Acute Compartment Syndrome: Why do we miss it, and how do we improve?

Author: Martin Yang, MD (EM Resident Physician, University of Kentucky) // Reviewed by: Courtney Cassella, MD (@corablacas); Alex Koyfman, MD (@EMHighAK); Brit Long, MD (@long_brit) 

The Case

A 35-year-old healthy young individual presents after an MVC. The patient had a prolonged extrication due to a pinned left leg under the steering column. Plain films demonstrate a left femur fracture. Fortunately, there are no other injuries on imaging. The trauma service was consulted for admission and orthopedics was consulted for management of his femur fracture. Repeated exams demonstrate an increasingly uncomfortable patient with an intact neurovascular exam. The patient complains of considerable thigh pain and is requiring escalating amounts of opioid pain medication. The admitting trauma service is aware, however is unable to evaluate the patient due to a complicated operative case. The bedside nurse approaches you for more pain medication orders. The easy thing to do would be to provide more pain medication with the assumption that the patient is under treated and defer further assessment to the primary team. However, that minor delay in care could result in lifelong consequences for this patient in the setting of acute compartment syndrome (ACS). In this review, we will discuss the etiology, general features, evaluation, and special considerations of this rather insidious and potentially devastating complication.

TL;DR (Too Long; Didn’t Read)

  • In the setting of uncontrolled pain or increasing pain medications, the clinician should consider ACS.


Trauma remains the most common setting for ACS, and fractures are the greatest single risk factor.[1] However, it is important to bear in mind that other etiologies can cause ACS. By definition, compartment syndrome arises from an increase in the compartment pressure which overcomes the diastolic pressure (as opposed to systolic pressure for which we would venture into the realm of limb ischemia).[1] This may result from increased volume within a compartment or reduced size of a compartment. An intracompartmental pressure (ICP) greater than the diastolic pressure initiates a potentially devastating snowballing effect of reduced capillary and lymphatic flow, venous outflow, and arterial inflow.[1] This leads to ischemic compromise which subsequently generates further edema all in a non-distensible compartment. With this in mind, ACS must be considered in patients who experience circumferential burns, snake bites, chronic anticoagulation, rhabdomyolysis, and Intravenous Drug Use (IVDU). However, this is hardly an exhaustive list.

Acute compartment syndrome is commonly associated with a fracture (up to 75%)[2] and 69% of cases occur secondary to a traumatic injury.[3] Prevalence favors lower extremities fractures with approximately 40% of ACS have an associated tibial fracture. Although tibial fractures demonstrate a significant association (positive predictive value ~ 11%)[2], this hardly excludes other areas, such as upper extremities, feet, and even lumbar spine. In fact, forearm fractures contributed to 18% of the population who ultimately received an ACS diagnosis.[2]


  • Trauma is the most common setting for ACS, but this is not exclusive.
  • Anything that can increase compartment pressure can lead to ACS.
  • General etiology of increased compartment pressure: hemorrhage/extravasation, inflammation/infection, foreign object.
  • Compartment pressure > diastolic pressure = Reduced capillary, lymphatic, venous flow = arterial compromise = tissue ischemia.


Once ACS is suspected, a thorough physical exam is needed. Compartment syndrome is a clinical diagnosis in the ED. If concerned for ACS based on history or exam, consultation with orthopedic surgery is recommended. Additionally, compartment pressures can be obtained if applicable. Pain with passive stretch of the isolated compartment is considered the most sensitive physical exam finding and should promptly be followed by surgical consultation.

For more information on the clinical findings see:

Compartment pressures can be measured directly with commercially available kits and can provide important diagnostic information. The utility of these pressures is, however, debatable. Normal compartment pressures are < 10 mmHg. Traditionally, an absolute pressure > 30 mmHg led to a fasciotomy.[1] However, this neglects the extremely varied patient specific tolerance of compartment pressures, systemic clinical contexts (i.e. hypotension), or other confounding patient specific cardiovascular/perfusion variances.

