The clinical case A healthy 35-year-old young individual presents after a motor vehicle accident. The patient had a prolonged extrication due to a left leg trapped under the steering column. Plain x-rays show a fracture of the left femur . Fortunately, there are no other injuries in the images. He consulted the trauma service for admission and for the management of his femur fracture. Repeat examinations demonstrate an increasingly uncomfortable patient with an intact neurovascular examination. The patient complains of considerable pain in the thigh and requires increasing amounts of opioid analgesics. The admitting trauma service is aware, however, they are unable to evaluate the patient due to a complicated surgical case. The bedside nurse approaches you to ask for more pain medications. The easiest thing to do would be to provide more analgesics with the assumption that the patient is on treatment and defer further evaluation to the primary team. However, that small delay in care could have lifelong consequences for this patient in the setting of acute compartment syndrome (ACS). In this review, we will discuss the etiology, general characteristics, evaluation, and special considerations of this rather insidious and potentially devastating complication. |
Etiology
Trauma remains the most common scenario for ACS and fractures are the single largest risk factor. However, it is important to note that other etiologies can cause SCA.
By definition, compartment syndrome arises from an increase in compartment pressure that exceeds diastolic pressure (as opposed to systolic pressure for which we would venture into the realm of limb ischemia ). This may be due to a larger volume within a compartment or a reduced size of a compartment.
An intracompartmental pressure (ICP) greater than the diastolic pressure initiates a potentially devastating snowball effect of reduced capillary and lymphatic flow, venous outflow, and arterial inflow. This leads to ischemic compromise that subsequently generates more edema all in a non-compliant compartment .
With this in mind, ACS should be considered in patients experiencing circumferential burns, snake bites, chronic anticoagulation, rhabdomyolysis, and intravenous drug use (IVDU). However, this is not an exhaustive list.
Acute compartment syndrome is commonly associated with a fracture (up to 75%) and 69% of cases are secondary to traumatic injury. The prevalence favors lower extremity fractures with approximately 40% of SCAs having an associated tibial fracture. Although tibia fractures demonstrate a significant association (positive predictive value ~11%), this hardly excludes other areas, such as the upper extremities, feet, and even the lumbar spine. In fact, forearm fractures contributed to 18% of the population ultimately receiving a diagnosis of ACS.
Summary
- Trauma is the most common scenario for SCA, but this is not exclusive.
- Any cause that can increase compartment pressure can cause SCA.
- General etiology of increased compartment pressure: hemorrhage/extravasation, inflammation/infection, foreign body.
- Compartment pressure > diastolic pressure = reduced capillary, lymphatic and venous flow = arterial compromise = tissue ischemia.
Assessment
Once SCA is suspected, a complete physical examination is needed. Compartment syndrome is a clinical diagnosis in the emergency department. If you are concerned about ACS based on history or examination, consultation with orthopedic surgery is recommended. Additionally, compartment pressures can be obtained if applicable. Pain with passive stretching of the isolated compartment is considered the most sensitive finding on physical examination and should be immediately followed by surgical consultation.
Compartment pressures can be measured directly with commercially available kits and can provide important diagnostic information. However, the usefulness of these pressures is debatable. Normal compartment pressures are <10 mmHg. Traditionally, an absolute pressure > 30 mmHg led to a fasciotomy. However, this overlooks the extremely varied patient-specific tolerance to compartmental pressures, systemic clinical contexts (i.e., hypotension), or other confounding patient-specific cardiovascular/perfusion variations.
More recently, delta pressures have been used as a means to account 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 Compartmental Pressure] [4]
McQueen et al. attempted to provide more clarity on the usefulness of delta pressures. They proposed a 24-hour monitoring period with a threshold for fasciotomy of >2 hours of sustained <30 mmHg delta pressure. Finally, the study included 116 people with tibial fractures; only 3 of whom received fasciotomies based on this criterion. Reportedly, there were no overtreatments (unnecessary fasciotomies), no ACS diagnoses were missed, and no sequelae were observed at the 15-month follow-up.
Summary
- Pain with passive stretching is more sensitive, but difficult to differentiate from pain secondary to primary trauma.
- Compartment pressures:
<10 mmHg normal
Absolute pressure >30 mmHg concerning for ACS, but not absolute in the diagnostic criteria.
Delta pressures may provide a better indication of the need for a fasciotomy.
Why do we overlook it? / How do we improve?
SCA is frequently mentioned in initial discussions. In fact, many will remember it as a teaching point repeatedly made in our medical school lectures. So why is it such an easy diagnosis to miss?
