Write a short note on Compartment Syndrome.

The Mechanism

Compartment syndrome is a surgical emergency in which the pressure within a closed fascial compartment rises high enough to cut off the perfusion of the tissues inside it. Muscles and nerves are enclosed by tough, inelastic fascia, so when their volume increases (swelling, bleeding) or the compartment is externally constricted, the pressure has nowhere to go. As the pressure rises it first exceeds the low pressure in the veins (impairing venous drainage, which raises the pressure further in a vicious cycle) and then obstructs capillary flow, causing ischaemia that, if unrelieved, leads to irreversible muscle and nerve necrosis within hours.

Causes & the '6 PS'

Common causes are fractures, crush injuries, reperfusion after vascular injury, a tight plaster cast or dressing, and burns. The clinical features are the '6 Ps', but their timing is the crucial teaching point:

• Pain — the earliest and most important sign: severe, out of proportion to the injury, and classically worsened by passive stretching of the muscles in the compartment.
• Paraesthesia (early nerve ischaemia).
• Pallor, Paralysis, Pulselessness and Perishing cold — these are late signs.

Diagnosis & Management

The diagnosis is primarily clinical, supported where needed by measuring the compartment pressure. Management is an emergency: remove any constricting cast or dressing, and perform an urgent fasciotomy — surgically opening the fascia to release the pressure and restore perfusion — before ischaemic necrosis becomes established.

The Pathophysiology & Volkmann's Contracture

The damage is an ischaemia–reperfusion process: rising pressure halts capillary perfusion, muscle becomes ischaemic, and swelling worsens the pressure in a self-amplifying loop. If muscle is allowed to die and then fibrose, the limb is left with a fixed deformity — the classic Volkmann's ischaemic contracture of the forearm being the historical example. Dead muscle also releases myoglobin and potassium, so an unrelieved or reperfused compartment can cause rhabdomyolysis, acute kidney injury and hyperkalaemia — the 'crush syndrome'.

Measuring Compartment Pressure

Where the diagnosis is uncertain (an unconscious or uncooperative patient), the intra-compartmental pressure can be measured directly. A pressure above about 30 mmHg, or a 'delta pressure' (diastolic blood pressure minus compartment pressure) below ~30 mmHg, supports the diagnosis and the need for fasciotomy. But in the alert patient, escalating pain out of proportion and pain on passive stretch are enough to act on — measurement should not delay treatment.

A High-yield Summary of the Trap

The reason compartment syndrome is so heavily examined and so dangerous is the trap of the late signs. A limb with an intact pulse and pink skin can still be undergoing irreversible muscle death, because the compartment pressure needed to strangle the muscles is well below the arterial pressure that maintains the pulse. The safe practice is to treat on the early clinical picture — disproportionate pain, worse on passive stretch — and never to be reassured by a present pulse; if in doubt, measure the pressure or proceed to fasciotomy.

Pulses remain palpable until very late — never wait for them to disappear.

• Raised pressure in a closed fascial compartment → occludes venous then capillary flow → ischaemia → muscle/nerve necrosis within hours.
• Causes: fractures, crush injury, reperfusion, tight cast/dressing, burns.
• 6 Ps: Pain (earliest, out of proportion, worse on passive stretch) + paraesthesia; pallor, paralysis, pulselessness, perishing cold are late.
• Pulses persist until late (compartment pressure < arterial) — don't wait for them.
• Emergency: remove constricting casts + urgent fasciotomy.