Clinical meaning
Acute compartment syndrome (ACS) is a limb-threatening and potentially life-threatening surgical emergency that occurs when pressure within a closed osseofascial compartment rises to a level that compromises the perfusion and viability of the tissues within that compartment. The pathophysiology involves a cascade of events that, if not interrupted by timely fasciotomy, leads to irreversible muscle necrosis (within 6-8 hours), nerve damage, rhabdomyolysis, renal failure, and potential limb loss or death. The registered nurse plays a pivotal role in early detection through serial neurovascular assessments, as compartment syndrome can progress from reversible ischemia to irreversible necrosis within hours.
The osseofascial compartment is an anatomical space bounded by bone and dense, inelastic fascia. The fascia's inability to expand is the fundamental problem in compartment syndrome -- it converts any increase in compartment volume or any decrease in compartment size into increased intracompartmental pressure (ICP). The lower leg has four compartments (anterior, lateral, superficial posterior, and deep posterior), the forearm has three compartments (volar/flexor, dorsal/extensor, and mobile wad), and the thigh has three compartments (anterior, posterior, and medial). The anterior compartment of the lower leg is the most commonly affected because it is the most tightly enclosed by fascial boundaries.
Normal intracompartmental pressure ranges from 0 to 8 mmHg. When ICP rises above 30 mmHg (or within 30 mmHg of the diastolic blood pressure, known as the delta pressure), the microcirculation within the compartment becomes compromised. It is critical to understand that compartment syndrome occurs at the capillary level, not at the level of major arteries. Arterial inflow continues even when compartment pressures are elevated because systolic arterial pressure (typically 120 mmHg) far exceeds the ICP. This is why distal pulses may remain palpable even in established compartment syndrome -- the absence of a distal pulse is a very late finding indicating complete vascular compromise. The pathology occurs at the arteriolar and capillary level: as ICP approaches the arteriolar pressure (approximately 30-40 mmHg), the arterioles collapse, eliminating perfusion to the capillary beds. Without capillary flow, oxygen delivery ceases, and the tissues within the compartment become ischemic.