Memorandum by the Department of Health
(VT 14)
INTRODUCTION
1. The Government welcomes this opportunity
to set out the existing position on the prevention of venous thromboembolism.
2. Deep vein thrombosis (DVT) of the lower
limbs is a common disease, often not noticed by the affected person,
but presenting with clinical symptoms (leg pain or swelling) in
about one per 1,000 people per year in the general population.
3. Deep vein thrombosis (DVT) may occur
in about 30% of surgical patients and is commonly without symptoms.
However, the condition can lead to sudden death due to pulmonary
embolism (clot in the lung), or cause long-term effects on health
due to venous ulceration and development of residual pain and/or
swelling in the limb. Pulmonary embolism (PE) following lower
limb deep vein thrombosis is the cause of death in 10% of patients
who die in hospital.
4. Put simply, the condition is one of blood
clot formation in veins of the leg (the "thrombo" part
of the name). This has a risk of clot becoming detached (the "embolism"
part), passing through the blood vessels to the heart and thence
to the blood vessels to the lungs. Once in the blood vessels of
the lung (pulmonary embolism (PE), the clot can block blood flow,
impede the output of the heart, and prevent the adequate exchange
of oxygen and carbon dioxide by the lungs. It is this embolic
feature of the disorder which causes the serious effects such
as death.
5. Most thrombi occur in the deep veins
of the legs. Formation of thrombi is associated with inactivity
and high-risk surgical procedures. The risk is particularly high
in patients undergoing orthopaedic surgery and lengthy operations.
6. Deep vein thrombosis (DVT) has multiple
causes, but the main risk factors are: surgery; age; obesity;
varicose veins; previous venous thromboembolism; genetic and other
blood disorders leading to increased tendency to blood clotting
(thrombophilias); acquired causes of increased clotting such as
the presence of malignant tumours elsewhere in the body; hormone
therapy; pregnancy; immobility; hospitalisation; prolonged travel.
7. Pulmonary embolism (PE), which in 90%
of cases results from an asymptomatic deep vein thrombosis (DVT),
may present as sudden death, breathlessness, faintness, collapse,
or chest pain.
8. About 10% of hospital deaths (1% of all
admissions) were attributable to pulmonary embolism (PE) in the
UK in one study from the 1980s. More recent studies have continued
to highlight the significant contribution of pulmonary embolism
(PE) to in-hospital deaths, especially after emergency surgery
when prophylaxis is often omitted.
9. This memorandum summarises existing NHS
preventive interventions in respect of venous thromboembolism,
existing and planned guidelines, and some key recent high profile
issues.
MAIN PREVENTION
MEASURES IN
PLACE WITHIN
THE NHS—FOR
EXAMPLE, POST-SURGERY
General measures
Mobilisation, leg exercises and adequate hydration.
Mechanical methods
Graduated elastic compression stockings (GECS).
Intermittent pneumatic compression.
Main Pharmacological (Drug) Agents
Antiplatelet pharmacological agents (eg aspirin).
Unfractionated and low molecular weight heparins.
Oral anticoagulants.
Dextrans.
Clinical practice varies, however, and it is
estimated that four out of 10 orthopaedic patients do not receive
any form of prophylaxis (source NICE Guidelines Scope).
PROMOTING BEST
PRACTICE: AVAILABILITY
OF PROTOCOLS
AND GUIDANCE
10. The National Institute for Clinical
Excellence (NICE) has commissioned the National Collaborating
Centre for Acute Care to develop a clinical guideline on the prevention
of venous thromboembolism for use in the NHS in England and Wales.
In the draft scope of this guideline, adult patients who are at
a high risk of developing venous thromboembolism, but are not
undergoing surgery will not be covered. However, the scope is
currently out to consultation and may thus be modified. The expected
date of issue of this guideline is given as May 2007.
11. The British Thoracic Society have issued
authoritative guidelines on the detection and management of the
pulmonary embolism[1]the
main complication from venous thromboembolism. These were issued
in June 2003.
12. Other Guidelines have been produced
by the Scottish Intercollegiate Guidelines Network (SIGN) in 2002.
