Venous thromboembolism prophylaxis

Red Flags

Active bleeding or recent intracranial haemorrhage — pharmacological prophylaxis contraindicated; use mechanical (intermittent pneumatic compression, GCS) until bleeding controlled^[1]
Heparin-induced thrombocytopenia (HIT) — stop heparin; alternative anticoagulation (argatroban, fondaparinux); haematology consult; do not start LMWH^[1]
Severe renal impairment (eGFR <30) — adjust LMWH dose, consider unfractionated heparin or graduated compression stockings; DOACs limited or avoided^[1]
Pregnancy with VTE risk factors — antenatal LMWH 6 weeks postpartum; assess at booking, after admission, and at 28 weeks^[1]

First-line treatment

Interventions

Universal risk and bleeding assessment^[1]
All hospitalised adults assessed within 24 h of admission and after major change in clinical status; document risk and prophylaxis prescribed; integrate into electronic admission bundle
Pharmacological prophylaxis for moderate-high VTE risk^[1]
LMWH preferred over UFH; fondaparinux alternative; do NOT use DOAC for in-hospital prophylaxis (ASH 2018); duration: until ambulant or per pathway (orthopaedic 14–35 days, cancer surgery up to 4 weeks, medical typically until discharge)
Mechanical prophylaxis when pharmacological contraindicated^[1]
Intermittent pneumatic compression preferred over graduated compression stockings; combine with pharmacological in highest-risk surgical (orthopaedic, cancer); discontinue when ambulant
Outpatient VTE prevention^[1]
Long-distance travel >6–8 h: ambulation, hydration; GCS or LMWH only for high-risk individuals (prior VTE, active cancer, recent surgery, advanced pregnancy). Routine prophylaxis NOT recommended for long-term care, outpatients, or minor risk factors
Intermittent pneumatic compression (IPC)^[1]
Preferred mechanical option over graduated compression stockings; sequential calf or thigh-length devices; compliance is critical — re-apply after toilet, mobilisation; combine with pharmacological in highest-risk

First-line drug therapy

Drug	Class	Adult	Paediatric	Notes
Enoxaparin (LMWH)^[1]	Low-molecular-weight heparin	40 mg SC daily; 30 mg BD in some surgical regimens; 20 mg daily if eGFR <30 (or use UFH)	0.5 mg/kg/dose BD	First-line pharmacological prophylaxis; weight-adjusted for BMI ≥40 (enoxaparin 0.5 mg/kg BD); HIT incidence ~1%; renal dose adjustment
Dalteparin (LMWH alternative)^[1]	Low-molecular-weight heparin	5000 units SC daily for prophylaxis	—	Alternative to enoxaparin; preferred for cancer-associated VTE (CLOT trial)
Unfractionated heparin (UFH)^[1]	Unfractionated heparin	5000 units SC every 8 or 12 h	—	Preferred when eGFR <30, dialysis, or rapid reversal needed; higher HIT risk than LMWH; no monitoring needed for prophylactic dose
Fondaparinux^[1]	Synthetic factor Xa inhibitor	2.5 mg SC daily	—	Alternative when LMWH contraindicated (HIT, religious dietary preferences avoiding porcine); no antidote available; renal dose adjustment
Apixaban or rivaroxaban (post-arthroplasty extended)^[1]	DOAC (factor Xa inhibitor)	Apixaban 2.5 mg PO BD × 12 days (knee) or 35 days (hip); rivaroxaban 10 mg PO daily × 14 days (knee) or 35 days (hip)	—	Approved for post-orthopaedic prophylaxis; not for acute medical inpatient prophylaxis (ASH 2018); MAGELLAN suggested signal for medical prophylaxis but ASH does not endorse

Enoxaparin (LMWH)^[1]

Low-molecular-weight heparin

Adult: 40 mg SC daily; 30 mg BD in some surgical regimens; 20 mg daily if eGFR <30 (or use UFH)
Paediatric: 0.5 mg/kg/dose BD

First-line pharmacological prophylaxis; weight-adjusted for BMI ≥40 (enoxaparin 0.5 mg/kg BD); HIT incidence ~1%; renal dose adjustment

Dalteparin (LMWH alternative)^[1]

Low-molecular-weight heparin

Adult: 5000 units SC daily for prophylaxis
Paediatric: —

Alternative to enoxaparin; preferred for cancer-associated VTE (CLOT trial)

Unfractionated heparin (UFH)^[1]

Unfractionated heparin

Adult: 5000 units SC every 8 or 12 h
Paediatric: —

Preferred when eGFR <30, dialysis, or rapid reversal needed; higher HIT risk than LMWH; no monitoring needed for prophylactic dose

Fondaparinux^[1]

Synthetic factor Xa inhibitor

Adult: 2.5 mg SC daily
Paediatric: —

Alternative when LMWH contraindicated (HIT, religious dietary preferences avoiding porcine); no antidote available; renal dose adjustment

Apixaban or rivaroxaban (post-arthroplasty extended)^[1]

DOAC (factor Xa inhibitor)

Adult: Apixaban 2.5 mg PO BD × 12 days (knee) or 35 days (hip); rivaroxaban 10 mg PO daily × 14 days (knee) or 35 days (hip)
Paediatric: —

Approved for post-orthopaedic prophylaxis; not for acute medical inpatient prophylaxis (ASH 2018); MAGELLAN suggested signal for medical prophylaxis but ASH does not endorse

Safety-net

Take prescribed prophylactic injections daily — most VTE happens after discharge in some surgical groups; complete the prescribed duration^[1]
Calf swelling, pain, sudden breathlessness, chest pain, or haemoptysis after recent admission or surgery — emergency department for VTE assessment^[1]
Resume normal activity and walking as early as possible after admission or surgery — early mobilisation reduces VTE risk most effectively^[1]

Referral criteria

Suspected DVT (calf swelling, pain) or PE (sudden breathlessness, chest pain, haemoptysis)Emergency department / acute medical assessment with D-dimer and imaging^[1]
HIT suspicion (platelet drop ≥50% or new thrombosis on heparin)Haematology and switch to alternative anticoagulant^[1]
Pregnancy with personal or family VTE history requiring antenatal prophylaxisJoint obstetric and haematology^[1]
Recurrent unprovoked VTE or significant anticoagulation contraindicationsHaematology / thrombosis specialist^[1]

Clinical summary

VTE risk-based pharmacological and mechanical prophylaxis for hospitalised medical, surgical, and obstetric patients, and high-risk outpatients.

References

1.ASH 2018 Guidelines for the Management of VTE — Prophylaxis for Hospitalised and Non-Hospitalised Medical Patients (with 2024 ACCP/CHEST refresh); NICE NG89; CHEST Antithrombotic Therapy (2024)