How soon should Deep Vein Thrombosis (DVT) prophylaxis be started in a patient at risk?

DVT Prophylaxis Timing

DVT prophylaxis should be started immediately upon hospital admission for high-risk patients, with pharmacological prophylaxis initiated as soon as possible if there are no contraindications such as active bleeding or recent intracerebral hemorrhage. 1, 2

General Medical and Surgical Patients

For most hospitalized patients at risk for VTE, pharmacological prophylaxis should begin immediately upon admission or recognition of risk factors. 1, 2, 3

• High-risk medical patients (Padua score ≥4 or IMPROVE VTE score ≥2) should receive pharmacological prophylaxis with LMWH, low-dose unfractionated heparin, or fondaparinux throughout their hospitalization 1, 2, 3
• Enoxaparin 40 mg subcutaneously once daily, unfractionated heparin 5000 units subcutaneously twice or three times daily, or fondaparinux 2.5 mg subcutaneously once daily are first-line options 2, 3
• For surgical patients, prophylaxis should be commenced preoperatively and continued for at least 7-10 days postoperatively 1, 4, 5

Stroke Patients: Critical Timing Distinctions

For ischemic stroke patients at high risk (unable to move lower limbs, unable to mobilize independently, previous VTE, dehydration, or cancer), start thigh-high intermittent pneumatic compression (IPC) devices or pharmacological prophylaxis immediately if there is no contraindication. 1

• IPC devices should be applied as soon as possible and within the first 24 hours after admission 1
• Low-molecular-weight heparin should be considered immediately for acute ischemic stroke patients at high risk; use unfractionated heparin for patients with renal failure 1

For intracerebral hemorrhage (ICH) patients, delay pharmacological prophylaxis for at least 48 hours after stroke onset, and only after repeat brain imaging demonstrates hematoma stability. 1

• The earliest safe initiation in ICH studies was 25 hours after admission, with most protocols using 24-48 hours as the threshold 1
• One approach is to start prophylaxis within 24-48 hours after documenting hemorrhage stability on CT imaging 1
• Mechanical prophylaxis with IPC can be started earlier in ICH patients while awaiting the safe window for pharmacological agents 1

Cancer Surgery Patients

Prophylaxis must be started preoperatively and continued for at least 7-10 days, with extended prophylaxis up to 4 weeks postoperatively for major abdominal or pelvic cancer surgery. 1, 2

• Extended prophylaxis with LMWH for up to 4 weeks is specifically recommended for patients undergoing major open or laparoscopic abdominal/pelvic surgery who have high-risk features such as restricted mobility, obesity, or history of VTE 1

Orthopedic Surgery Patients

For hip fracture surgery, fondaparinux should be initiated postoperatively with a mean start time of 6 hours after surgery (range 6±2 hours), but never earlier than 6 hours to avoid major bleeding. 6

• Hip replacement surgery follows similar timing: fondaparinux initiated 6±2 hours postoperatively in 86-92% of patients 6
• Knee replacement surgery uses the same 6±2 hours postoperative initiation window 6
• Extended prophylaxis for hip fracture surgery continues for 21±2 days beyond the initial 7-day perioperative period 6

High Bleeding Risk Patients

For patients with active bleeding or high bleeding risk, use mechanical prophylaxis immediately (IPC devices or graduated compression stockings) until bleeding risk decreases, then reassess for pharmacological prophylaxis. 2, 3, 5

• In lower gastrointestinal bleeding patients, consider delaying pharmacological prophylaxis for 24 hours after ICU admission, as earlier initiation increases transfusion requirements without preventing VTE 7

Critical Pitfalls to Avoid

• Never delay prophylaxis in high-risk ischemic stroke patients beyond 24 hours of admission – the window for IPC application closes at 24 hours, after which venous leg Doppler studies should be considered before starting mechanical prophylaxis 1
• Never start fondaparinux earlier than 6 hours post-surgery – this significantly increases major bleeding risk based on FDA-approved timing 6
• Never use pharmacological prophylaxis within 48 hours of intracerebral hemorrhage without documented hematoma stability on repeat imaging 1
• Never stop extended prophylaxis prematurely in cancer surgery patients – the VTE risk persists for up to 4 weeks postoperatively, and stopping at 7-10 days misses a critical window 1, 2
• Never use anti-embolism stockings alone for post-stroke VTE prophylaxis – they are ineffective as monotherapy 1

Duration Considerations

• Standard prophylaxis continues for 7-10 days for most surgical patients 1, 4, 5
• Extended prophylaxis (up to 4 weeks total) is required for major cancer surgery, hip fracture surgery, and patients with restricted mobility or obesity 1, 2, 6
• For stroke patients remaining immobile longer than 30 days, ongoing pharmacological prophylaxis is recommended beyond the initial period 1, 2