Anticoagulation and VTE risk

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COVID 19 pneumonia is a highly thrombogenic condition with increased prevalence of venous and arterial thrombosis, despite thromboprophylaxis, which contributes to morbidity and mortality.

An alternative thromboprophylaxis protocol is in use in Critical Care.

NHS Lothian anti-thrombotic guideline can be obtained on the intranet here.


All patients with proven or suspected COVID pneumonitis should be prescribed weight based thromboprophylaxis unless there is a significant contraindication.

  • Maintain a high level of suspicion and low threshold for investigating/ treating VTE particularly if:
    • Sudden worsening of hypoxaemia, blood pressure or tachycardia
    • Oxygen requirements are disproportionate to severity of pneumonia on CXR
    • Evidence of DVT
  • Every effort should be made to confirm PE/DVT (via CTPA/Doppler US) when at all possible rather than treating empirically with therapeutic anticoagulation.

Check LMWH levels at the required time.

Weight based VTE prophylaxis

Weight <50kg 50-100kg >100-150kg >150kg
eGFR >10 >10 >10 >30
Dalteparin dosing 2500 units daily 5000 units  daily 5000 units  every 12 hours 7500 units  every 12 hours

For the full HIS/SIGN COVID-19 position statement on the prevention and management of thromboembolism in hospitalised patients with COVID-19-related disease please see here.


  • Thrombocytopaenia:  give as normal unless platelets <30x109/L
  • Coagulopathy:  Minor prolongations of PT and APTT (up to 5 seconds) are common in COVID and are not a contraindication to prophylaxis
  • Renal Dysfunction: eGFR 11-30 check LMWH assay at day 10
  • Weight >150kg and eGFR <30 discuss with haematology
  • eGFR <10 or RRT – discuss with renal physicians. If given dalteparin, monitor LMW heparin assay as per NHS Lothian guidance
  • If there is a true contraindication to chemical thromboprophylaxis TED stockings should be used unless contraindicated

Cautions and contraindications to chemical thromboprophylaxis

  • Potential bleeding lesion (e.g. untreated varices, active peptic ulcer in past 3 months)
  • Severe uncontrolled arterial hypertension
  • Uncorrected bleeding disorders (e.g. haemophilias)
  • Active bleeding of any sort
  • Previous history of HIT
  • Platelets <30 or APTTr >1.5 or INR >1.5

Contraindications to TEDS

Contraindications to TEDS

  • Massive leg oedema
  • Pulmonary oedema
  • Severe PVD
  • Major leg deformity
  • Peripheral neuropathy
  • Active dermatitis

 Patients already on anticoagulants in the community

Patients on DOAC pre admission can continue this in hospital provided there are no drug interactions or other contraindications.


Extended Prophylaxis on Discharge

Following treatment for COVID-19 consider the need for extending anticoagulation on discharge. There is no evidence to guide the size of the benefit, the risk of harms, the optimal duration or if any one agent is better than another in this situation. LMWH or a DOAC should be considered on a case by case basis following discussion with haematology or respiratory.