Sindrom Kompartemen

01Pathophysiology

Compartment syndrome develops when the pressure within a closed osseofascial compartment rises to a level that compromises local blood flow, resulting in tissue ischemia and, if untreated, irreversible necrosis. The fascial envelope surrounding each muscle compartment is non-compliant, meaning it cannot expand to accommodate increasing volume. When bleeding, edema, or external compression raises the intracompartmental pressure, venous outflow is obstructed first. This venous obstruction leads to further capillary congestion and transudation, creating a vicious cycle of worsening edema and rising pressure.

The critical concept is that arterial inflow is NOT occluded until very late in the process. This is why distal pulses are typically preserved until the syndrome is far advanced. Exam writers exploit this fact: a student who waits for pulselessness to diagnose compartment syndrome will miss the diagnosis entirely. The tissues undergo ischemia at the microvascular level long before large-vessel flow is interrupted.

The muscles and nerves within the compartment are the most sensitive to ischemia. Peripheral nerves develop dysfunction (paresthesias) within 30 minutes of ischemia, and irreversible muscle necrosis begins after roughly 6 hours of sustained elevated pressure. This is why the time window for fasciotomy is narrow and surgical delay is the most dangerous error a clinician can make.

Pain with passive stretch is explained directly by the pathophysiology: stretching ischemic muscle fibers provokes intense pain because the already-compromised tissue is mechanically stressed. This sign appears early and is the single most important clinical finding.

If compartment syndrome is left untreated, the end result is Volkmann ischemic contracture (in the forearm) or analogous contracture in the lower extremity, where necrotic muscle is replaced by fibrotic tissue, causing a fixed flexion deformity.

02Classification and Clinical Manifestation

The "6 P's" are a classic mnemonic, but they are listed in order of clinical appearance, and this sequence is heavily tested:

03Diagnostic Workup

Compartment syndrome is fundamentally a clinical diagnosis. The classic teaching is that when the presentation is clear (pain out of proportion, pain with passive stretch of the involved muscles, tense swelling, and a compatible history such as tibial fracture), you should proceed directly to fasciotomy without waiting for pressure measurements.

Intracompartmental pressure measurement using a Stryker device or arterial line transducer is reserved for situations where the clinical picture is uncertain. This includes obtunded patients (head injury, intoxication), intubated and sedated patients, uncooperative patients, and young children who cannot articulate their symptoms. In these populations, objective measurement becomes essential.

Two thresholds are used. An absolute compartment pressure $\ge 30mmHg\backslash geq\; 30\backslash \; mmHg$ is considered diagnostic. Alternatively, the delta pressure is calculated as $\mathrm{\Delta }P=\text{diastolic blood pressure}-\text{compartment pressure}\backslash Delta\; P\; =\; \backslash text\{diastolic\; blood\; pressure\}\; -\; \backslash text\{compartment\; pressure\}$. A delta pressure $\le 30mmHg\backslash leq\; 30\backslash \; mmHg$ indicates insufficient perfusion pressure and is considered a positive result. The delta pressure method is more physiologically accurate because it accounts for the patient's hemodynamic status: a hypotensive trauma patient with a compartment pressure of 25 mmHg may already be in danger, whereas that same pressure in a normotensive patient may be tolerated.

Serum CK is not used to diagnose compartment syndrome but rather to assess for rhabdomyolysis, a downstream complication. Do not confuse CK elevation with a diagnostic criterion for the syndrome itself.

04Management and Treatment

The single most important concept in management is that fasciotomy must not be delayed. Once the clinical diagnosis is made, or once compartment pressures confirm elevated readings in an equivocal case, the patient goes to the operating room. There is no role for conservative management, "watchful waiting," or serial exams in acute compartment syndrome. The window before irreversible damage is approximately 6 hours from onset.

During fasciotomy, the surgeon must release all compartments in the affected region, not just the one that appears most swollen. In the lower leg, a two-incision technique is standard: one incision along the anterolateral leg releases the anterior and lateral compartments, and a second medial incision releases the superficial and deep posterior compartments.

Fasciotomy wounds are intentionally left open. Attempting primary closure at the time of fasciotomy risks re-creating the elevated pressure. The wounds are covered with moist dressings and re-evaluated in 48 to 72 hours for delayed closure or split-thickness skin grafting if the tissues cannot be approximated.

If the patient presents very late (beyond 24 to 48 hours after onset) with an established, non-viable compartment, fasciotomy may paradoxically increase morbidity by introducing infection into necrotic tissue and causing reperfusion injury with systemic release of potassium, myoglobin, and acid. In this rare scenario, some sources advocate for non-operative management with planned amputation or debridement. This is an uncommon but testable concept.

For rhabdomyolysis, early and aggressive crystalloid resuscitation is the cornerstone. Normal saline or lactated Ringer's solution at a rate sufficient to produce urine output of $200mL\mathrm{/}hr200\backslash \; mL/hr$ (initially, then titrated to $100\text{-}200mL\mathrm{/}hr100\backslash text\{-\}200\backslash \; mL/hr$) is recommended. Urine alkalinization with sodium bicarbonate (target urine pH $>6.5>\; 6.5$) may reduce myoglobin cast formation, though evidence is mixed.

Contraindications and cautions:

• Mannitol may be used as an osmotic diuretic in rhabdomyolysis but should be used cautiously in patients with renal failure or anuria.

• Avoid potassium-containing IV fluids (e.g., lactated Ringer's) if the patient is already hyperkalemic; switch to normal saline.

• Do not use NSAIDs for pain control in rhabdomyolysis, as they worsen renal injury.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The most common way students get questions about compartment syndrome wrong is by waiting for late findings to make the diagnosis. Exam vignettes are designed to test whether you can recognize the syndrome at its earliest stage, when the only findings are pain out of proportion and pain with passive stretch. Students who are looking for the "classic" pulselessness or paralysis will either miss the diagnosis entirely or select the wrong answer because they think the presentation is incomplete.

A second frequent trap involves the role of pressure measurement. When the vignette presents a clear clinical picture (alert patient, obvious pain with passive stretch, tense compartment after a tibial fracture), the next best step is fasciotomy, not pressure measurement. Pressure measurement is only the correct answer when the patient cannot participate in the clinical exam (obtunded, intubated, pediatric).

Another tested concept is limb positioning. Students often reflexively choose to "elevate the extremity," which is standard teaching for reducing edema in most orthopedic injuries. In compartment syndrome, elevation above the heart decreases arterial perfusion pressure to the already-ischemic compartment and worsens the condition. The correct answer is to keep the limb at heart level.

Finally, watch for vignettes that describe a patient with a newly applied cast who develops worsening pain. The next best step is to remove the cast entirely (bivalve and spread), not to administer more analgesics. If pain persists after cast removal, proceed with compartment pressure measurement or fasciotomy. Test writers frequently use this scenario to distinguish students who understand the mechanical etiology from those who treat the symptom without addressing the cause.

The core competency being tested is the ability to recognize a time-sensitive surgical emergency based on early clinical findings, to sequence the diagnostic and therapeutic steps correctly (clinical exam first, pressure measurement only if exam is unreliable, fasciotomy without delay), and to avoid the common pitfalls of over-reliance on late signs or inappropriate conservative management.