Thromboprophylaxis for Surgical Admissions

Assessment of VTE and bleeding risk

All patients must have their risk of venous thromboembolism (VTE) assessed at admission using the surgical VTE prophylaxis risk assessment proforma (link only active if accessing via NHS network) and then every 72 hours.

Different specialty specific algorithms apply for medical, trauma & orthopaedics and obstetrics (refer to AthenA).

Further information on assessment:

  • For every patient, consider mechanical prophylaxis.
  • Do not offer pharmacological prophylaxis to patients with risk factors for bleeding shown in table 2 below.

Table 1 – Indicators of patients at increased risk of VTE (thrombosis risk factors)

Regard patient as being at increased risk of VTE if they have one or more of the following risk factors:

  • Age >60 years of age
  • Dehydration
  • Obesity (BMI >30kg/m2)
  • Any significant medical illness (e.g. heart, metabolic, endocrine, or respiratory disease; acute infection; inflammatory condition)
  • Use of hormone replacement therapy (HRT)
  • Use of oestrogen-containing contraceptive
  • Active cancer or cancer treatment
  • Known thrombophilia
  • Pregnancy or <6 weeks post-partum
  • Varicose veins with phlebitis
  • Personal history or 1st degree relative with a history of VTE
  • Significantly reduced mobility for 3 days or more
  • Surgery with significant reduction in mobility
  • Critical care admission (e.g. HDU, ICU)
  • Total anaesthetic + surgical time >90 minutes
  • Surgery involving pelvis or lower limb with a total anaesthetic + surgical time >60 minutes
  • Acute surgical admission with inflammatory or intra-abdominal condition

N.B. Consider any admissions or illnesses since pre-operative assessment.

Table 2 – Indicators of patients at high risk of bleeding and contraindication to pharmacological VTE prophylaxis

Regard patient at risk of bleeding, and a contraindication to pharmacological VTE prophylaxis, if they have any of the following risk factors:

  • Active bleeding
  • Recent stroke (within 3 months)
  • Acute gastro-duodenal ulcer
  • Acute bacterial endocarditis - discuss with cardiologist
  • Known hypersensitivity (including heparin induced thrombocytopenia, HIT)
  • Thrombocytopenia (platelets <75 x 109/L)
  • Concurrent use of oral anticoagulant
  • Concurrent use of oral dual anti-platelets - discuss with cardiologist / haematologist
  • Concurrent use of therapeutic heparin
  • Untreated inherited bleeding disorders (e.g. haemophilia, von Willebrand disease)
  • Acquired bleeding disorders, e.g. acute liver failure
  • Uncontrolled hypertension (BP ≥230/120mmHg)
  • Epidural / spinal anaesthesia or lumbar puncture in previous 4 hours or expected within next 12 hours
  • Any other procedure with high bleeding risk
  • Neurosurgery, spinal or eye surgery

N.B. Patients with an Acute Coronary Syndrome or suspected DVT/PE should receive fondaparinux or treatment dose LMWH as appropriate following local clinical guidelines.

General management and treatment options

Elective ward admission

Moderate thrombotic risk† - Enoxaparin SC 40mg on evening before procedure.

High thrombotic risk* - Enoxaparin SC 40mg on evening before procedure. 

Day surgery / same day admissions to general ward

Moderate thrombotic risk† - Mechanical prophylaxis peri-op and Enoxaparin SC 40mg post-op

High thrombotic risk* - Enoxaparin SC 40mg 12 hours pre-op and Enoxaparin SC 40mg 12 hours post-op if haemostasis established OR Mechanical prophylaxis peri-op and Enoxaparin SC 40mg post-op

Emergency admissions

Moderate thrombotic risk† - Enoxaparin SC 40mg at 6pm day of admission.

High thrombotic risk* - Enoxaparin SC 40mg at 6pm day of admission.

†Moderate risk: minor surgery < 30 minutes with ≥ one risk factor or major surgery with no risk factors.

*High risk: major surgery with ≥ one risk factor.

N.B. Adjust enoxaparin dose for weight (<50kg; >100kg) and renal impairment (creatinine clearance (CrCl) <30ml/min) - see here.

Maintenance dose (emergency and elective)

  • Moderate† or high* thrombotic risk - Enoxaparin SC 40mg once daily at 6pm

Continue LMWH until discharge.
Extended prophylaxis can be considered for patients with additional predisposing thrombosis risk factors.

Prophylactic enoxaparin dosing adjustments

Enoxaparin dose is dependent on weight and renal function. Refer to guidance on enoxaparin dose adjustment below in patients with:

  • weight <50kg or >100kg
  • creatinine clearance (CrCl) <30ml/minute.

Precautions with epidural / spinal anaesthesia and lumbar puncture

Do not give LMWH if epidural / spinal anaesthesia or lumbar puncture in previous 4 hours or expected within 12 hours.

Mechanical prophylaxis

Consider mechanical prophylaxis for all patients particularly if they have contraindications to LMWH, or if LMWH not required and early mobilisation is possible.

Apply on admission and continue until there is a return to the pre-morbid level of mobility.

Note, Intermittent Pneumatic Compression (IPC) devices (Flowtron®) or foot impulse devices should be applied peri-operatively.

Advice on how to apply correctly and duration of wear should be given to the patient.

Contraindications to mechanical prophylaxis
Pulmonary oedema Pressure sore
Peripheral arterial / vascular disease Peripheral neuropathy
Cellulitis Local leg conditions, e.g. dermatitis
Leg oedema Extreme deformity
Leg / foot ulceration Acute stroke

General recommendations

  • Facilitate early mobilisation as soon as possible.
  • Ensure adequate hydration.
  • Reassess VTE risk and bleeding risk every 72 hours, or sooner if patient's condition changes. Review treatment plan where appropriate, and document any changes in notes.
  • Document in medical notes if patient is excluded from VTE prophylaxis

 

Guideline reviewed February 2026
Page updated April 2026



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