THROMBOEMBOLIC DISEASE

THROMBOSIS AND THROMBOEMBOLISATION

Thrombosis refers to the process in which a mass of clot forms inside an artery or vein. It consists of a dense network of fibrin in which are trapped variable portions of red cells and platelets.

Thrombosis blocks the vessel and impairs blood flow.

Arterial thrombosis leads to ischaemic tissue damage (myocardial infarction, stroke and peripheral vascular disease), whereas in venous thrombosis the consequences are due to back pressure and local swelling (oedema).

If the clot disintegrates, parts of it can break off, producing emboli that travel onwards: in venous thrombosis through the veins to the lungs (pulmonary embolus), and in arterial thrombosis through the arteries to major organs such as the brain (cerebral embolus), limbs (peripheral embolus), kidneys (renal infarction) and intestine (acute bowel ischaemia).

Superficial thrombophlebitis

Thrombophlebitis is a painful inflammation of the superficial veins. Classically it is seen with infected venous cannulae, but it also commonly occurs in patients with varicose veins.

The clinical picture is of palpable and very tender cords of thrombosed and inflamed veins, with the overlying skin appearing reddened or bruised.

Thrombophlebitis is not in itself dangerous, but may accompany deep vein thrombosis.

Management is removing the cause and treating the symptoms.

Deep vein thrombosis (DVT)

Deep vein thrombosis is a more serious problem, because of the risk of fatal pulmonary embolus. Most DVTs start in the deep veins of the calf, termed the distal veins, where they cause local pain and swelling. One in five extend up the leg to involve the proximal veins in the thigh and pelvis (popliteal and iliofemoral thrombosis). The risk of a pulmonary embolus from a proximal vein thrombosis is very high. A significant proportion of the survivors will develop a postphlebitic syndrome in the affected leg, with chronic swelling, varicose veins, skin pigmentation, recurrent thrombosis and venous ulceration.

The management is based on preventing progression of the thrombotic process by using heparin for an immediate effect, followed by warfarin in the medium to long term. The aim of treatment is to stabilise the situation, prevent extension, reduce the chances of embolisation and lower the risk of recurrence.

Critical nursing tasks in suspected DVT

-Give the first dose of heparin immediately.

-Ensure there is adequate pain relief.

-Be vigilant for acute ischaemia.

-Care of the pressure areas.

-Reassure the patient.

-Document all current regular and intermittent medication.

-Document the target INR (usually 2.5).

-Ensure a warfarin loading schedule is followed by the prescribing doctors.

*Other causes of a swollen painful leg: cellulitis or necrotising fasciitis.

Pulmonary thromboembolism

Most pulmonary emboli arise from the proximal veins in the thigh and pelvis. Depending on their size, emboli that travel to the lung either become wedged in the main pulmonary arteries, where they block the outflow of blood from the right side of the heart, or pass onwards to become trapped in the lung peripheries.

-The former, termed massive pulmonary emboli, produce a disastrous decrease in cardiac output, leading to sudden death or acute hypotensive collapse. Massive pulmonary emboli can move or start to break up either naturally or during the course of cardiopulmonary resuscitation. Thrombolytic drugs can help to dissolve the embolus and are used in the unstable hypotensive patient. Heparin will prevent further emboli, and as most patients who survive the first embolus die from a recurrence within the first few hours, it is important to start treatment urgently. Warfarin is added for long-term prevention.

-The smaller emboli in the periphery of the lungs produce wedge-shaped areas of lung damage and give rise to overlying pleurisy. The management of smaller peripheral emboli is based on preventing further and possibly bigger emboli by giving heparin and, subsequently, warfarin.