What is the recommended prophylaxis for patients at risk of deep vein thrombosis (DVT), considering factors such as impaired renal function and high bleeding risk?

DVT Prophylaxis in Hospitalized Patients

For acutely ill hospitalized medical patients at increased risk of thrombosis, use pharmacologic prophylaxis with LMWH (enoxaparin 40 mg subcutaneously once daily), low-dose unfractionated heparin, or fondaparinux throughout hospitalization. 1, 2

Risk Stratification

• Assess all hospitalized patients for VTE risk on admission using validated tools like the Padua Prediction Score (score ≥4 indicates high risk with 11% VTE incidence without prophylaxis) or IMPROVE VTE RAM (score ≥2 indicates increased risk). 3

• High-risk factors include: age >60 years, active malignancy, previous VTE, obesity, restricted mobility, acute medical illness (heart failure, respiratory insufficiency, infection/inflammatory disease), known thrombophilia, recent surgery or trauma, and hormonal therapy. 1, 4, 5

• Low-risk patients (no significant risk factors) should receive early ambulation only - pharmacologic or mechanical prophylaxis is not recommended and increases bleeding risk without benefit. 1, 4

Pharmacologic Prophylaxis for Standard-Risk Patients

First-line options (choose one): 1, 2

• Enoxaparin 40 mg subcutaneously once daily - most commonly used, convenient once-daily dosing 2, 6, 7
• Unfractionated heparin 5000 units subcutaneously every 8 hours (three times daily) - preferred in cancer patients for more consistent anticoagulant effect 2
• Unfractionated heparin 5000 units subcutaneously every 12 hours (twice daily) - acceptable alternative 1
• Dalteparin 5000 IU subcutaneously once daily 2
• Fondaparinux 2.5 mg subcutaneously once daily 1, 2, 5

The choice between agents should be based on local availability, cost, and ease of administration rather than efficacy differences, as all are similarly effective. 1

Special Populations Requiring Dose Adjustments

Renal Impairment (CrCl <30 mL/min)

• Reduce enoxaparin to 30 mg subcutaneously once daily 2, 1
• Alternatively, use unfractionated heparin 5000 units every 8-12 hours (no dose adjustment needed as UFH is not renally cleared) 1
• Fondaparinux 1.5 mg once daily may be used but has limited data in severe renal impairment 5
• LMWH and fondaparinux accumulate in renal impairment, whereas UFH does not - this is a critical consideration 1

Obesity (BMI >30 kg/m²)

• Enoxaparin 40 mg subcutaneously every 12 hours (twice daily) 2
• Alternatively, weight-based dosing at 0.5 mg/kg every 12 hours 2
• Standard prophylactic doses are inadequate in obese patients due to altered pharmacokinetics 2

Cancer Patients

• Unfractionated heparin 5000 units subcutaneously every 8 hours is preferred over twice-daily dosing for more consistent anticoagulation 2, 3
• Cancer patients have particularly high VTE risk and should receive prophylaxis unless contraindicated 1, 3

Critically Ill Patients (ICU)

• Use LMWH or unfractionated heparin with frequent bleeding risk reassessment 1, 3
• Routine ultrasound screening for DVT is not recommended 1

High Bleeding Risk or Active Bleeding

For patients actively bleeding or at high risk for major bleeding, anticoagulant prophylaxis is contraindicated. 1, 2

• Use mechanical prophylaxis instead: 1, 2, 4

  • Intermittent pneumatic compression (IPC) - preferred mechanical method 1, 3
  • Graduated compression stockings (GCS) providing 15-30 mmHg pressure at ankle - alternative option 1, 4, 3

• When bleeding risk decreases and VTE risk persists, substitute pharmacologic for mechanical prophylaxis 1, 2

• Contraindications to pharmacologic prophylaxis include: active bleeding, platelet count <50,000/mcL, recent CNS or spinal bleeding, and high bleeding risk conditions 3

Duration of Prophylaxis

• Continue prophylaxis throughout hospitalization or until the patient is fully ambulatory 2, 4
• Minimum duration of 7-10 days for surgical patients 2
• Do not extend prophylaxis beyond hospital discharge for most medical patients - extended prophylaxis increases bleeding without clear benefit 1, 2, 3
• Selected high-risk patients (multiple VTE risk factors, elevated D-dimer) may benefit from extended prophylaxis, but this requires careful individualization 2

Critical Pitfalls to Avoid

• Neuraxial anesthesia timing: For patients receiving neuraxial anesthesia or spinal puncture, enoxaparin should be withheld for 24 hours before planned manipulation and resumed no earlier than 2 hours following the procedure to prevent spinal hematoma 1

• Surgical timing: For surgical patients, start enoxaparin either 2-4 hours preoperatively or 10-12 hours preoperatively 2

• Heparin-induced thrombocytopenia (HIT) monitoring: Monitor platelet counts every 2-3 days from day 4 to day 14 in patients at risk for HIT 2

• Avoid routine anti-Xa monitoring for prophylactic doses in most patients 2

• Do not use pharmacologic prophylaxis in low-risk patients - this increases bleeding complications without meaningful VTE reduction 1, 4

• Very high-risk surgical patients (e.g., radical cystectomy, radical prostatectomy): Consider combination prophylaxis with both pharmacologic agents and mechanical devices 1