legs as an early clue. In some patients, the lung scan does not give a clear diagnosis and, in such cases, a diagnosis can be made by an angiogram or x-ray of blood vessels in the lungs with an opaque solution used with x-rays injected through a catheter threaded into the main artery to the lungs.
More and more surgeons and internists are using prophylactic blood thinning in people subjected to prolonged inactivity, especially elderly or obese patients who tend to move less. A summary of 30 trials with and without heparin blood thinner in 16,000 patients showed that the anticoagulant reduced emboli going to the lung by more than half and deaths by two-thirds. Oral warfarin (another blood thinner) is not usually given unless heparin prophylaxis is unsuccessful. Ten percent of people with pulmonary emboli die within the hour and later one-third more die.
DISCLAIMER: The information provided here is for general informational purposes only, and is provided as a supplement for students enrolled in Meditec’s medical career training courses. The information should NOT be used for actual diagnostic or treatment purposes or in lieu of diagnosis or treatment by a licensed physician.