Approach Considerations
In a patient with the classic compartment syndrome presentation and physical examination findings, no laboratory workup is needed. Laboratory results are often normal, are not necessary to diagnose compartment syndrome, and are not helpful to rule out compartment syndrome. However, in acute compartment syndrome, especially with trauma, consider performing a workup for rhabdomyolysis, with measurement of the following:
-
Creatine phosphokinase (CPK)
-
Renal function studies
-
Urinalysis
-
Urine myoglobin
A CPK concentration of 1000-5000 U/mL or greater or the presence of myoglobinuria can suggest compartment syndrome. Serial CPK measurements may show rising levels indicative of a developing compartment syndrome. Urinalysis may be used to help identify causes of acute renal failure.
Patients with rhabdomyolysis should have serum chemistry studies done. Complete blood cell count and coagulation studies should be part of the preoperative workup. Anemia worsens tissue oxygenation. Disseminated intravascular coagulation is a rare but possible complication.
Measurement of intracompartmental pressures remains the standard for diagnosis of compartment syndrome. Perform this procedure as soon as a diagnosis of compartment syndrome is suspected.
Imaging studies are usually not helpful in making the diagnosis of compartment syndrome. However, such studies are used in part to eliminate disorders in the differential diagnosis. Standard radiographs are obtained to determine the occurrence and nature of fractures. Stress fractures and periostitis can be diagnosed with plain radiographs, bone scans, computed tomography (CT) scans, or magnetic resonance imaging (MRI) scans. [64] CT scanning may be useful if pelvic or thigh compartment syndrome is part of the differential diagnosis.
Muscle tears can be observed using MRI or ultrasonography. [12] MRI may show increased signal intensity in an entire compartment on T2-weighted, spin-echo sequences. Doppler ultrasound may be used to evaluate arterial flow and to rule out deep venous thrombosis, particularly in the lower extremities. In addition, the loss of normal phasic patterns of tibial venous blood flow has been shown to accurately predict the need for surgical fasciotomy. [65] Ultrasonography alone is not useful in diagnosing compartment syndrome, but it aids in the exclusion of other disorders.
In the lower leg, partial vascular occlusion may cause a pseudo–compartment syndrome. Angiography may be needed to exclude adductor canal compression syndrome and popliteal artery entrapment. Pulse oximetry is helpful in identifying limb hypoperfusion. However, it is not sensitive enough to exclude compartment syndrome. In unusual cases, muscle biopsies may be necessary in primary muscle disorders. Histology is usually not helpful, but if necrotizing fasciitis is in the differential diagnosis, intraoperative cultures and a Gram stain may be of benefit.
Renal Function and Serum Chemistry Studies
Blood urea nitrogen (BUN) and creatinine levels are used to assess the patient's hydration status in cases of rhabdomyolysis. Measurement of the potassium level is needed in cases of rhabdomyolysis, as severe hyperkalemia may result in a wide-complex, possibly fatal arrhythmia. Purines released from cell nuclei result in hyperuricemia and nephrotoxicity. Coexisting oliguria, aciduria, and uricosuria worsen nephrotoxicity.
An anion gap (see the Anion Gap calculator) may indicate other underlying etiologies (eg, drug overdose) for the compartment syndrome. Sodium, potassium, bicarbonate, and phosphate levels are used to assess lactic acidosis and other metabolic acids. In addition, hyperphosphatemia aggravates hypocalcemia. Metastatic calcification is possible.
Compartment Pressure Measurement
Various methods and equipment can be used for compartment pressure measurement. A transducer connected to a catheter usually is introduced into the compartment to be measured. This is the most accurate method of measuring compartment pressure and diagnosing compartment syndrome. Measurement of the compartment pressure then can be performed at rest, as well as during and after exercise. With the acute syndrome, the exact pressure threshold is controversial, but typical ranges are from 30-45 mm Hg at rest. Some sources state that it is better to associate this pressure to diastolic pressure (that is, within 10-30 mm Hg of diastolic pressure).
Injection technique of direct pressure measurement
Direct compartment-pressure measurement is the diagnostic criterion standard and should be the first priority if the diagnosis is in question. A number of handheld devices are available. The Stryker pressure tonometer is widely used, and pressure measurements from the Stryker device are within 5 mm Hg of the slit catheter for 95% of all readings (direct communication with Stryker Corporation, April 2007). The Stryker STIC device is shown in the image below.
