Written by: Jesus Trevino, MD (EM Resident Physician, PGY-2, NUEM); Edited by: Adnan Hussain, MD (EM Resident Physician, PGY-4, NUEM); Expert Commentary by: Matt Levine, MD
Introduction
Acute compartment syndrome (CS) of the extremity is a clinical diagnosis. However, patients without the ability to convey a good history (e.g., children, altered mental status/intubated patients) increase our reliance on objective measures of compartment syndrome. This post will review:
- Characteristics of CS injuries by mechanism and location
- Utility of clinical symptoms
- Utility of compartment pressures in the diagnosis of CS
Mechanisms and Locations
CS is typically associated with fractures. However, other injuries can predispose patients to sufficient tissue damage and swelling that may culminate in this condition. These injuries include (Adams):
- Circumferential burns
- Soft tissue infections
- Crush injury
- Hematomas
- Rhabdomyolysis
- Envenomations
- Iatrogenic (e.g, casts, infiltrated PIV with high-rate infusions)
Regarding fractures, the incidence of CS increases with fracture severity (Adams):
- closed: 1.2%,
- open: 6%,
- co-existing vascular injury: 19%
In terms of the distribution of CS injury, a case review series of 164 patients reported the following major injuries leading to this condition (McQueen 2000):
Evidence Behind the H&P Findings
The textbook teaching on the diagnosis of CS hinges on the 5 “P”s:
Pain
Paresthesias
Pallor
Pulselessness
Paralysis
A review article identified four studies of CS that reported the presence or absence of symptoms (i.e., pain, paresthesias, pain with passive stretch or PPS, paresis) in operative patients and calculated aggregated sensitivities and specificities (Ulmer 2002):
At first glance, this data demonstrates that these clinical symptoms and signs uniformly offer poor sensitivity for the diagnosis of CS. On the other hand, the above sensitivities should make you pause and wonder if these low test statistics are truly valid. For instance, common sense would dictate a higher sensitivity for pain, right? It turns out the original papers included in Ulmer’s analysis defined CS cases based on absolute compartment pressure rather than gross surgical findings (e.g., muscle necrosis, difficulty closing compartments post-fasciotomy). Consequently, many cases were liberally categorized as CS which inflated the cases of false negatives and resulted in lower sensitivities for the above clinical findings.
Overall, the literature lacks high-quality evidence to support or refute the use of the 5 “P”s.
Rationale and Evidence Behind Compartment Pressures Measurements
Now that we have reviewed the utility of the history and physical for the work-up of CS, we turn to additional objective measures - compartment pressures. Theoretically, compartment syndrome occurs when compartment pressures rise above the capillary perfusion pressure (i.e., 20-30 mmHg) resulting in decreased perfusion, increased tissue ischemia and increased swelling - a negatively reinforcing cycle leading to worsening compartment pressures and limb viability. Therefore, it is logical to expect that compartment pressures > 30 mmHg can provide objective evidence of compartment syndrome, right? Hold that thought...
In a prospective study of 97 patients with tibial fracture and concern for compartment syndrome, intra-compartment pressure (ICP) and perfusion pressure (diastolic pressure less intra-compartment pressure, PP) measurements revealed (Janzing 2001):
§ Likelihood ratios (LR) are an application of sensitivity/specificity information to aid our clinical decision making. See Incorporating Diagnostic Testing Into Your Clinical Decisions for a primer on LRs.
Overall, ICP > 30 mmHg offered a decent sensitivity for detection of CS; however, PP < 30 mmHg offered increased specificity and demonstrated superior LRs. Another prospective study of patients with tibial fractures compared a group with elevated ICP > 30 mmHg, for more than 6 hours, against a group with normal ICP and found no clinical difference (muscle strength and return to function) at 12 month follow-up which reinforces the idea that PP is a more meaningful measure of CS than ICP (White 2003).
Building on the finding that PP is a more useful test for CS evaluations, a retrospective study looked at continuous compartment pressure measurements and whether PP < 30 mmHg for at least 2 hours could improve the diagnostic accuracy of this test and showed: sensitivity 0.94, specificity 0.98, LR+59.8, LR- 0.06 (McQueen 2013).
