VTE prophylaxis.
Risk-assess every admission (Padua, IMPROVE-BLEED, Caprini), pick the agent, adjust for renal function and body size, and switch to mechanical when you can't anticoagulate. Plus orthopedics, cancer, pregnancy, and HIT — and the CrCl check everyone misses.
Reviewed June 2026 · verify against current guidelines
Start With Risk
Assess, Start, Hold
Who needs prophylaxis
| Medical high risk | Padua ≥4 or Geneva ≥3. |
|---|---|
| Surgical | Caprini score guides intensity. |
| Low risk | Early ambulation; no drug needed. |
| High bleeding risk | IMPROVE-BLEED ≥7. Use mechanical, not drug. |
Start, hold, restart
| Start | On admission if high VTE risk and acceptable bleeding risk. |
|---|---|
| Hold | Active bleed, platelets <50k, before surgery or neuraxial procedures. |
| Restart | Once hemostasis is secure after the procedure. |
Reassess risk daily. Follow local protocols for hold and restart timing.
VTE venous thromboembolism
Pick the Agent
Choose Your Anticoagulant
For medical inpatients ASH 2018 suggests LMWH or fondaparinux over UFH, and over DOACs. DOACs still have a role: rivaroxaban is FDA-approved for select medical patients, and DOACs are an equal first-line alternative to LMWH after joint replacement.
Standard prophylactic dosing
| Agent | Dose / role |
|---|---|
| Enoxaparin (LMWH) | 40 mg SC daily. First-line; reduce to 30 mg if CrCl <30. |
| UFH | 5000-7500 units SC q8-12h. Preferred if CrCl <30. |
| Fondaparinux | 2.5 mg SC daily. Use in HIT history. Avoid CrCl <30. |
| DOAC | Rivaroxaban 10 mg daily (select medical or ortho). Apixaban 2.5 mg BID (ortho). |
UFH does not accumulate in renal failure, so it is the safer parenteral choice when CrCl is under 30.
LMWH low-molecular-weight heparinUFH unfractionated heparinHIT heparin-induced thrombocytopeniaDOAC direct oral anticoagulant
Adjust the Dose
Renal and Body Size
When standard dosing is wrong
| CrCl <30 | Enoxaparin 30 mg SC daily, or use UFH 5000 q8-12h. |
|---|---|
| Obesity (BMI ≥40) | Higher dose: enoxaparin 40 mg BID or UFH 7500 units q8h. |
| Monitoring | Routine anti-Xa not needed. Consider in extremes. |
Check CrCl and weight before ordering. The reflex 40 mg enoxaparin is wrong in severe renal failure.
CrCl creatinine clearanceBID twice daily
Can't Anticoagulate
Mechanical Prophylaxis
When bleeding risk is too high
- IPC is the preferred mechanical method. Use when bleeding risk is unacceptable.
- Graduated stockings alone do not work and may harm (CLOTS-1).
- Combine IPC with drug prophylaxis for highest-risk surgery.
- Reassess daily. Add the drug once bleeding risk clears.
IPC contraindications
| Absolute | Severe PAD or limb ischemia (ABPI <0.5). Acute DVT in that leg. |
|---|---|
| Relative | Leg wounds, grafts, dermatitis, fracture, cellulitis, massive edema, neuropathy. |
Mechanical is a bridge, not a substitute. Switch to the drug when safe.
IPC intermittent pneumatic compressionPAD peripheral arterial diseaseABPI ankle-brachial pressure index
Special Populations
Surgery, Cancer, Pregnancy
Tailor the plan
| Joint replacement | LMWH or DOAC over aspirin (CRISTAL). DOACs OK here. |
|---|---|
| Hip fracture | LMWH preferred. Avoid DOACs (insufficient evidence). |
| Cancer inpatient | Pharmacologic px if active cancer plus acute illness. |
| Cancer ambulatory | High-risk (Khorana ≥2): consider apixaban or rivaroxaban. |
| Pregnancy | LMWH. DOACs and warfarin are contraindicated. |
| HIT (history/active) | Avoid all heparin. Use fondaparinux or non-heparin agent. |
Extend prophylaxis past discharge after major joint surgery: 35 days for hip, 14 days for knee.
px prophylaxisHIT heparin-induced thrombocytopenia
Don't Get Burned
Where Interns Slip
High-risk errors
- Adding prophylaxis to a patient already on therapeutic anticoagulation. They are already covered; do not stack.
- Ordering enoxaparin without checking CrCl. If under 30, use 30 mg daily or UFH.
- Skipping mechanical prophylaxis when the drug is held.
- Leaving prophylaxis held after a procedure. Restart when safe.
- Using stockings instead of IPC. Stockings fail alone.
- Continuing heparin as platelets fall. Think HIT.
Check platelets and CrCl before every prophylaxis order. Reassess the plan on every day's note.
HIT heparin-induced thrombocytopenia
Sources
Verify against current guidelines and local protocol before acting.
- Schunemann HJ et al. ASH 2018 guidelines: prophylaxis for hospitalized and nonhospitalized medical patients. Blood Adv 2018;2(22):3198.
- Anderson DR et al. ASH 2019 guidelines: prevention of VTE in surgical hospitalized patients. Blood Adv 2019;3(23):3898.
- Nendaz M et al. Multicentre validation of the Geneva Risk Score (ESTIMATE). Thromb Haemost 2014;111:531. High risk ≥3.
- Cuker A et al. ASH 2018 guidelines: heparin-induced thrombocytopenia. Blood Adv 2018;2(22):3360.
- Sidhu VS et al. Aspirin vs enoxaparin for VTE prophylaxis after hip or knee arthroplasty (CRISTAL). JAMA 2022;328(8):719.
- Dennis M et al. Intermittent pneumatic compression after stroke (CLOTS-3). Lancet 2013;382(9891):516.
- Dennis M et al. Thigh-length graduated compression stockings after stroke (CLOTS-1). Lancet 2009;373(9679):1958.
- Key NS et al. VTE prophylaxis and treatment in patients with cancer: ASCO guideline update. J Clin Oncol 2023;41(16):3063.
- UpToDate. Prevention of VTE in acutely ill hospitalized medical adults (2026); enoxaparin renal and obesity dosing per FDA prescribing information.
- UpToDate. Prevention of VTE in adults undergoing hip fracture repair or hip/knee replacement (2026). Agent choice and duration.
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