A 30  year  old  man  has  been  admitted  to  hospital  with  severe  multiple  injuries following a motor vehicle accident.

On day 2, his intracranial pressure has stabilised and his head CT shows scattered punctate haemorrhages with subarachnoid blood, with no mass lesion requiring evacuation. His pelvic fracture and right tibia / fibula fracture have been managed with external fixation and a left leg femoral fracture has undergone open reduction and internal fixation.

He has been in good health, but had a DVT 3 years ago and is not on any regular medication.

Outline your approach to prophylaxis for venous thrombo-embolism in this patient.

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College Answer

Risk of VTE is high based on:
•  Major trauma with pelvic and lower limb injury and operative intervention
•  Possibility of a pro-thrombotic disorder

Therapy also has potential risks:
•  Risk of intracranial haematoma expansion with unfractionated or LMW heparin

Management options:
•    Quantify      potential      pro-thrombotic     disorder:      ancillary      history,      previous investigations etc
•  Unilateral mechanical prophylaxis
•  Discuss timing of pharmacological prophylaxis
•  Clinical and imaging surveillance
•  IVC filter

Discussion

One can approach this question systematically:

The risk factors for PE are discussed in a separate chapter, but it is a general outline - not specific to ICU patients. The table of undifferentiated risk factors is reproduced below:

Risk Factors for Pulmonary Embolism

Inherited risk factors

  • Antithrombin III deficiency
  • Protein C deficiency
  • Protein S deficiency
  • Factor V Leiden mutation
  • Hyperhomocysteinaemia

Acute risk factors

  • Surgery
  • Trauma
  • Pregnancy 
  • Burns
  • CVC, Swan-Ganz
  • Spinal injury with paralysis
  • Immobility

Chronic risk factors

  • Smoking
  • Obesity
  • Oral contraception
  • Hormone replacement
  • therapy
  • Malignancy
    Heart failure
  • Lupus anticoagulant
  • Increasing age

Thus, according to these generic risk factors, the patient in the question has several reasons to develop a venous thromboembolism: surgery, trauma, immobility, and a CVC. On top of that, he (a 30 year old man) has already had a DVT at the age of 27, which rings alarm bells. Does he have a weird prothrombotic diathesis? Who knows.

In view of this, he sounds like a candidate for some sort of prophylactic therapy.

If one were to answer this question like an adult, one would produce an answer which resembles the following:

Method of anticoagulation

  • Initially, mechanical thromboprophylaxis only (one leg)
  • Chemical anticoagulation with unfractionated heparin, after a second CT demonstrates no change in the punctate haemorrhages and the SAH.

Rationale for chemical anticoagulation

  • This patient has had surgery, trauma, immobility, and a CVC as risk factors.
  • The likelihood of VTE is high.
  • Chemical anticoagulation improves survival
  • Chemical anticoagulation is more effective than mechanical thromboprophylaxis
  • There is currently a contraindication to adequate mechanical thromboprophylaxis (the leg fracture should not have a calf compressor on it)
  • Unfractionated heparin is inferior to low molecular weight heparin in the context of ICU thromboprophylaxis, but in this case it would be preferred to LMWH because it can be easily reversed with protamine in case of bleeding.

Advantages

  • May improve mortality by decreasing risk of VTE
  • Reversible anticoagulation

Disadvantages

  • The risk of thrombosis may not be reduced
  • The risk of bleeding may increase
  • The presence of existing intracranial haemorrhage (and no mention of an ICP measuring device) means catastrophic intracranial bleeding may result.
  • Vigilant monitoring of clinical and radiological features of increased intracranial pressure may be required
  • Advantages of protection from VTE must be weighed against the risk of intracranial bleeding (it is only day 2 post accident)

Alternatives to chemical anticoagulation

  • An IVC filter is an option, but it is not without its various adverse effects.
  • Purely mechanical thromboprophylaxis is an option, but would be limited to one leg, and would be less effective.

And what if this patient is coagulopathic from his massive transfusion? Should you anticoagulate him, or is he already "auto-anticoagulated"? Well, it turns out, it doesn't matter what you do, these people clot anway. For some reason, coagulopathic surgical patients seem resistant to the effects of thromboprophylaxis.

Realistically speaking, what is this guy's risk of having a major extension of his traumatic subarachnoid bleed? Generally one must say that we really don't know. It is known, however, that haemorrhagic stroke patients who have an unchanged second CT brain don't tend to suffer from any extension of their bleeding. Small scale studies of traumatic brain injuries complicated by haemorrhage also failed to detect any significant increase in the rate of bleed extension due to routine DVT prophylaxis.

References