Compartment Syndrome

Compartment syndrome is without doubt one of the diagnoses that we should never miss. Palpable distal pulses and normal capillary refill times do not exclude compartment syndrome.

Pathophysiology
The pressure inside a body compartment increases. The compartment can't compensate for the increase in pressure, so puts pressure on nerves and blood vessels, making limbs painful and ischaemic. 

Compartment syndrome can affect many regions of the body and is more common in:
- the forearm (volar compartment): humeral shaft fracture, radius and ulna fracture, supracondylar fracture
- leg (the anterior compartment): tibia fracture
It can occur in other regions, including the back, buttocks, thigh, abdomen and foot. Compartment syndrome of the deep posterior compartment of the leg is easily missed.

Compartment syndrome can also occur after soft tissue injuries:
    crush injury
    snake bite
    excessive exertion and exercise - used to be called anterior tibial syndrome. Pain persists despite rest.
    prolonged immobilisation
    constrictive dressings and plaster casts
    soft tissue infection
    seizures
    extravasation of intravenous fluids and medications
    burns
    tourniquets
Patients with a coagulopathy are at particular risk of compartment syndrome.

DiagnosisSuspicion is essential! Suspect if:
 -       one of the fractures listed above is present
 -       one of the soft tissue injuries listed above is present (e.g. crush injury)
 -       patient has a coexistent coagulopathy

Examination - The 6Ps    1. pain - Occurs early, is persistent, tends to be disproportionate compared with the original injury and is not relieved by immobilisation. Passive stretching worsens the pain.
    2. pallor
    3. perishingly cold
    4. pulselessness (a late sign)
    5. paralysis
    6. paraesthesiae - assess by light touch and two-point discrimination, rather than just pinprick, which is less sensitive.
The extremity may be swollen and affected compartments may feel tense and tender on palpation.
  
Pressures:
zero - 10 mmHg = normal tissue pressure
>20mmHg = capillary blood flow may be compromised
>30 - 40mmgHg = muscle and nerve fibers at risk for ischemic necrosis at pressures

Thinking about the Whiteside' Theory:
"the development of a compartment syndrome depends not only on intra-compartment pressure but also depends on systemic blood pressure" treatment may depend on calculating the delta pressure.

Delta pressure = diastolic blood pressure (DBP) — intracompartment pressure
A delta pressure <30 mmHg is suggestive of compartment syndrome

Treatment
This is a surgical / orthopaedic emergency - ischemic injury to muscles and nerves occurs after 4 hours of complete ischemia and becomes irreversible over the next 4 hours, resulting in local rhabdomyolysis and neuropraxis.

Remove all constrictive dressings
Elevation
Traction as appropriate
Analgesia
IV hydration to relieve rhabdomyolysis

References
http://lifeinthefastlane.com/ortho-library/compartment-syndrome/
http://radiopaedia.org/articles/chronic-exertional-compartment-syndrome
http://www.bmj.com/content/325/7364/557?sso=
http://www.trauma.org/archive/resus/DCSacs.html
http://lifeinthefastlane.com/bone-and-joint-bamboozler-002/
http://lifeinthefastlane.com/education/ccc/abdominal-compartment-syndrome/
http://journals.lww.com/anesthesia-analgesia/Fulltext/1996/12000/Acute_Biceps_Compartment_Syndrome_Associated_with.40.aspx
http://bjsm.bmj.com/content/38/2/218.full
http://pedemmorsels.com/compartment-syndrome/
http://calgaryguide.ucalgary.ca/slide.aspx?slide=Acute%20Compartment%20Syndrome.jpg