Thromboprophylaxis

Principles

Vena Cava Filter

Physical sieve placed in the IVC to catch emboli from the deep veins prior to a potentially fatal pulmonary embolism. IVC filters:

  • Are placed endovascularly via the femoral or RIJ veins
  • Are indicated in patients:
    • At high of VTE with an absolute contraindication to chemoprophylaxis
    • Unable to achieve therapeutic anticoagulation with a known DVT/PE
    • With ongoing PE despite full anticoagulation for DVT
  • Have no evidence for mortality reduction
  • May ↓ symptomatic PE
  • ↑ Risk of DVT
    • Result in venous stasis of lower limbs
    • May result in IVC occlusion with significant thrombus burden
  • Should be retrieved when no longer required
    • Retrievable designs should be used
    • A system for follow-up of patients and removal should exist

Practice

Approach:

  • Pharmacological
    • All patients should receive chemoprophylaxis unless there is a particular contraindication:
      • Active haemorrhage
      • Thrombocytopenia
        • Generally ⩽50
        • ⩽100 in some cases
          Cardiothoracic, neurosurgery.
      • Planned procedure requiring thromboprophylaxis interruption
    • GFR >30mL/min
      Use enoxaparin:
      • ⩽50kg: 20mg SC daily
      • 50-120kg: 40mg SC daily
      • >120kg: 0.25mg/kg SC Q12H
    • GFR <30mL/min
      Heparin:
      • ⩽120kg: 5000 IU SC BD
      • >120kg: 5000 IU SC TDS
  • Mechanical
    • Intermittent pneumatic calf compression
      May reduce incidence by up to 60% in operative patients.
      • Treatment of choice where bleeding risk is high
    • IVC filter
      Reasonable to use in patients with:
      • High VTE risk and contraindications to anticoagulation
      • Recurrent PE despite therapeutic anticoagulation

Marginal and Ineffective Therapies

  • Compression stockings
    • Do not ↓ DVT risk
    • ↑ Falls (slippery!) risk
    • ↑ Pressure areas
    • Create a lot of waste

Key Studies

IVC Filters:

  • Ho et al. (2019)
    • 240 non-pregnant Australian trauma patients with ISS >15 and a contraindication to chemoprophylaxis, without confirmed PE or systemic anticoagulation
    • Block randomised multicentre (4) trial
    • 80% power for 8.5% ↓ in symptomatic PE, for control group PE rate of 9%
      This is a 94% RRR, which is ambitious.
    • IVC filter vs. standard care
      • IVC filter
        • 89% within 24 hours
        • Removed once chemoprophylaxis established
        • Filter type at radiology discretion
      • Standard care
        • IVC filter permitted if well established indication
    • IPCC to uninjured legs
    • Routine DVT ultrasound
    • No significant difference in symptomatic PE or death (13.9% vs 14.4%)
    • Secondary outcomes:
      • Significant ↓ (0% vs 14.7%) in symptomatic PE in patients who did start chemoprophylaxis within 7 days of injury
    • Single centre provided almost all patients

Other:

  • PREVENT (2019)
    • 2,000 ICU patients with no contraindication to chemoprophylaxis
    • International, multi-centre RCT
    • 80% power to detect 3% absolute ↓ in proximal DVT, assuming 7% control group incidence
      • Intermittent pneumatic compressors. vs standard care
        • IPCC
          • Sequential compression used for >18 hours/day
        • Standard care
          • IPCC used only if chemoprophylaxis was interrupted
    • No change in proximal DVT (3.9% vs 4.2%)
    • No change in PE, DVT/PE, or mortality
    • IPCC offer no additional benefit over chemoprophylaxis alone

References

  1. Ho KM, Rao S, Honeybul S, et al. A Multicenter Trial of Vena Cava Filters in Severely Injured Patients. New England Journal of Medicine. 2019;381(4):328-337. doi:10.1056/NEJMoa1806515
  2. Arabi YM, Al-Hameed F, Burns KEA, et al. Adjunctive Intermittent Pneumatic Compression for Venous Thromboprophylaxis. New England Journal of Medicine. 2019;380(14):1305-1315. doi:10.1056/NEJMoa1816150