SIGNÍs recently published guideline on prophylaxis of venous thromboembolism was prompted by research that indicated that 56% of patients who suffered a fatal pulmonary embolism in Scotland in 1995 had not had antithrombotic prophylaxis.
Much of the guideline relates to hospital practice, but as patients are being discharged increasingly early GPs are becoming more involved in prevention of venous thromboembolism. The guideline therefore offers GPs some useful pointers through the difficult clinical maze that this condition presents. It indicates which types of patient are at risk and the relative risk ratios and offers a review of strategies to minimise risks to patients. The quick reference guide is particularly useful for busy GPs.
Already, as a primary measure, we administer aspirin for its cardiac effects in patients following myocardial infarction; the guideline recommends this should be continued and combined with thrombolytic therapy.
Asymptomatic deep venous thrombosis occurs in up to 50% of cases of acute hemiplegic stroke. Aspirin is recommended in cases of ischaemic stroke. The guideline points to the need for brain imaging to exclude intracranial haemorrhage, but I wonder if this can be done sufficiently promptly in todayÍs busy NHS.
Low dose heparins should be considered for any medical patient who is immobilised, a recommendation that may need to be taken on board by GPs treating community hospital patients. It is disappointing, however, that there are no recommendations for prevention of venous thromboembolism in immobile patients resident in care homes.
Some sections of the guideline relate specifically to women. Doctors are reminded to assess the risk of venous thromboembolism in all pregnant patients, which includes taking a family history. For most high risk pregnancies, low dose heparins should be the mainstay of prevention. Treatment should be continued until after delivery and then, if necessary, replaced with warfarin.
Advice as to the small increased risk of venous thromboembolism should be given to women taking the combined oral contraceptive and HRT. The guideline reminds doctors of the contraindications to their use and the increased risk to such women during surgery.
The topical question of long haul air travel is addressed. Sadly, the evidence base is weak but the guideline suggests advising long distance travellers to drink plenty of water, to restrict their intake of coffee and alcohol and to carry out simple leg exercises. For patients at high risk, such as those with a history of venous thromboembolism, recent trauma or surgery and pregnant women, measures to consider include wearing graduated compression stockings or taking a single aspirin or having a single low dose heparin injection before travel.
The guideline emphasises the importance of using low dose heparins for most surgical patients where there are no contraindications. In orthopaedic patients heparins can be used, but the drug of choice is aspirin at 150mg per day for 35 days post-operatively. These recommendations may have some implications for primary care, with community nurses being asked to administer heparin. The guideline recommends regular platelet checks for patients on heparin. Graduated compression stockings and early mobilisation are universally recommended for surgical patients, while oral anticoagulants and other medications have roles in particular situations.
The guideline emphasises the need for GPs to be aware of the risk factors for venous thromboembolism and to offer advice and appropriate preventive measures to patients.
SIGN 62. Prophylaxis of Venous Thromboembolism – a national clinical guideline may be downloaded free of charge from the SIGN website: www.sign.ac.uk