Is delta pressure accurate for compartment syndrome?

As you sit down at your workstation to finally catch up on some of those notes you’ve been putting off until the end of your shift, one of the nurses comes to notify you… “You remember that patient in room 4 with the leg pain? This is her urine…”

You take a quick look over and immediately appreciate her concern. She’s holding a sample of urine that’s so dark, it looks like it came straight out of that Coca-Cola(TM) bottle you have sitting on your desk! You immediately review her presentation… “68-year-old woman with cerebral palsy, normally ambulatory, presenting with left lower extremity pain, swelling, and difficulty walking. Her ‘legs buckled’ and she fell while trying to sit down earlier that morning. Her lower leg is slightly tense, tender, with no neurological deficits.” After you send off some urine and blood tests to evaluate for the underlying etiology, you head back to room 4 and re-evaluate your patient…

Figure 1: Rhabdomyolysis urine(1)

You confirm that the left lower extremity is tense, but now she’s complaining of paresthesia and some numbness in that extremity as well. Suspecting compartment syndrome, you decide to get your surgical colleagues involved right away, recognizing that time means tissue!

…Is this compartment syndrome? Is there a single, definitive test to confirm our suspicion? As we review the literature on compartment syndrome, we will recognize that diagnosis still comes with great difficulty, but the consequences of misdiagnosis are severe.

What is acute extremity compartment syndrome?

Having been recognized for over 100 years, the pathophysiology of compartment syndrome is quite well understood. The compartments of the extremities are are separated by fascia. An insult, usually trauma, causes tissue destruction in one of the compartments. This leads to an increase in the intra-compartmental pressure, which decreases tissue perfusion and oxygenation leading to further tissue destruction.(2)

Figure 2: Graphical representation of compartment syndrome(2)

What causes compartment syndrome?

Theoretically, anything leading to an acute destruction of tissue within a compartment or introduction of extra fluid, such as blood, into the compartment can set off this spiral of further tissue destruction. The majority of cases occur following trauma, especially with associated fracture.(2) The remaining cases involve numerous etiologies: constricting devices such as casts, circumferential burns, infection of local tissue, rhabdomyolysis, bleeding, direct compression for prolonged periods, and even iatrogenically from injected substances.(3-6)

How do we diagnose compartment syndrome?

This is where the clinical challenge lies, and where inconsistency and controversy within the literature start to set in. The diagnosis can be made by history and physical alone, measurement of compartmental pressures (either spot measurements or continuously), or a combination of both. However, the only true confirmation of acute compartment syndrome occurs when 1) a fasciotomy is performed and the presence of bulging muscle tissue with necrosis is visualized or 2) the patient develops the irreversible neurological/muscle damage months after the initial insult.

Classically, we are taught that compartment syndrome presents with pallor, pain out of proportion with exam, pain on passive stretch, paresthesia, and paresis.(2) Ulmer attempted to determine the sensitivity and specificity of these clinical findings with a systematic review in 2002.(7) He argued that the sensitivity of the individual findings is low, but specificity is high. When more than one of these findings are present, the likelihood of compartment syndrome is very high.(7) Additionally, the diagnosis can become tricky when the patient is unconscious or cannot communicate the most important early symptom of severe pain.(2)

When the clinical suspicion is not so clear or in pediatric cases, many clinicians turn to either static or dynamic methods to directly measure compartment pressures. Normal compartment pressures in adults are approximately 8 mm Hg, and in children it ranges from 10-15 mm Hg.(2,8) The absolute value of compartment pressure is typically not useful, as the tissue perfusion can depend also on the patient’s diastolic pressure. When pressures are measured, the delta pressure (Δp or diastolic pressure – intra-compartmental pressure) proves more useful. A delta pressure of <30 mm Hg is suggestive of compartment syndrome.(8-10) Additionally, many have argued that continuous compartment pressure monitoring is more important than single static measurements, as single measurements may lead to unnecessary fasciotomies.(10) The methods for performing pressure measurements include arterial line transducer systems, slit catheters, and self-contained pressure measurement systems (StrykerTM system).(11)

A quick look at the evidence for continuous pressure monitoring shows inconsistent results. McQueen et al report that continuous compartment measurement with a Δp <30 mm Hg for 2 hours yields a positive likelihood ratio of 47 and a negative likelihood ratio of 0.06 for compartment syndrome.(12) However, this was a retrospective single center review with well-established protocols, and the study does not specify if pressure measurement was the sole indication for fasciotomy. A 2006 randomized controlled trial showed that routine continuous compartment pressure monitoring in tibial fractures was not useful in determining the need for fasciotomy.(13) In this trial, all patients who would have met pressure criteria for fasciotomy (Δp <30 mmHg on continuous monitoring) did not show any other signs of compartment syndrome, so no procedure was performed. These patients subsequently had no neurological sequelae at follow-up.(13,14)

Based on current research, diagnosis of compartment syndrome is still best determined by clinical evaluation and serial examination. Compartment pressure measurement may be a useful adjunct, but its use should be cautioned, and routine use may be detrimental, leading to unnecessary fasciotomies. More research is necessary to define clear clinical diagnostic tools and determine a standard that may prove ideal. There is research being performed on new non-invasive technology such as near-infrared spectroscopy to indirectly measure tissue perfusion, but this is still in its infancy.(2)

Treatment of acute extremity compartment syndrome

Although accurate diagnosis can be difficult, once it is made, the treatment of acute compartment syndrome is well established. Fasciotomy with release of all compartments in the respective extremity is performed. The importance of releasing all compartments is emphasized, as failure to do so may still result in neurological and vascular compromise.(2,15,16) Complications associated with fasciotomy can include infection, delayed healing, prolonged hospital stays, and persistent pain at fasciotomy sites.(15)

A typical method for performing fasciotomy of the lower leg is depicted below.

