dvt_proph_pop

DVT, PE, VTE prophylaxis and risk assessment in patients with lower leg immobilization (eg BKPOP plaster for fracture ankle)

Introduction

  • the clinical risk benefit analysis of DVT, PE, VTE prophylaxis in adult patients with a lower limb immobilization due to requirement of a BK POP or similar for a fractured ankle or foot is complicated
  • risk of VTE is higher for patients with ruptured Achille's tendon than with fractures of the ankle, thus this should be taken into account in any risk-benefit analysis 1)
  • we know that immobilization of the lower leg in adults for an extended period is a significant risk factor for DVT but what are the pros and cons of chemoprophylaxis?

Evidence Based Medicine data

  • the recent Cochrane Review by Zee et al in 2017 2) reviewed and collated a meta-analysis of 8 randomized controlled trials (RCTs) that described thrombo-prophylaxis by means of LMWH compared with no prophylaxis or placebo in adult patients with lower-limb immobilization:
    • patients with an immobilized lower leg for an extended period will develop a DVT in approximately 20% of cases of which one tenth will be symptomatic (around 2% of cases) and around 1/3rd of these symptomatic DVTs will present as a clinical PE (around 0.7% of cases), however, fortunately, fatal PE in this group is rare, perhaps in the order of 1 in 4,000 cases (there was only one possible one but not proven PE detected in over 3,600 patients and that patient was over 90yrs of age so likely have to have other potential causes of death)
    • treatment with LMWH resulted in:
      • approximate halving of the rate of all DVTs, symptomatic DVTs, and PEs
      • BUT rate of PEs was still 0.4% (down from 0.7% in untreated group)
      • NO evidence of reduction in PE mortality as none occurred in either group
      • a DOUBLING of adverse outcomes - mainly minor bleeding (8% vs 4% in untreated group)
      • NOTE though that the quality of the data is still rated LOW for all these differences except MODERATE for the halving of all DVT risk
    • this data indicates that fatal PE is extremely rare in this group and it would be currently very difficult to predict which one of the 2000+ patients is likely to die
    • unfortunately, the study is low powered and also does not give us a break down for outcomes for each of the “high risk VTE” factors
  • NICE Clinical Guidelines, No. 92, 2010: 3)
    • “We cannot say definitively that the benefits (of LMWH) outweigh the harms since the mortality rate is too low to make a conclusion about all-cause mortality. The data on pulmonary embolism and major bleeding were very sparse. The only significant outcome was a 50% reduction in all DVT events with LMWH compared with no prophylaxis.”
  • NICE Clinical Guidelines 2018: 4)
    • re-affirmed that there is inadequate evidence to support a clinically significant reduction in mortality or PEs with pharmacological VTE prophylaxis in those with ankle fractures, but there was a reduction in rate of DVTs.
    • “Consider pharmacological VTE prophylaxis with LMWH or fondaparinux sodium for people with lower limb immobilisation whose risk of VTE outweighs their risk of bleeding. Consider stopping prophylaxis if lower limb immobilisation continues beyond 42 days.”

Why don't we offer all patients chemoprophylaxis?

  • some patients are not suitable for chemoprophylaxis as risks are far too high
    • absolute contra-indications to anticoagulation include:
      • acute trauma with risk of haemorrhage
      • coagulopathy including low platelet count less than 50 x 10^9/L or INR > 1.5 or haemophilia
    • relative contra-indications to anticoagulation include:
      • intracranial haemorrhage within last 1 yr
      • severe hypertension
      • recent GIT or genitourinary tract haemorrhage
      • recent intraocular surgery
      • use of anti-platelet agents
      • inherited bleeding disorders
      • acute stroke (which may have caused the fall)
      • falls risk - most of these patients are falls risks and thus at risk of subdural haemorrhages if placed on anticoagulants
    • additional C/I if using LMWH:
      • eGFR < 30mL/min
      • PH sensitivity to any form of heparin (risk of heparin-induced thrombocytopenia)
  • early anticoagulation may compromise the ankle injury
    • potential haemorrhage into and thus increased size of fracture blisters and resultant skin necrosis
    • may delay operative intervention
  • 6 weeks course is expensive and complicated
    • enoxaparin costs $10 per day and requires daily injections, education and patient compliance
    • DOACs / NOACs such as rivaroxaban costs $3-4 a day, is oral but currently off-label for this indication and not covered by PBS
    • need to do clotting profile and FBE, U&E for each patient to ensure they do not have a pre-existing C/I which would further delay discharge from ED
  • risk-benefit of prophylaxis is debatable
    • most DVTs are small distal DVTs with very low risk of resulting in PEs and many of these will undergo spontaneous thrombolysis or clot re-organization, perhaps due to the absence of calf muscle compressions to dislodge any clot that does form
    • patients will still develop DVTs and PEs on chemoprophylaxis just at a lower rate
    • current VTE risk scoring systems do not reliably determine which group would benefit most from prophylaxis
    • no evidence it substantially changes the already very low fatal PE rate and perhaps we would need to treat over 3000 patients to prevent one PE death but at a risk of causing harm to the 3000 patients.
    • the rate of major bleeding on LMWH is around 0.3% while Rx should reduce rate of symptomatic PE's from 0.7% to 0.4% - thus 0.3% will develop bleeding and another 0.3% will be prevented from having a PE.
    • there is a lack of consensus amongst the ED and orthopaedic community on the benefits of prophylaxis while the NSW CEC Stop The Clot campaign's risk assessment algorithm is not validated and is likely to over treat patients 5)

so what should we do?

  • written sensible and targeted patient education
    • reduce risk of DVTs:
      • leg exercises for the unaffected leg
      • toe exercises for the affected leg
      • elevate affected leg and knee exercises
      • ensure adequate hydration
      • cease smoking
    • advise when to seek medical advice such as:
      • new calf or thigh pain
      • chest pain
      • shortness of breath
  • consider chemoprophylaxis in high risk patients who have no significant C/I's
    • “Consider pharmacological VTE prophylaxis with LMWH or fondaparinux sodium for people with lower limb immobilisation whose risk of VTE outweighs their risk of bleeding. Consider stopping prophylaxis if lower limb immobilisation continues beyond 42 days.” 6)
dvt_proph_pop.txt · Last modified: 2019/04/17 02:48 by wh