To begin with, the diagnosis is quite rare with an incidence of 1 to 7.9 per 100,000 population per year. The dynamics of such cases set within the confines of a busy emergency department and the 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 load
Let’s go back to our initial case. One factor that contributes to missed diagnosis is our environment and cognitive load. In rare cases, the ED environment can be considered an advantage in patient care. For pathologies as insidious as ACS, this environment creates a significant clinical blind spot . Cycles of dizzying chaos interspersed by tense calm rarely take into account the needs of our patients. Its disposition is clear and inevitable. The five to six minutes it may take the ED provider to completely reassess the patient will distance the provider from another patient without a clear disposition. In a crowded apartment, it’s easy to understand why another layout would be prioritized. Not an excuse, but more than an explanation, this situation highlights that even from a workflow perspective,
How do we improve?
ACS is a dynamic diagnosis. Despite a busy ED and many patients, frequent reevaluations are needed to make this complete diagnosis.
Anchor bias
Again referring to our case, as an experienced resident, you re-evaluate our patient and discover that he is, in fact, in a lot of pain. It is difficult to argue that this is out of the ordinary, as this patient suffered a femur fracture. Additionally, after reviewing available medical records, the provider notes that the patient is taking suboxone and has a strong history of opioid abuse, further complicating the patient’s pain management. Pain remains ubiquitously the first of the frequently cited Ps for ACS.
Pain with passive stretching should raise suspicion.
However, isolation of the affected compartment (although not in our specific case), especially in the smaller hand and foot compartments, can be difficult. Furthermore, as expected, pain itself is unreliable as a diagnostic tool with sensitivities ranging from 13% to 54%. In fact, clinical findings generally have sensitivities ranging from 13 to 64% compared with ICP monitoring at 94%.
If a provider relied on higher opioid tolerance or lower pain tolerance as the cause of the patient’s increased need for pain medications, this could create the cognitive bias that would lead to the correct diagnosis of ACS and subsequently to a delay in this patient care.
How do we improve?
- Early and aggressive pain control.
- Establish a reliable baseline physical examination after achieving pain control.
- Reevaluate your differential diagnosis for the etiology of the pain.
The intubated patient
Obviously, the case becomes even more skewed and problematic when patients are intubated and/or in critical condition. Hypotensive trauma, by definition, will decrease diastolic pressure, which would negatively affect the threshold at which venous return is compromised and leads to ACS. In theory, adequate resuscitation should leave hypotension as a transient complication.
Identifying all trauma-related injuries will help provide the necessary context for considering SCA. If the patient is intubated, pain becomes an unmeasurable factor, eliminating a great tool in the evaluation of ACS by emergency department physicians.
However, this can be overcome with a high index of suspicion after thorough identification of all lesions, as highlighted above. Intracompartmental monitoring has been shown to assist in the decision to perform a fasciotomy, as demonstrated by a sensitivity of 94%.
How do we improve?
- Complete reporting of all injuries => really highlights the importance of secondary and tertiary survey.
- Intubated patients present special challenges: unreliable examinations, relative hypotension, patient unable to vocalize changes.
- Trust consideration of ICP diagnosis and monitoring
Even from these specific examples, a multitude of pitfalls are evident to the ER physician. Additionally, the lack of useful screening tools, systems issues, and other cognitive biases increase the complexity of SCA.
Although consultants can decide the definitive diagnosis and management, our vigilance and advocacy are crucial. The emergency physician should provide a reliable initial baseline examination, consider this diagnosis, reevaluate increasing pain, and, most importantly, pursue aggressive patient advocacy and management.
Management/Complications
The management of ACS is less difficult than the diagnosis. As previously discussed, absolute pressures >30 mmHg may be an indication for urgent fasciotomy . However, equivocal pressures can provide baseline information for the intake team.
Once the diagnosis is made or suspicion is raised, an immediate surgical consultation will be necessary. If possible, place the limb at heart level or slightly dependent. In case 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 (CPK), urinalysis, and electrocardiogram are appropriate to detect these complications. Larger compartments (lumbar, lower extremities) will contribute proportionally more to these complications by causing higher degrees of rhabdomyolysis.
Have a higher index of suspicion in patients with pre-existing kidney disease or a history of kidney failure. Monitoring urine output may not be of immediate benefit, but could help the inpatient team monitor fluid status.
Aggressive fluid resuscitation may be necessary for two reasons:
- The treatment of rhabdomyolysis and subsequent acute kidney injury.
- Increasing compartmental vascular pressures of hypotensive patients to increase the ACS threshold.
Finally, treat pain with opioid and non-opioid pain relievers. Avoid ketorolac or NSAIDs given the possible deterioration of renal function.
Highlights:
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