Venous Thromboembolism (VTE) Prophylaxis

VTE risk factors
Choice of VTE prophylaxis

A significant number of surgical patients are in a high risk group for developing VTE.  This is because they are old, often have malignant disease, undergo prolonged operations and remain immobilised for considerable period of time postoperatively.

In all surgical patients assess VTE risk and assess bleeding risk. Balance the risks and offer VTE prophylaxis if appropriate. Do not offer pharmacological VTE prophylaxis if patient has any risk factor for bleeding and risk of bleeding outweighs risk of VTE.  Reassess risks of VTE and bleeding within 24 hours of admission and whenever clinical situation changes.

For all patients

• Do not allow patients to become dehydrated unless clinically indicated.
• Encourage patients to mobilise as soon as possible.
• Do not regard aspirin or other anti-platelet agents as adequate prophylaxis for VTE.

For patients having elective surgery

• Oral contraceptives and HRT- stop 4/52 pre-op
• Pre-existing anti-platelet therapy- Assess risks and benefits of stopping pre-existing anti-platelet therapy 1 week before surgery.
• Anaesthesia- consider regional anaesthesia, in addition to other methods of VTE prophylaxis, as it carries a lower risk of VTE than general anaesthesia.

Regard surgical patients and patients with trauma as being at increased risk of VTE if they meet one of the following criteria:

• surgical procedure with a total anaesthetic and surgical time of more than 90 minutes, or 60 minutes if the surgery involves the pelvis or lower limb
• acute surgical admission with inflammatory or intra-abdominal condition
• expected significant reduction in mobility
• one or more of the following risk factors

VTE risk factors

• Active cancer or cancer treatment
  
• Age > 60 years
  
• Critical care admission
  
• Dehydration
  
• Known thrombophilias
  
• Obesity (BMI > 30 kg/m2)
• >1 significant medical comorbidity
  
• Personal history or first-degree relative with a history of VTE
  
• Use of HRT or Use of oestrogen-containing contraceptive therapy
  
• Varicose veins with phlebitis

Choice of VTE prophylaxis

• Base the choice of mechanical VTE prophylaxis on clinical condition, surgical procedure and patient preference. Choose any one of:
  • anti-embolism stockings (thigh or knee length)
  • foot impulse devices
  • intermittent pneumatic compression devices (thigh or knee length).
• Base the choice of pharmacological VTE prophylaxis on local policies, clinical condition (for example, renal failure) and patient preference.

Offer mechanical prophylaxis at admission to patients who have GIT surgery and have a high VTE risk. Continue until mobility no longer significantly reduced. Add fenoxaparin (Clexane) (or UFH) if the risk of bleeding is low. If patients have major cancer surgery of pelvic surgery pharmacologic prophylaxis should be continued for 28 days.

Remember to screen any postoperative patient with sudden onset of dyspnoea or chest pain for deep venous thrombo-embolism if no atelectasis or pneumonia is detected to account for the patient’s symptoms.  Usual investigations would be clinical examination, CXR, arterial blood gases, ECG, groin U/S or Doppler venous examination and perfusion scan if the suspicion is high.  If the suspicion is high enough, treatment of DVT should be started before confirmatory test results are available.  Contact your registrar.  

The management is supplemental oxygen, intravenous bolus of 5000 units of unfractionated heparin and a heparin infusion consisting of 200 mls of normal saline with 25,000 units of unfractionated heparin.  Start at a rate of 10 ml / hour (10 drops / min if drip set is 60 drops/ml) via an IVAC. Check PTT after 6 hours.  Readjust the rate depending on the PTT results as follows:

If DVT is confirmed, commence warfarin 48 hours after starting heparin.  When heparin is continued for more than a week, check the platelet count (heparin induced thrombocytopenia).