Compartment Syndrome

A freshly casted forearm with escalating pain unrelieved by opioids is not a pain management problem — it's a limb-threatening emergency with a closing treatment window.

Compartment syndrome occurs when pressure within a closed fascial compartment rises above capillary perfusion pressure (normal compartment pressure is 0–8 mmHg; syndrome develops when pressure exceeds 30 mmHg or is within 30 mmHg of diastolic blood pressure). Swelling from fractures, burns, tight casts, or crush injuries traps blood and fluid inside the compartment. As pressure climbs, capillary flow stops, and muscle and nerve ischemia begins. Irreversible damage starts within 4–6 hours. The hallmark assessment uses the 6 P's (pain, paresthesia, paralysis, pallor, pulselessness, poikilothermia), but pain is the earliest and most reliable sign — specifically, pain out of proportion to the injury that worsens with passive stretch of the affected muscles. Paresthesias follow. Pulselessness is a late, ominous finding meaning damage is already severe. Nursing priority: if you suspect compartment syndrome, immediately loosen or bivalve the cast, remove constrictive dressings, keep the limb at heart level (not elevated — elevation decreases arterial inflow to already ischemic tissue), and notify the surgeon stat. The definitive treatment is a fasciotomy, which the surgeon must perform urgently. Compartment pressure can be measured directly with a needle manometer, but clinical assessment should never wait for numbers.

Key Distinctions

Don't confuse compartment syndrome pain (worsens with passive stretch, unrelieved by analgesics) with expected postoperative fracture pain (improves with repositioning and analgesics). Students elevate the limb thinking it helps — elevation actually worsens ischemia; keep it at heart level. A palpable distal pulse does NOT rule out compartment syndrome; tissue death occurs at the capillary level long before arterial flow is lost.

Clinical Pearl

Pain out of proportion + pain on passive stretch = compartment syndrome until proven otherwise. Never wait for pulselessness — by then the tissue is already dying.