Figure 3: Two incision technique of lower leg fasciotomy(16)

Back to our patient

Following surgical evaluation of our patient, the diagnosis of acute extremity compartment syndrome was agreed upon, and the patient was taken urgently to the OR for fasciotomy. Upon incision (as above), the surgeons noted bulging of the tissue in the anterior and lateral compartments.

What was the cause of our patient’s compartment syndrome? The exact etiology remains unclear, but given the lack of significant trauma to the extremity, a cycle of rhabdomyolysis and tissue necrosis remains the likely culprit. The patient’s known diagnosis of cerebral palsy may have contributed to this process with spasticity of the respective muscles being an important inciting trigger.

In summary, compartment syndrome has many potential causes, but acute extremity trauma with fracture remains the leading cause. Diagnosis is determined clinically with history and physical exam, but intra-compartment pressure measurement may be useful in equivocal cases. This needs to be used with caution, however, and may lead to overdiagnosis. Regardless, in suspected cases, continuous monitoring and reassessment remains key. Treatment with fasciotomy to release all compartments remains standard of care but comes with its own risks and complications.

References

1. Heilman J. RhabdoUrine. Wikipedia. https://commons.wikimedia.org/wiki/File:RhabdoUrine.JPG.
2. von Keudell AG, Weaver MJ, Appleton PT, et al. Diagnosis and treatment of acute extremity compartment syndrome. Lancet. 2015;386(10000):1299-1310.
3. Brinley A, Chakravarthy B, Kiester D, Hoonpongsimanont W, McCoy CE, Lotfipour S. Compartment Syndrome with Rhabdomyolysis in a Marathon Runner. Clinical practice and cases in emergency medicine. 2018;2(3):197-199.
4. Connes P. Sickle cell trait, exertional rhabdomyolysis, and compartment syndrome. Lancet. 2015;385(9981):1948.
5. Hope MJ, McQueen MM. Acute compartment syndrome in the absence of fracture. J Orthop Trauma. 2004;18(4):220-224.
6. Parekh R, Care DA, Tainter CR. Rhabdomyolysis: advances in diagnosis and treatment. Emergency medicine practice. 2012;14(3):1-15; quiz 15.
7. Ulmer T. The Clinical Diagnosis of Compartment Syndrome of the Lower Leg: Are Clinical Findings Predictive of the Disorder? Journal of Orthopaedic Trauma. 2002;16(8):572-577.
8. Shadgan B, Menon M, O’Brien PJ, Reid WD. Diagnostic Techniques in Acute Compartment Syndrome of the Leg. Journal of Orthopaedic Trauma. 2008;22(8):581-587.
9. Whitesides TE, Haney TC, Morimoto K, Harada H. Tissue pressure measurements as a determinant for the need of fasciotomy. Clinical orthopaedics and related research. 1975(113):43-51.
10. Whitney A, O’Toole RV, Hui E, et al. Do one-time intracompartmental pressure measurements have a high false-positive rate in diagnosing compartment syndrome? J Trauma Acute Care Surg. 2014;76(2):479-483.
11. Boody AR, Wongworawat MD. Accuracy in the measurement of compartment pressures: a comparison of three commonly used devices. The Journal of bone and joint surgery American volume. 2005;87(11):2415-2422.
12. McQueen MM, Duckworth AD, Aitken SA, Court-Brown CM. The estimated sensitivity and specificity of compartment pressure monitoring for acute compartment syndrome. The Journal of bone and joint surgery American volume. 2013;95(8):673-677.
13. Harris IA, Kadir A, Donald G. Continuous compartment pressure monitoring for tibia fractures: does it influence outcome? J Trauma. 2006;60(6):1330-1335; discussion 1335.
14. Nelson JA. Compartment pressure measurements have poor specificity for compartment syndrome in the traumatized limb. J Emerg Med. 2013;44(5):1039-1044.
15. Olson SA, Glasgow RR. Acute compartment syndrome in lower extremity musculoskeletal trauma. The Journal of the American Academy of Orthopaedic Surgeons. 2005;13(7):436-444.
16. McLaughlin N, Heard H, Kelham S. Acute and chronic compartment syndromes: know when to act fast. JAAPA : official journal of the American Academy of Physician Assistants. 2014;27(6):23-26.

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• Is delta pressure accurate for compartment syndrome? - February 13, 2019