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PULMONARY EMBOLISM - VENOUS THROMBOSIS

What is a Pulmonary Embolism ?

A thrombosis is a blood clot which usually causes a blockage of a blood vessel. In the veins it is called a venous thrombosis. It is commonest in the legs, where there are superficial veins beneath the skin and deeper veins below and between the muscles. Thrombosis in the deeper veins (deep vein thrombosis) is more serious, although it probably happens frequently without symptoms. It may cause an aching or cramp-like pain, especially in the calf on walking. There is often swelling of one foot or ankle because fluid is forced out of the blood vessels. Part of the blood clot may break free (an embolism) and travel through the circulation to the lungs. This is a pulmonary embolism. It may cause chest pain, a cough, or sudden breathlessness. The sputum may become bloodstained. A large embolism may obstruct the circulation causing breathlessness and dizziness. If it is big, it may even be life threatening. If the thrombosis occurs in a superficial vein, there may be reddening and soreness of the skin (thrombophlebitis). Embolism is only rarely seen after thrombosis of a superficial vein.

How does a Pulmonary Embolism occur ?

Venous thrombosis may occur when blood flow through veins is sluggish, when there is pressure on, or injury to such a vein and when there is increased tendency to blood clotting. Sometimes it happens for no clear reason. It is a little commoner with the contraceptive pill which may affect blood clotting slightly.

Why does a Pulmonary Embolism occur ?

It can happen at any age, and is common in those who are bed-bound or have heart failure, or after operations, when blood clots more readily and the blood flow is reduced. It may also happen after a long airline flight or long bus trip because the blood circulation in veins is slowed down by prolonged sitting. One to two percent of the population have reduced levels of certain proteins (C and S) in the blood and a few have antibodies to a substance called phospholipid. These people appear to be more prone to more severe and recurrent thrombosis. People who have cancers are also more prone to venous thrombosis. Sometimes such a blood clot is the first sign of an underlying malignancy. The exact reason why an embolism occurs in some people with a thrombosis is not clear. It is probably more common with large thromboses.

Treatment Involved for a Pulmonary Embolism

DIAGNOSIS Tests may be done to check if there is an underlying blood abnormality, such as protein C or protein S deficiency. An excessive number of either red blood cells or of platelets (which are responsible for the "stickiness" of blood) can also predispose to clotting. Deep vein thrombosis is usually diagnosed on a simple medical examination. If there is doubt, an x-ray of the veins (venogram) can be taken. Ultrasound (Doppler) scanning of the veins is also very useful. For detecting pulmonary embolism, the simplest methods are chest x-rays and electrocardiograms. The clot in the lung can be shown either by CT scanning, injecting x-ray dye into the lung circulation through a vein (pulmonary angiogram) or by using a scan. These lung scans use small quantities of radio-isotopes injected into the circulation to show the disturbed blood flow in the lungs.

TREATMENT Treating a deep vein thrombosis involves big doses of heparin, given over several days through a drip into a vein whilst the patient is admitted to hospital. This treatment is also used for a pulmonary embolism. After a few days, heparin is usually changed to an anticoagulant given by mouth, usually warfarin. There are difficulties with its use. Different people require different doses which are adjusted according to need. This is done by testing the ability of the blood to clot. Because it takes 24-36 hours before a particular dose has its full effect, this blood testing must be delayed after each dose change. Repeated blood tests are essential until the dose is right. Eventually the blood tests can be reduced to once per month. After a thrombosis, a properly fitting elastic stocking should be worn and the leg elevated when sitting down. This may need to be continued for some months. Pulmonary embolism is usually not serious, but can occasionally be fatal. Heparin, and then warfarin are used, as for a vein thrombosis. Warfarin is usually continued for at least six weeks. Sometimes thrombosis and embolism recur repeatedly, particularly with underlying blood abnormalities. Warfarin is then continued for longer. If embolism is more serious, the clots must be dissolved. For this, drugs called thrombolytics are given intravenously or through a catheter passed into the main lung artery. If pulmonary embolism threatens life, operations sometimes have to be performed to remove the blood clot.

PREVENTION is better than cure! Drugs called anticoagulants can prevent deep vein thrombosis. Heparin is one of them and it is injected under the skin in patients who are either at risk or restricted to bed. This is now routine following a heart attack and after many types of surgery. Until recently this could only be done in hospital; newer so-called low molecular weight heparin can now be given once per day on an out-patient basis. During long operations, surgeons take great care to avoid any pressure on the calves which might damage the veins and lead to a thrombosis. In a prolonged journey, or even with a prolonged hospital admission, people are urged to move their legs often and to change position as frequently as possible. Sitting for a long period, as on an aeroplane, is not natural. Regular walks down the aisle and ankle exercises whilst sitting, help to avoid venous thrombosis. Dehydration is also a factor. This is aggravated by drinking alcohol and avoided by taking lots of water based drinks.

During Treatment for a Pulmonary Embolism

Anticoagulants and thrombolytics may cause bleeding. This is a particular risk if the patient has had a stomach ulcer or a previous bleed. It may also happen from wounds, following very recent operations, injuries, and after strokes. You must keep a lookout for bleeding problems. Minor cuts usually only bleed a little more than usual. It is important to avoid drugs like aspirin, which may also cause bleeding. Many drugs upset the warfarin dose and must not be given without careful extra testing of clotting and adjustment of dose. These include antibiotics anti anti-inflammatory drugs. Alcohol upsets anticoagulation and should only be taken regularly in moderation. All patients taking anticoagulants by mouth should carry a card with details of blood tests and the drug dose.

After Treatment for a Pulmonary Embolism

Most people can forget about the problem after anticoagulants are stopped. Some have a tendency for blood dots to come back. Any leg pain, ankle swelling, chest pain, or cough needs to be notified to the doctor if it occurs. It is best to avoid the contraceptive pill.

If a Pulmonary Embolism is Left Untreated

Most deep vein thromboses would probably cure themselves: extra channels open up for returning blood from the tissues. Without anticoagulants, the risk of pulmonary embolism would be greater. Once an embolism has occurred, the likelihood of a further (and more serious one) would also be higher.

Effects on Family of a Pulmonary Embolism

Provided your treatment is carefully monitored, it should not affect your life nor those of family or friends. If you are on anticoagulant, try to avoid activities which risk an accident - you might bleed seriously.