DVT prophylaxis

Risk Stratification - The Clot Setup

Central to DVT prevention is quantifying patient risk. The Caprini score is a common tool for this, stratifying patients to guide prophylaxis intensity.

• 📌 Virchow's Triad (SHE):
  • Stasis: Immobility (>3 days), surgery >30 min, obesity (BMI >30), paralysis.
  • Hypercoagulability: Malignancy, sepsis, OCPs/HRT, pregnancy, inherited thrombophilia (e.g., Factor V Leiden).
  • Endothelial Injury: Major surgery (esp. orthopedic, pelvic, cancer), trauma, central venous catheters.

⭐ Orthopedic surgery (especially total hip or knee arthroplasty) carries one of the highest risks for VTE, often mandating aggressive prophylaxis.

Pharmacologic Prophylaxis - Better Living Through Chemistry

• Low Molecular Weight Heparin (LMWH): First-line for most patients.
  • Examples: Enoxaparin (40 mg SC daily), Dalteparin.
  • Mechanism: Potentiates antithrombin III, primarily inhibiting Factor Xa.
  • Pros: Predictable dosing, no routine monitoring needed.
• Unfractionated Heparin (UFH):
  • Dosing: 5000 units SC every 8-12 hours.
  • Mechanism: Potentiates antithrombin III, inhibiting both Factor Xa and Thrombin (IIa).
  • Niche: Preferred in severe renal dysfunction (CrCl < 30 mL/min) and when rapid reversal may be needed.
• Fondaparinux:
  • Mechanism: Synthetic pentasaccharide, pure Factor Xa inhibitor.
  • Use: Key alternative for patients with a history of Heparin-Induced Thrombocytopenia (HIT).

⭐ High-Yield: LMWH is renally cleared. In patients with severe chronic kidney disease (CKD), UFH is the safer choice due to its hepatic metabolism and shorter half-life, reducing the risk of accumulation and bleeding.

Mechanical & Combined Therapy - Squeeze and Synergize

• Mechanical Prophylaxis: Utilized when anticoagulants are contraindicated (e.g., high bleeding risk) or in addition to them.
  • Intermittent Pneumatic Compression (IPC): Inflatable sleeves on legs/feet that cyclically inflate and deflate, enhancing blood flow and stimulating fibrinolysis. Mimics muscle contraction.
  • Graduated Compression Stockings (GCS): Provide a pressure gradient (highest at the ankle, decreasing proximally) to reduce venous stasis.
  • Venous Foot Pumps (VFP): Inflate a bladder under the foot, compressing the plantar venous plexus.

• Combined Therapy: For highest-risk patients (e.g., major orthopedic surgery, trauma, high VTE scores), mechanical methods are often combined with pharmacologic prophylaxis for synergistic effect.

⭐ High-Yield: In patients with active bleeding or at extremely high risk for bleeding (e.g., hemorrhagic stroke, recent major surgery), mechanical prophylaxis with IPCs is the primary method for VTE prevention.

Contraindications & Special Cases - Navigating Nuances

• Absolute Contraindications: Active bleeding, recent intracranial/ocular surgery, severe thrombocytopenia (< 20,000/μL), or known bleeding diathesis.

• Relative Contraindications: High-risk procedures (neurosurgery), recent major trauma, platelet count < 50,000/μL, or uncontrolled hypertension.

• Special Populations:

  • Neurosurgery/Spinal Trauma: Primarily mechanical prophylaxis (SCDs) to prevent epidural hematoma.
  • Renal Insufficiency (CrCl < 30 mL/min): Use unfractionated heparin (UFH); avoid LMWH and most DOACs.
  • Heparin-Induced Thrombocytopenia (HIT): Stop all heparin. Use direct thrombin inhibitors (e.g., argatroban).

⭐ In patients with severe renal failure (Creatinine Clearance < 30 mL/min), unfractionated heparin is the preferred anticoagulant for DVT prophylaxis because LMWH is cleared by the kidneys and can accumulate, increasing bleeding risk.

High‑Yield Points - ⚡ Biggest Takeaways

• Virchow's triad (stasis, hypercoagulability, endothelial injury) is the fundamental cause of postoperative DVT.
• Early and frequent ambulation is key for all patients, especially those at low risk.
• Use risk scores like Caprini to determine the appropriate level of prophylaxis.
• Mechanical prophylaxis (e.g., IPC devices) is vital when there's a high bleeding risk.
• LMWH (enoxaparin) or low-dose unfractionated heparin are first-line pharmacologic agents for moderate-to-high risk.
• Highest risk includes major orthopedic (hip/knee) and cancer surgeries.