Everything You Need to Know about Deadly Blood Clots

John Fisher
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Stopping Medical Injustice

How Blood Clots Kill

Blood clots may form when blood fails to flow properly.  Prolonged immobilization can reduce blood flow to the legs, increasing the risk for blood clots in the leg veins (deep venous thrombosis or "DVT"). The main cause of DVT is poor blood flow.

When a blood clot is large enough to reduce the blood flow to a tissue, hypoxia (oxygen deprivation) can occur and metabolic products such as lactic acid can accumulate.  A larger blood clot causing a much greater obstruction to the blood flow can result in anoxia, which is the complete deprivation of oxygen and infarction and tissue death. Thromboembolism is the combination of a blood clot (thrombus) and its main complication, embolism. 

If a blood clot breaks free and travels to your lungs, it is called a pulmonary embolism and it can be fatal.  Patients with a DVT are at high risk of developing a pulmonary embolism. Pulmonary embolism can be life threatening because the body's oxygen supply can be cut off. Untreated acute deep venous thrombosis causes pulmonary embolism in 33-50% of patients and mortality in untreated pulmonary embolism is approximately 30%. Death from DVT-associated massive pulmonary embolism causes as many as 300,000 deaths annually in the United States.

The Risk Factors for Deep Venous Thrombosis

Blood clots can be caused by anything that prevents your blood from circulating normally or clotting properly. Most hospital inpatients are at risk of DVT.

Many factors increase your risk of developing deep venous thrombosis, including:

  • Sitting for long periods of time, such as when driving or flying,
  • Prolonged bed rest, such as during a long hospital stay or paralysis. When your legs remain still for long periods, your calf muscles don't contract to help blood circulate, which can make blood clots develop,
  • Injury or surgery. Injury to your veins or surgery can slow blood flow, increasing the risk of blood clots. General anesthetics used during surgery can make your veins widen (dilate), which can increase the risk of blood pooling and then clotting,
  • A history of deep vein thrombosis or pulmonary embolism.  If you've had deep venous thrombosis ("DVT") before, you're more likely to have DVT in the future,
  • Being overweight or obese.  Being overweight increases the pressure in the veins in your pelvis and legs,
  • Smoking. Smoking affects blood clotting and circulation, which can increase your risk of DVT,
  • Being tall.  Taller men may be more likely to have blood clots.  Taller women do not appear to have an increased risk, perhaps because women do not get as tall as men.

What are the Symptoms of DVT?

DVT can cause damage and even death within hours. The symptoms of DVT may include:

  • Swelling in one or both legs,
  • Pain or tenderness in one or both legs, which may occur only while standing or walking,
  • Warmth in the skin of the affected leg,
  • Red or disclored skin in the affected leg.

The Best Way to Prevent Deep Venous Thrombosis and Pulmonary Embolism

Treatment of DVT is aimed at preventing the extension of the DVT and embolization.  Anticoagulation therapy (blood thinning medication) remains the mainstay of medical therapy for DVT because it is non-invasive, it treats most patients (approximately 90%) with no immediately demonstrable physical sequelae of DVT, it has a low risk of complications and the data show an improvement in morbidity and mortality.  Blood clot prevention and treatment reduces the risk of stroke, heart attack and pulmonary embolism.  

For more than 20 years, routine preventative anticoagulation therapy has been the standard of care for major orthopedic surgery. Thrombosis (blood clot), especially in the deep veins of the leg, is a particular danger after major surgery. High risk surgical procedures include neurosurgery and major orthopedic surgery of the leg, such as a hip or knee replacement.  Early prophylaxis in surgical patients with low molecular weight heparin (LMWH) has been associated with significant reductions in the postoperative formation of blood clots.  The American College of Chest Physicians (ACCP) recommends that low molecular weight heparin (LMWH) be given to patients undergoing major orthopedic procedures at least 12 hours preoperatively or postoperatively.

Pneumatic compression stockings in cardiac surgery and neurosurgical patients have shown a distinct improvement in the incidence of DVT without the added risk of bleeding.

Have Questions?

If you have questions about deep venous thrombosis or pulmonary embolism, we will be happy to speak with you. You can call us at 518-265-9131.