13. The National Electronic Library for
Health makes these guidelines available to clinicians via their
web-site.
RECENT CONCERNS
AROUND THROMBOEMBOLISM
14. Although there are a wide range of risk-factors
for thromboembolism, two which have been of concern recently are
set out below in more detail (these details are provided from
the SIGN Guideline).
Oral contraceptives
The background rate of spontaneous venous thromboembolism
(VIE) in healthy women who are not pregnant and who do not use
the combined oral contraceptive (COC) pill is around five cases
per 100,000 women per year. The risk is increased threefold (15/100,000
women per year) in users of second generation contraceptives,
and six fold (30/100,000 women per year) in users of third
generation oral contraceptives.
The absolute risk of thrombosis in women taking
third generation pills is small (an excess risk of 10-25
cases of VTE per 100,000 women years) and is less than
the risk associated with pregnancy (estimated at 100 cases
per 100,000 maternities). However, the risks are higher
during the first year of use, approaching 30 per 100,000 women
per year for users of third generation COC. The risk is also much
higher in women with thrombophilias.
Long Distance Travel
There are many published anecdotal reports which
link venous thromboembolism with prolonged travel, particularly
air travel, but there are only three published case-control studies,
and some studies of consecutive patients which are small, prone
to bias, and gave contrasting and imprecise results.
The risk appears higher in patients with known
risk factors and with flights over 3,000 miles.
Possible mechanisms include: immobility; cramped
position; dehydration (augmented by drinking alcohol and coffee);
compression of calf (popliteal) veins by edge of seat; and seated
posture, especially when sleeping. Research findings demonstrate
that the relative risk remains to be established in further case-control
studies, and the absolute risk remains to be established in large,
prospective studies.
Small trials have observed reductions in the
incidence of symptomless DVT by Graduated Elasticated Stockings
(GECS). Stockings used in hospital are designed for use in recumbent
patients and are not suitable for use in flight. Patients should
be provided with the correct type and size of stocking, and should
be instructed how to wear them correctly. Stockings also reduce
leg oedema after long flights. They may precipitate superficial
thrombophlebitis in people with varicose veins.
One small trial observed reduction in the incidence
of symptomless DVT by a single dose of heparin two to four hours
before flight, but not by aspirin (400 mg daily for three days,
starting 12 hours before flight).
Long Distance Travel Guidelines
Recent guidelines for travellers (issued by
the Scottish Intercollegiate Guidelines Network (SIGN)) include:
To minimise the risk of thrombosis when travelling
long distances (eg over four hours), especially by air,
all travellers should be advised to:
— restrict alcohol and coffee intake;
and
— regularly carry out simple leg exercises
and take occasional walks during travel.
In patients at high risk of thrombosis (eg previous
deep vein thrombosis or pulmonary embolism; known blood disorders,
such as thrombophilia; recent major trauma, surgery or immobilising
medical illness, pregnancy), the following prophylactic methods
should be considered:
Graduated elastic compression stockings (GECS):
— a single dose of aspirin (150 mg)
before travel (±GECS);
— a single injection of a low molecular
weight heparin before travel in prophylactic dose (±GECS);
and
— patients already receiving warfarin
should continue to take it (±GECS). INR should be checked
one week before long-distance travel and the dose adjusted to
within the target therapeutic range.
SOURCES AND
WEB-LINKS
National Electronic Library for Health
http://libraries.nelh.nhs.uk/guidelinesFinder/viewResource.
asp?uri=http://libraries.nel h.nhs.uk/common/resources/?id=30462
National Institute for Clinical Excellence
http://wwvv.nice.org.uk/page.aspx?o=63366
British Thoracic Society Guidelines
http://www.brit-thoracic.org.uk/docs/PulmonaryEmbolismJUNO3.pdf
Scottish Intercollegiate Guidelines Network
http://www.sign.ac.uk/guidelineslfuffiext/62/index.html
1 British Thoracic Society guidelines for the management
of suspected acute pulmonary embolism British Thoracic Society
Standards of Care Committee Pulmonary Embolism Guideline Development
Group. Thorax (2003); 58:470-484. Back
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