DVT Prophylaxis in Hospitalized Adults
All hospitalized adult medical patients with acute illness or reduced mobility should receive pharmacologic thromboprophylaxis with LMWH, unfractionated heparin (UFH), or fondaparinux unless bleeding or other contraindications exist, with LMWH preferred over UFH. 1, 2
Risk Stratification and Agent Selection
Acutely Ill Medical Patients (Non-ICU)
For general medical inpatients, the evidence strongly supports routine pharmacologic prophylaxis:
- First-line agents (all Grade 1A): 3
- Enoxaparin 40 mg subcutaneous once daily (preferred)
- Dalteparin 5,000 units subcutaneous once daily
- UFH 5,000 units subcutaneous every 8 hours
- Fondaparinux 2.5 mg subcutaneous once daily
LMWH is strongly preferred over UFH due to once-daily dosing, lower risk of heparin-induced thrombocytopenia, and superior efficacy. 1, 4 The 2017 Surviving Sepsis guidelines specifically recommend LMWH over UFH for VTE prophylaxis (strong recommendation, moderate quality evidence). 1
Critically Ill/ICU Patients
All ICU patients require risk assessment on admission with most receiving thromboprophylaxis (Grade 1A). 3 Use the same agents as medical patients, with LMWH or UFH preferred. 1
Surgical Patients
All patients undergoing major surgery (>30 minutes) require prophylaxis starting preoperatively:
- Standard dosing: 5, 3
- Enoxaparin 40 mg 10-12 hours preoperatively, then once daily
- Dalteparin 5,000 units 10-12 hours preoperatively, then once daily
- UFH 5,000 units every 8 hours starting 2-4 hours preoperatively
- Fondaparinux 2.5 mg starting 6-8 hours postoperatively
Duration: Minimum 7-10 days for all surgical patients. 5, 6
Extended prophylaxis (up to 4 weeks) is strongly recommended for major abdominal/pelvic cancer surgery, hip arthroplasty, and hip fracture surgery (Grade 1A). 5, 6, 3 This reduces VTE rates from 12-16% to 5-7%. 6
Contraindications and Special Situations
When Pharmacologic Prophylaxis is Contraindicated
Use mechanical prophylaxis (intermittent pneumatic compression devices preferred over graduated compression stockings alone) when: 3
- Active bleeding
- Severe thrombocytopenia (platelets <50,000/μL)
- High bleeding risk procedures (neurosurgery, intracranial hemorrhage)
Mechanical prophylaxis alone reduces DVT by 66% but only modestly reduces PE by 31%, making it inferior to pharmacologic methods. 6 Therefore, start pharmacologic prophylaxis as soon as bleeding risk resolves—typically 24-72 hours post-neurosurgery. 7
Renal Impairment
For creatinine clearance <30 mL/min: 5, 8
- Enoxaparin 30 mg once daily (reduced dose)
- UFH 5,000 units every 8-12 hours (no dose adjustment needed)
- Avoid dalteparin, tinzaparin, and fondaparinux
Obesity
For patients >150 kg, consider enoxaparin 40 mg every 12 hours instead of once daily. 8
Cancer Patients
Hospitalized cancer patients with acute illness require prophylaxis (Grade 1A). 9, 5 Use standard LMWH dosing. Cancer doubles the baseline VTE risk, and 40% of hospitalized cancer patients meet high-risk criteria. 10
Do NOT use routine prophylaxis for:
- Outpatient chemotherapy infusions
- Minor procedures
- Stem cell/bone marrow transplantation 9
Exception: Multiple myeloma patients on thalidomide/lenalidomide-based regimens require aspirin (low-risk) or LMWH (high-risk). 9
Duration of Prophylaxis
Continue prophylaxis for the entire hospitalization or until fully ambulatory. 5, 3
Do NOT extend prophylaxis after hospital discharge for general medical patients (strong recommendation). 2 The exception is post-surgical patients in high-risk categories who should receive extended prophylaxis as noted above.
Critical Pitfalls to Avoid
Never use aspirin alone for VTE prophylaxis—it is ineffective (Grade 1A). 3
Do not use direct oral anticoagulants (DOACs) for in-hospital prophylaxis—they are not approved for this indication and drug interactions with other hospital medications are problematic. 11, 2
Avoid mechanical prophylaxis as monotherapy unless pharmacologic methods are absolutely contraindicated—it is significantly less effective. 6, 3
Do not delay prophylaxis—start on admission after bleeding risk assessment. The majority of hospital-acquired VTE events are preventable with appropriate prophylaxis. 3
For neuraxial anesthesia/epidural catheters: Hold LMWH 10-12 hours before procedure and restart no sooner than 2 hours after catheter removal to avoid spinal hematoma. 5
Monitor for heparin-induced thrombocytopenia in patients receiving UFH >5 days—LMWH has lower risk but is not zero.