Clinical meaning
Compartment syndrome is a limb-threatening emergency in which elevated pressure within a closed fascial compartment compromises perfusion to the muscles and nerves within that compartment. The normal resting compartment pressure is 0-8 mmHg; when pressure exceeds 30 mmHg (or is within 30 mmHg of diastolic blood pressure), microvascular perfusion is obstructed, causing tissue ischemia. The ischemic cascade involves muscle cell membrane dysfunction, sodium-potassium ATPase failure, cellular swelling, further pressure elevation, and progressive tissue necrosis. After 6-8 hours of sustained ischemia, irreversible muscle necrosis (rhabdomyolysis) and nerve damage occur. The six P's (Pain -- disproportionate to injury, worsened by passive stretch; Pressure -- compartment feels tense; Paresthesia; Paralysis; Pallor; Pulselessness) describe the progression, but pulselessness is a late finding because compartment syndrome obstructs capillary perfusion while arterial flow may be maintained. The nurse performs serial neurovascular assessments on at-risk patients (tibial and forearm fractures, crush injuries, tight casts, burns), recognizes that increasing analgesic requirements and pain with passive stretch of muscles within the compartment are the earliest and most reliable signs, removes any external compression (bivalve cast, release bandages), elevates the extremity to heart level (not above), and escalates urgently for emergent fasciotomy.