Venous thromboembolism in toxicology patients: Prophylaxis and Routine Surveillance

PDF of this guideline is available here

Deep vein thrombosis (DVT) is a serious condition, which can predispose potentially life threatening pulmonary embolism (PE). Venous thromboembolism is thought to be associated with Virchow’s triad of hypercoagulability, stasis and endothelial dysfunction.

Prolonged immobility with hospitalisation can contribute to increased risk for DVT/PE in the unwell medical inpatient. Toxicology patients typically present with short lived intoxication with the average length of stay of approximately 12 hours. It is unusual for this cohort of patients to be immobile for a prolonged period of time.

There has not been much research looking at toxicology patients specifically and their risk for DVT. Patients who are immobile for prolonged periods prior to presentation, such as those who present late following a sedative overdose or those with established rhabdomyolysis, may be at increased risk.

Indication for Thromboprophylaxis

Consistent with PA Hospital guidelines1 for medical inpatients, DVT prophylaxis is indicated in those toxicology patients admitted to the Short Stay Unit or the Ward with:

  • a sedating overdose with prolonged immobility
    • suggested by presentation delayed greater than 12h or CK greater than 1000
  • Active cancer
  • History of DVT/PE
  • Thrombophilia
  • Acute cardiac or respiratory failure
  • Previous MI or CVA
  • History of trauma/surgery in previous month
  • BMI > 30
  • On Oral Contraceptive Pill

Contraindication to Thromboprophylaxis

Thromboprophylaxis is contraindicated if the patient has;

  • Active bleeding
  • Brain/spinal cord lesion
  • Bleeding disorders
  • Platelets < 50 or INR > 1.3
  • Active peptic or duodenal ulcer

Thromboprophylaxis Regime

Chart the patient for:

Patient characteristics Thromboprophylaxis
< 105kg and eGFR > 30 Dalteparin 5000 units s/c daily
< 105kg and eGFR < 30 Unfractionated Heparin 5000 units s/c bd
>105kg regardless of renal function Unfractionated Heparin 5000 units s/c tds

Routine Surveillance for DVT

Patients who take a sedating overdose and have prolonged immobility, suggested either historically with a presentation delayed more than 12 hours post ingestion or clinically with established rhabdomyolysis (evidenced by a CK > 1000), should have routine duplex of bilateral lower limbs performed. If a DVT is present, consultation with the vascular medicine team regarding anticoagulation therapy and duration is advised. If DVT is absent, immobile patients should still receive DVT prophylaxis.


  1. Director Vascular Medicine and VTE Prevention CNC, 2014. Venous Thromboembolism Prophylaxis Guidelines Procedure No. 01506/v8/05/2014. Princess Alexandra Hospital local protocol approved by the Executive Director Medical Services. Available from URL: