Clots in the lungs

Posted November 23, 2009 10:40:00

Dr. Philip S. Chua

Cebu Daily News

How do clots get to the lungs?

The commonest sources of blood clots in the lungs are the veins in the pelvis and in the legs, where the clots form and travel to the lungs. This condition is called pulmonary embolus or PE, for short, where clots are “filtered” and caught in the pulmonary artery (the main artery of the lungs), causing obstruction of blood flow into the lungs, resulting in hypoxia (diminished oxygen blood level). Pulmonary embolus is a serious condition which could be fatal, if not detected and treated promptly.

How prevalent is it?

In the United States, more than 650,000 cases of PE are diagnosed each year, making it the third most common causes of death. It also ranks as the first or second most common causes of unexpected death in most age groups. Sixty percent of hospitals deaths among patients admitted and treated for other illnesses were found to have PE on autopsy. The diagnosis of PE is usually missed in 70 percent of cases because of the subtle and treacherous nature of the condition.

Which patients in the hospital are prone to have PE?

The likely target of PE are as follows: those medical patients placed on bed rest for at least a week (10-13 percent of them are prone to develop PE); patients in medical ICU (29-33 percent); patients with lung disease on bed rest for 3 or more days (20-26 percent); post-heart attack patients in Coronary Care Unit (27-33 percent); and, those patients with no symptoms, recovering in the hospital after coronary bypass surgery (48 percent). Because of this fact, early ambulation is encouraged among these patients, and most, if not all, are placed on blood thinner of one form or the other, to prevent blood clots and PE.

Is the condition dangerous?

Very, in severe cases. It could even be life-threatening. What happens is the pulmonary artery becomes filled with blood clots and eventually blocked off. This will prevent much of the blood from going to the lungs to be oxygenated. As a result, the person’s blood oxygen level drops dramatically (hypoxia), a condition that could lead to severe shortness of breath, massive chest pains, shock and cardiac arrest.

Are there mild forms of PE?

Yes, when the blood clots lodged in the pulmonary artery are small ones and not significantly blocking the blood flow to the lungs. Mild, sub-clinical PE, those without symptoms where persons are not even aware they have blood clots in the lungs, occurs much more commonly than we realize. Many times, the discovery of PE is made during autopsy. Normally, the lungs automatically lyse (dissolve) blood clots, but if the clots are very large and overwhelming, the enzymes will not be able to dissolve the clots and the dangerous situation described earlier will come into play.

Why do clots form in the legs and pelvis?

The most common reason is the presence of varicose veins in the legs and in the pelvic veins, where blood pools and stagnate. This slowed circulation and stagnation promotes thrombosis (clot formation). If the clots are not firmly attached to the walls of the veins, normal body movement could send these clots flowing with the stream of blood, all the way to the pulmonary artery and to the lungs.

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