Prevention of Deep Vein Thrombosis

Clinicians are frequently asked to advise patients on prophylactic measures to minimise the risk of venous thromboembolism. NICE has produced guidelines to assist in reducing the risk prior to inpatient surgery,¹ but there are other clinical scenarios which need to be considered (e.g. air travel).

• NICE state that approximately 30% of surgical patients develop deep vein thrombosis (DVT).
• The condition is frequently asymptomatic but can lead to sudden death due to pulmonary embolism.
• The risk of fatal embolism after high risk surgery is1-5%.¹

The following surgical procedures are high risk:¹

• Orthopaedic surgery (for example, total surgery for hip fracture)
• Major general surgery
• Major gynaecological surgery (but not caesarean)
• Urological surgery (including major or open urological procedures)
• Neurosurgery
• Cardiothoracic surgery
• Major peripheral vascular surgery

See related articles:

• Thrombophilia
• Pulmonary Embolism
• Deep Vein Thrombosis

Patients should be assessed individually for risk factors for venous thromboembolism (VTE).

All patients prior to inpatient surgery

• Patients on oral contraceptives should be advised to consider stopping four weeks before elective surgery.
• Immobility associated with continuous travel of more than three hours in the four weeks before surgery should be avoided.
• Verbal and written information should be given on the risks of VTE and any prophylactic measures that should be taken to avoid it.
• Prior to discharge, patients should be given verbal and written information on
  • Signs and symptoms of deep vein thrombosis and pulmonary embolism
  • Correct use of prophylaxis at home
  • Implications of not using prophylaxis correctly

High risk patients

High risk patients should be offered:

• Mechanical Prophylaxis
  
  Several methods are available.
  • Thigh-length graduated compression /anti-embolism stockings can be used unless contra-indicated (e.g. in patients with established peripheral arterial disease or diabetic neuropathy). If thigh-length stockings are not appropriate (for reasons of fit or compliance) knee-length stockings may be used instead.
    • The stocking compression profile should be equivalent to the Sigel profile (a pressure profile for elastic stockings), and approximately:
    • 18 mmHg at the ankle
    • 14 mmHg at the mid-calf
    • 8 mmHg at the upper thigh
  • Staff trained in the use of compression stockings should show the patient how to wear them correctly, monitor their use and provide assistance when needed.
  • Patients should be encouraged to wear stockings from admission until they return to their normal level of mobility.
  • Intermittent pneumatic compression or foot impulse devices may be used instead of, or as well as, graduated compression stockings while patients are in hospital. They should be used for as long as practical prior to surgery.
• Pharmacological Prophylaxis
  • Patients with high risk and those having orthopaedic surgery should also be offered low molecular weight heparin (LMWH). Fondaparinux, within its licensed indications, is an effective and safe alternative.²
  • Consideration should be given to the risks and benefits of stopping pre-existing anticoagulation or antiplatelet therapy before surgery
  • The timing of pharmacological prophylaxis if using regional anaesthesia to minimise the risk of haematoma.
• Other Options
  • Patients should be encouraged to maintain their fluid intake and not become dehydrated during their stay in hospital.
  • Regional anaesthesia is to be preferred if possible as it is less of a risk for VTE than general anaesthesia.
  • Vena caval filters should be considered for patients who have existing or recent (within one month) VTE and anticoagulation therapy is contraindicated. These are devices which can be inserted into the inferior vena cava to prevent the development of a pulmonary embolus.
  • Patients should be encouraged to mobilise, or leg exercises should be arranged if they are immobile, as soon as possible after surgery.

Patients with no risk factors

Patients having hip replacement, surgical treatment of hip fractures and other kinds of major orthopaedic surgery should be offered mechanical and pharmacological prophylaxis. Otherwise, only mechanical prophylaxis is required.

Travel-related DVT

At the time of writing, NICE guidance on the prevention of travel-related DVT and other non-surgical scenarios is being developed. In the interim, clinicians should advise patients according to the guidance produced by the Department of Health.³ The DoH state that DVT or pulmonary embolus (PE)occurs every year in about 1-3 in 1000 people in the general population, ranging from less than 1 in 3000 in people under the age of 40 up to 1 in a few hundred in those over 80. 90-95% of travel-related DVT or PE occur in the following groups:

• Over 40 years of age
• Pre-existing thrombosis
• A family history of thrombosis
• Suffering from or who have had treatment for cancer
• With hypercoagulable blood disorders (e.g. thrombophilia)
• Co-existing heart failure and circulation problems
• Recent surgery especially on the hips or knees
• Very tall

DVT is also more common in women who:

• Are pregnant
• Have recently had a baby
• Are taking the contraceptive pill
• Are on hormone replacement therapy or HRT

During the trip, the DoH recommend advising passengers to :

• Get comfortable and recline the seat as much as possible
• Wear loose fitting clothing
• Store hand luggage in the overhead lockers to keep the room under the seat in front free
• Bend and straighten the legs, feet and toes while seated every half-hour or so during the flight
• Press the balls of the feet down hard against the floor or foot-rest to increase the blood flow in the legs and reduce clotting
• Do upper body and breathing exercises to further improve circulation
• take occasional short walks around the cabin, whilst the aircraft is cruising at altitude
• Take advantage of refuelling stopovers where it may be possible to get off the plane and walk about
• Drink a reasonable amount of water
• Avoid alcohol, which in excess leads to dehydration and immobility
• Avoid taking sleeping pills, which also cause inertia

• For people at moderate risk (e.g. women on HRT or the Pill, past history of VTE) consider using compression hosiery
• For people at high risk (e.g. travel-related VTE in the past 5 years; spontaneous VTE in the past 5 years; any VTE in past 1 year) in addition to stockings, seek the advice of haematologist. Consider a single dose of low molecular weight heparin injection 2-3 hours prior to departure and again prior to returning home.
• There is no evidence that addition of aspirin, or increasing existing aspirin dose, has a preventive effect in any high-risk group.