Stryker STIC Monitor. Image courtesy of Stryker Corporation, used with permission.
If a commercial device is unavailable, it is possible to assemble a device to measure intracompartment pressure. The device measures the pressure that is necessary to inject a small quantity of fluid. This technique often overestimates low pressures but is generally reliable.
Supplies needed to make a pressure transducer are as follows:
-
One sterile 20-mL Luer-Lok tip syringe (BD Medical Systems)
-
One 4-way stopcock
-
One 18-gauge 1.25-in Angiocath IV catheter (BD Medical Systems)
-
Two 89-cm–long extension tube sets
-
Two 18-gauge needles
-
One bag of sterile normal saline for intravenous infusion
-
One Telfa adhesive dressing pad (Kendall Healthcare Products Co)
-
One blood pressure manometer
A diagram of the device is shown in the image below.
Picture of compartment pressure measuring device for use when commercial devices are unavailable.
Instructions for measuring intracompartmental pressure are as follows [60] :
Clean and prepare the area.
Assemble the 20-mL syringe with the plunger at the 15-mL mark, and connect it to an open end of the 4-way stopcock.
Connect the sterile plastic IV extension tube and an 18-gauge needle on 1 end of the stopcock; connect a second IV extension tube at the opposite end of the stopcock to a blood pressure manometer.
Insert the tip of the 18-gauge needle into the bag of saline, and open the stopcock to allow flow through the needled IV tubing only. Aspirate the saline solution without bubbles into about half the length of the extension tube. Turn the 4-way stopcock to close off this tube so that the saline solution is not lost during transfer of the needle.
Insert the 18-gauge needle into the muscle of the compartment in which the tissue pressure is to be measured.
Turn the stopcock so that the syringe is open to both extension tubes, forming a T connection. This produces a closed system in which the air is free to flow into both extension tubes as the pressure within the system is increased.
Increase the pressure in the system gradually by slowly depressing the plunger of the syringe while watching the saline/air meniscus. The mercury manometer will rise as the pressure within the system rises. When the pressure in this system has just surpassed the tissue pressure surrounding the needle, a small amount of saline solution is injected into the tissue, and the meniscus will be seen to move. When the column moves, stop the pressure on the syringe plunger and read the level of the manometer. The manometer reading at the time the saline column moves is the tissue pressure in mm Hg.
Wick technique of direct compartment-pressure measurement
The wick technique employs strands of a wettable material that extend from the tissue to a fluid-filled catheter that is connected to a pressure transducer. [66]
As long as the wick catheter patency is checked, the wick method is as reliable as continuous-infusion techniques.
Other measurement techniques
Other less-invasive compartment blood flow measurement techniques that have been studied but are not commonly used in clinical practice include the following:
-
Laser Doppler ultrasound
-
Methoxy isobutyl isonitrile enhanced magnetic resonance imaging (MRI)
-
Phosphate-nuclear magnetic resonance (NMR) spectroscopy
-
Thallous chloride-201 (201 Tl ) and technetium-99 (99m Tc) sestamibi, and xenon (Xe) scanning
-
(Click Image to enlarge.) Volar release in the forearm. The upper illustration shows the incision that is used. The lower left picture depicts the relevant incisional anatomy. The lower right picture depicts the cross-sectional anatomy.
-
Surgical anatomy of the volar forearm. Photo courtesy of Dr. Smith, Harborview/UW Medical Center, Department of Orthopaedics, Seattle, Wash.
-
(Click Image to enlarge.) Two-incision anterolateral fasciotomy. Photographs courtesy of DG Smith, MD, Harborview Hospital, Seattle, WA.
-
(Click Image to enlarge.) Two-incision posteromedial fasciotomy. Photographs courtesy of DG Smith, MD, Department of Orthopedics, Harborview Hospital, Seattle, WA.
-
(Click Image to enlarge.) Single-incision fasciotomy. Photographs courtesy of DG Smith, MD, Harborview Hospital, Seattle, WA.
-
Picture of compartment pressure measuring device for use when commercial devices are unavailable.
-
Stryker STIC Monitor. Image courtesy of Stryker Corporation, used with permission.
