Many cases of the blood clotting condition deep venous thrombosis (DVT) can be linked to recent hospitalisation, landmark research published last night has found.
Doctors from the University of Massachusetts and McMaster University, Ontario, examined the medical records of 1,900 people with a confirmed episode of venous thromboembolism, including DVT and pulmonary embolism (PE) - a clot that travels to the lungs. They found that clots occurred three times more often to outpatients than to people who were inpatients and that almost half of the outpatients with deep vein and lung clots has recently been hospitalised.
"In all, 73.7 per cent of patients developed venous thromboembolism in the outpatient setting: a substantial proportion of these had undergone surgery (23.1 per cent) or hospitalisation [ for a medical illness] (36.8 per cent) in the preceding three months," the authors say. Published in the US medical journal, Archives of Internal Medicine, the study challenges the widely held assumption that DVT and PE occur most often to patients while they are in hospital. And it points to a need to adopt a more proactive approach to clot prevention, not just in hospital, but also following a patient's discharge.
In an accompanying editorial, Dr Samuel Goldhaber, of the Brigham and Women's Hospital, Boston, notes that around half of those developing a clot did so following a hospital stay of less than four days. "We must prospectively 'immunise' hospitalised patients with venous thromboembolism (VTE) prophylaxis because it will not be possible to determine during the short hospital stay which patient will subsequently develop acute VTE," he states.
However, the Massachusetts research found that less than half of the patients who developed a leg or lung clot had received preventive treatment during their hospitalisation. The authors suggest that even patients in hospital for a short time should be given preventive therapy. Proven methods include the use of compression stockings, pneumatic compression devices and anticoagulant drugs.
Previous research has shown that patients given anticoagulant treatment prophylactically experienced a 57 per cent reduction in PE and a 53 per cent reduction in DVT. Administering the anticoagulant heparin at a dose of 5,000 units three times a day has been shown to be effective.
Most clots that develop in the deep veins of the leg or pelvis do not break off and travel to the lung. However, those that do can cause serious damage to the lungs and may be fatal; it is estimated that as many as 10 per cent of hospital deaths can be attributed to pulmonary embolism. But in the absence of a post mortem, many cases of acute PE are ascribed to an acute heart attack.
As well as prolonged immobilisation - including long distance travel - other risk factors for developing DVT include active cancer, dehydration, smoking and pregnancy.