DVT prophylaxis

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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.

Anticoagulant Mechanisms: UFH, LMWH, and Fondaparinux

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.

DVT Prophylaxis Pump Types and Therapy

  • 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.

Practice Questions: DVT prophylaxis

Test your understanding with these related questions

A 26-year-old man presents with a 2-day history of worsening right lower leg pain. He states that he believes his right leg is swollen when compared to his left leg. Past medical history is significant for generalized anxiety disorder, managed effectively with psychotherapy. He smokes a pack of cigarettes daily but denies alcohol and illicit drug use. His father died of a pulmonary embolism at the age of 43. His vital signs include: temperature 36.7°C (98.0°F), blood pressure 126/74 mm Hg, heart rate 74/min, respiratory rate 14/min. On physical examination, the right lower leg is warmer than the left, and dorsiflexion of the right foot produces pain. Which of the following conditions is most likely responsible for this patient’s presentation?

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Flashcards: DVT prophylaxis

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What surgical procedure is associated with fat embolus? _____

TAP TO REVEAL ANSWER

What surgical procedure is associated with fat embolus? _____

Liposuction

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