Synopsis
Select UFH, low-molecular-weight heparin or fondaparinux for treatment and prevention, prescribe a usable weight-based regimen and recognise accumulation, heparin-induced thrombocytopenia and reversal limits.
- LMWH is preferred for most stable VTE treatment because its weight-based effect is predictable and routine APTT monitoring is unnecessary.
- UFH is useful when rapid titration and short offset are needed, in selected severe renal failure, or when thrombolysis, embolectomy or imminent surgery is possible.
- For acute VTE, enoxaparin 1 mg/kg SC every 12 hours is preferred in symptomatic PE, obesity, cancer, recurrent VTE or proximal iliac thrombosis; 1.5 mg/kg once daily is reserved for uncomplicated lower-risk patients.
- Fondaparinux treats DVT or stable PE once daily by weight: 5 mg below 50 kg, 7.5 mg at 50–100 kg and 10 mg above 100 kg, after renal and bleeding assessment.
- Fondaparinux treatment of DVT or PE is contraindicated when creatinine clearance is below 30 mL/min and has no specific antidote; it is not the default for haemodynamically unstable PE.
- UFH treatment commonly starts 80 units/kg IV then 18 units/kg/hour, but use the validated local nomogram and reduce or omit the bolus when bleeding risk is high.
- Protamine rapidly reverses UFH and only partially neutralises LMWH; dose from the actual heparin received and elapsed time, administer slowly, and do not exceed 50 mg in one dose.
- Suspected HIT requires immediate cessation of UFH, LMWH, heparin flushes and heparin-coated devices and initiation of a therapeutic non-heparin anticoagulant when bleeding risk permits.
- Anti-Xa monitoring is selective rather than routine: consider it in severe renal impairment, pregnancy, extremes of weight, unexpected bleeding or thrombosis and prolonged therapeutic exposure.
Key red flags
New thrombosis, skin necrosis, systemic reaction after an IV heparin bolus or a platelet fall of more than 50% typically 5–10 days after exposure suggests immune HIT even if the count remains normal.
Retroperitoneal pain, hypotension, neurological change or a rapid haemoglobin fall during therapeutic heparin requires immediate cessation and major-bleeding assessment.
Acute kidney injury during therapeutic LMWH or fondaparinux can cause accumulation, while an apparently therapeutic dose selected from estimated rather than actual weight can be unsafe.
Investigation priorities
Select dose, establish platelets and haemoglobin and anticipate renal accumulation.
Management branches
DVT or PE is confirmed without haemodynamic instability or immediate procedure.
- Record actual weight, renal function, platelets, bleeding risk, cancer, pregnancy and intended oral-transition pathway.
- Give the indication-appropriate treatment dose, favouring enoxaparin 1 mg/kg twice daily in symptomatic PE or high-recurrence contexts.
- Review renal trajectory, injection technique, platelets and transition or duration before discharge.