More recently, delta pressures have been utilized as a means of accounting for this in the decision to perform a fasciotomy. Delta pressures are calculated by subtracting the absolute compartment pressure from the diastolic blood pressure.

Delta Pressure = [Diastolic BP] – [Absolute Compartment Pressure] [4]

McQueen et al. attempted to provide some further clarity in the utility of delta pressures. They proposed a period of 24-hour monitoring with the threshold for fasciotomy being >2 sustained hours of <30 mmHg delta pressure. Ultimately, the study included 116 individuals with tibial fractures; only 3 of which received fasciotomies based on this criterion. Reportedly there were no overtreatments (unnecessary fasciotomies), no missed ACS diagnoses, and no sequelae noted on 15 month follow up.[5]


  • Pain with passive stretch is most sensitive, but difficult to discern from pain secondary to primary trauma.
  • Compartment pressures:
    • <10 mmHg normal
    • Absolute pressure >30 mmHg concerning for ACS, but not absolute in diagnostic criteria
  • Delta pressures may provide better indication for the need for fasciotomy.

Why do we miss it? / How do we improve?

ACS is frequently mentioned in initial discussions. Indeed, many will remember it a repeatedly highlighted teaching point in our medical school lectures.  So why is it such an easily missed diagnosis? To start, the diagnosis is fairly uncommon with an incidence of 1 to 7.9 per 100,000 population per year.[2] The dynamisms of such cases set within the confines of a busy emergency department and a lack of standardized initial screening assessment tools tend to set emergency providers up for failure. Understanding some of these pitfalls could help the provider avoid them.

Environmental / Cognitive Burden

Let us refer back to our initial case. One contributor to missed diagnosis is our environment and cognitive burden. Rarely can the environment of the emergency department be considered an advantage in patient care. For such insidious pathologies as ACS, this environment creates a significant clinical blind-spot. The cycles of head-spinning chaos interspersed by tense calm rarely takes into consideration the needs of our patients. His disposition is clear and inevitable. The five to six minutes it may take the ED provider to fully reassess the patient will take the provider away from another patient without a clear disposition. In a crowded department, it is easy to understand why another disposition would be prioritized. Nary an excuse, but more so an explanation, this situation does highlight that even from a workflow perspective, the emergency provider can be subconsciously disadvantaged.

How do we improve?

  • ACS is a dynamic diagnosis.
  • Despite a busy ED and lots of patients, frequent reassessments are necessary to fully make this diagnosis.

Anchoring Bias

Again referencing our case, as a seasoned resident, you reassess our patient and find that he is indeed in a great deal of pain. It is hard to argue that this is out of the ordinary, as this patient did suffer a femur fracture. Furthermore, after reviewing medical records available, the provider notes that the patient is on suboxone and has a strong history of opioid abuse, further complicating the patient’s pain management. Pain ubiquitously remains the first of the P’s that are frequented cited for ACS. Pain with passive stretch should increase suspicion. However, isolation of the affected compartment (although not in our specific case), especially in the smaller compartments of the hand and feet, may be difficult. Additionally as expected, pain itself is not reliable as a diagnostic tool with sensitivities ranging from 13% to 54%. In fact, clinical findings overall have sensitivities ranging from 13-64% as compared to ICP monitoring at 94%. [6] If a provider were to anchor onto increased tolerance to opioids or decreased pain tolerance as the cause for the patient’s increasing need for pain medication, this could create the cognitive bias that would lead to the correct ACS diagnosis and subsequently a delay in this patient’s care.

How do we improve?

  • Early and aggressive pain control.
  • Establish reliable baseline physical exam after pain control is achieved.
  • Reassess your differential diagnosis for the etiology of pain.