Summary
Acute compartment syndrome:
- Remains a clinical diagnosis
- Occurs most often from fractures, especially tibial diaphyseal fractures, though can also occur secondary to a variety of soft tissue injuries
- Evaluation can be supplemented by compartment pressures; perfusion pressure < 30 mmHg has better diagnostic accuracy than absolute intra-compartment pressure.
Expert Commentary
The scenario of painful swelling after trauma can be a predicament for the emergency physician. Is this a compartment syndrome (CS)? Can I clinically rule out a CS? Should I check a compartment pressure? Dr. Trevino did an excellent job digging up some data to help answer these questions.
We all learned the “5 P’s” in medical school. But the idea is to make the diagnosis while muscle is still salvageable, and if you wait for all 5 P’s to appear, you will miss your window to intervene and save viable tissue. That is why index of suspicion must be high.
The classic CS presents with tense painful swelling and pain on passive stretch of the muscle that goes through the compartment. If the clinical exam is suspicious enough, the case can proceed to fasciotomy without confirmatory testing. It sounds more straightforward, however, than it often is in clinical practice. An orthopedic surgeon has typically seen and treated more CS than an individual emergency physician so their clinical evaluation of the tenseness of the compartment and pain on ranging is certainly helpful in uncertain cases. Clinical uncertainty can also be addressed by checking the compartment pressure. For a great demonstration of how to check compartment pressure, see this video by NU EM Residency Alum John Sarwark and current EM resident Michael Macias:
As Dr. Trevino demonstrated, this reading should be used to calculate the perfusion pressure (PP = Diastolic BP minus Compartment Pressure). This leaves you with three pieces now to rule in or rule out CS: clinical exam, compartment pressure and perfusion pressure. If you are still not sure, then the patient needs observation on the orthopedic service, or better yet, fasciotomy.
Working in a busy trauma center, the most common CS scenarios I have encountered in the last 15 years are long bone fractures and GSWs. I’ve seen CS in less traditional locations when skin poppers/IV drug users inject too much volume into a small compartment (i.e. in the hand). Current NU EM resident Sarah Sanders recently constructed a nice CS case for our residency’s Orthopedics Teaching File based on one of our cases.
So, residents, find your department’s compartment pressure manometer (often the brand Stryker) and figure out how you would use it by watching the video link so you will be prepared for the real thing! And remember, CS is a clinical diagnosis that is suspected in the setting of a swollen painful compartment and pain out of proportion when a muscle in the compartment is passively stretched.
Matthew R Levine, MD
Assistant Professor
Director of Trauma Services, Department of Emergency Medicine
Northwestern Memorial Hospital
Other Posts You May Enjoy
How To Cite This Blog Post
[Peer-Reviewed, Web Publication] Trevino J, Hussain A (2017, April 18). Acute Compartment Syndrome [NUEM Blog. Expert Commentary By Levine M]. Retrieved from http://www.nuemblog.com/blog/compartment-syndrome
References
- Adams, J. Emergency Medicine. 2nd ed. Philadelphia: Saunders/Elsevier; 2008. Chapter 91, Acute Compartment Syndromes, Peak D; p. 797-800.
- McQueen MM, Gaston P, Court-Brown CM. Acute compartment syndrome. Who is at risk? J Bone Joint Surg Br. 2000 Mar;82(2):200-3.
- Ulmer T. The clinical diagnosis of compartment syndrome of the lower leg: are clinical findings predictive of the disorder? J Orthop Trauma. 2002 Sep;16(8):572-7.
- Janzing HM, Broos PL. Routine monitoring of compartment pressure in patients with tibial fractures: Beware of overtreatment! Injury. 2001 Jun;32(5):415-21.
- White TO, Howell GE, Will EM, Court-Brown CM, McQueen MM. Elevated intramuscular compartment pressures do not influence outcome after tibial fracture. J Trauma. 2003 Dec;55(6):1133-8.
- McQueen MM, Duckworth AD, Aitken SA, Court-Brown CM. The estimated sensitivity and specificity of compartment pressure monitoring for acute compartment syndrome. J Bone Joint Surg Am. 2013 Apr 17;95(8):673-7.