It is defined as a critical pressure increase within a confined compartmental space, causing a decline in the perfusion pressure to the compartment tissue; without timely diagnosis and treatment, it will lead to ischaemia, necrosis, and permanent disability of the affected region.
Compartment syndrome comes in two forms: acute and chronic. This article only covers the recognition and management of the acute form, which is a surgical emergency. If left undiagnosed and treated, it can lead to limb loss, multi-organ failure, and death.
Where there is a closed (fascial) compartment, any fluid that is deposited within the compartment will cause an increase in the intracompartmental pressure. As this pressure increases, the lower pressure venous system will first be compromised, leading to venous congestion and a further increase in the intracompartmental pressure.
The capillaries will be compressed and eventually the arterial supply to the muscles will cease, leading to ischaemia and subsequent infarction. In the final stages, the arteries will be compressed*.
*The condition should however be recognised and treated well before this point.
The leg is most commonly affected by compartment syndrome, with the four fascial compartments present (anterior tibial, lateral, and superficial & deep posterior compartments). The forearm, gluteal region, and rarely the abdominal cavity can also be affected.
There are many causes of compartment syndrome, but the common causes in the limbs are :
- Following traumatic injury, such as long bone fractures, vascular injuries, crush injuries, or long lies
- Tight casts or splints
- Deep vein thrombosis (DVT)
- Cannulation or arterial puncture in anticoagulated patients
- Post-ischaemic swelling or post-operatively
- This may represent an iatrogenic reperfusion injury after any vascular reconstruction
The ‘6 P’s’ are a commonly used set of symptoms that represent arterial insufficiency. Remember that most cases of compartment syndrome are recognised much earlier than this stage, as the ‘6 P’s’ are features of end stage compartment syndrome (and therefore a ‘dead’ limb).
The clinical present should be aiming to recognise the earlier features of compartment syndrome. The core symptoms (with the pulses present) are:
- Pain or tenderness – disproportionate to the injury or is worsening despite treatment (ischaemia) or worse on passive movement (typically assessed by moving a digit in the hand or foot). This may present as a patient with increasing analgesia requirements.
- Paraesthesia – in the cutaneous distribution of the affected nerve (nerve compression).
- Swelling – Any compartment affected will feel tense and bulging, feeling ‘wood-like’ when compared to the contralateral limb
Often, patients at risk of compartment syndrome are sedated on critical care. This makes assessing pain and tenderness much more difficult and you may have to rely on the physical signs such as a relative tachycardia, or swollen/tight compartments.
In end-stage disease, the features are of acute arterial insufficiency (the ‘6 P’s’), yet at this stage, the limb is not salvageable:
- Pain disproportionate to the injury
- Pallor (or mottled, which becomes non-blanching)
- Perishingly cold
The diagnosis of compartment syndrome is essentially clinical, based on the symptoms and risk factors present. A very high degree of clinical suspicion is therefore needed for compartment syndrome in post-operative and trauma patients.
Compartmental pressure can be measured by invasive compartment pressure monitors. This calculates a deltaP value (diastolic blood pressure minus the intracompartmental pressure), the threshold deltaP value often used for performing a fasciotomy is <30mmHg. However, less than half of all UK orthopaedic consultants use any form of compartment pressure monitoring.
One should treat the patient and not the numbers; if there is any doubt about the diagnosis, seek urgent help and advice. There is absolutely no role for imaging or additional bloods tests. Whilst an arterial blood gas may be useful, it should not delay treatment.
The most important part of the management is early recognition and urgent discussion with the orthopaedic/general/vascular/plastic surgeon.
Initial management steps include:
- Keep the limb at a neutral level with the patient (do not elevate or lower).
- Improve oxygen delivery with high flow oxygen and augment blood pressure with IV crystalloids.
- Remove any constricting dressings or split any circumferential casts.
- Treat symptomatically with opioid analgesia (with anti-emetics).
The definitive treatment is with an emergency all-compartment fasciotomy to relieve the pressure inside the compartment. The skin incisions are left open, and a re-look is planned for 24-48 hours.
One should watch out for the consequences of rhabdomyolysis or reperfusion injury in patients with evidence of muscle necrosis, crush injuries and long lies, monitoring electrolytes and renal function closely. Ensure adequate hydration with early involvement of critical care and the renal physicians if suspected.