The Intubated Patient

The case obviously becomes even more skewed and problematic when patients are intubated and/or critically ill. A hypotensive trauma by definition will decrease the diastolic pressure which would adversely affect the threshold in which venous return becomes compromised leading to ACS.[1] In theory, appropriate resuscitation should leave hypotension as a transient complication. Identifying all injuries related to a trauma will help provide the needed context to consider ACS. If the patient is intubated, pain becomes an unmeasurable factor, removing a large tool in the ED physicians’ assessment of ACS. However, this can be overcome by a high index of suspicion after a thorough identification of all injuries as emphasized previously. Intracompartmental monitoring has been show to assist in the decision for fasciotomy as shown by a sensitivity of 94%.[6]

How do we improve?

  • Thorough account of all injuries => really highlights the importance of the secondary and tertiary survey
  • Intubated patients provide special challenges: unreliable exams, relative hypotension, patient unable to vocalize changes
  • Rely on consideration of diagnosis and ICP monitoring


Even from these specific examples, a multitude of traps are apparent for the EM physician. Additionally, lack of useful screening tools, systems issues, and other cognitive biases increase the complexity of ACS. Although definitive diagnosis and management may be decided by consultants, our vigilance and advocacy are crucial.  The emergency physician should provide a reliable initial baseline exam, consider this diagnosis, reassess escalating pain, and more importantly pursue aggressive patient advocacy and management.

Management / Complications

The management of ACS is less difficult than diagnosis. As discussed previously, absolute pressures >30 mmHg may be an indication for urgent fasciotomy. However, equivocal pressures can provide baseline information for the admitting team. Once the diagnosis is made or suspicion is high, an immediate surgical consultation will be necessary. If possible, place limb at the level of the heart or slightly dependent. In the setting of immobilization, immediately remove or bivalve the cast or splint to decompress the compartment.

Complications of ACS include rhabdomyolysis, hyperkalemia, and acute kidney injury. In the setting of suspected ACS, basic metabolic panel, creatinine kinase, urinalysis, and EKG are appropriate to screen for these complications. Larger compartments (lumbar, lower extremity) will proportionally contribute more to these complications by causing higher degrees of rhabdomyolysis. Have an increased index of suspicion in patients with pre-existing kidney disease or history of renal failure. Monitoring urine output may not be immediately beneficial, but could assist the inpatient team with fluid status monitoring.

Aggressive fluid resuscitation may be necessary for two reasons: treatment of rhabdomyolysis and subsequent acute kidney injury and augmentation of compartment vascular pressures of hypotensive patients to increase the threshold for ACS.

Finally, treat pain with opioid and non-opioid analgesics. Avoid ketorolac or NSAIDs given the possible impairment of renal function.

Take Home Points:

  • 5 Ps = PAIN, pallor, paresthesia, paralysis, pulselessness
  • Increasing pain despite analgesia should increase suspicion for ACS.
  • Passive stretch of compartment thought to be most sensitive exam finding.
  • Compartment pressures: <10 mmHg normal, >30 mmHg concerning for ACS
  • Consider use of delta pressure for monitoring in equivocal exams.
  • Special consideration with hypotensive patients, lower pressures required to overcome arterial pressures.
  • Treat associated rhabdomyolysis, hyperkalemia, and acute kidney injury.

References/Further Reading:

  2. Ferri FF (2017).Ferri’s Clinical Advisor 2018 E-Book: 5 Books in 1. Elsevier Health Sciences. p. 317. ISBN 9780323529570.
  3. McQueen MM, Gaston P, Court-Brown CM. Acute compartment syndrome: who’s at risk? J Bone Joint Surg [Br] 2000;82-B:200-3.
  4. Elliott, KGB. Diagnosing acute compartment syndrome. J Bone Joint Surg Br. 2003 Jul;85(5):625-32.
  5. McQueen et al. Compartment Monitoring in Tibial Fractures. J Bone Joint Surg. 1996;78-B:99-104
  6. McQueen MM, Duckworth AD. The diagnosis of acute compartment syndrome: a review.Eur J Trauma Emerg Surg. 2014;40(5):521-528. doi:10.1007/s00068-014-0414-7


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