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Comparing the methods of measuring compartment pressures in acute compartment syndrome
Comparing the Methods of Measuring Compartment Pressures in Acute Compartment Syndrome ANNEMARIE ULIASZ, JAY T. ISHIDA, JASON K. FLEMING, AND LOREN G. YAMAMOTO, MD, MPH, MBA The objectives of this study were to compare the reliability and accuracy of published methods of measuring intramuscular compartment pressures. A muscle compartment model was constructed. Pressure was standardized using a water column exerting pressure on a muscle slab. The following three methods of intracompartmental pressure were used to measure the pressure within the muscle slab of the model: (1) Stryker, (2) manometric IV pump, and (3) Whitesides method. The Stryker and IV pump methods were similarly accurate compared with the “standard pressure.” The Whitesides method was not reliable in measuring a reproducible pressure. The IV pump method is comparable to the Stryker instrument in terms of accuracy and ease of use. If a Stryker instrument is unavailable, the IV pump method can serve as a suitable and satisfactory alternative. (Am J Emerg Med 2003;21:143-145. Copyright 2003, Elsevier Science (USA). All rights reserved.)
Compartment syndrome is a potentially limb- and lifethreatening condition in which pressure elevation of an enclosed compartment results in ischemia as a result of venous outflow obstruction and eventual tissue infarction. Compartment syndrome may be caused by external constriction/compression or intracompartmental swelling or hemorrhage. If left untreated or treatment is delayed, compartment syndrome can lead to ischemia and necrosis, in turn causing muscular and neurologic damage. It is imperative to identify and diagnose a compartment syndrome condition in a timely fashion so surgical intervention can prevent irreversible neuromuscular injury. Measurement of the intracompartmental pressure is required to identify a compartment syndrome. The intracompartmental pressure of a normal muscle compartment is less than 10 mmHg.1 As intracompartmental pressure rises, venous outflow, and hence capillary blood flow, is impeded
From the Department of Pediatrics, University of Hawaii John A. Burns School of Medicine, and the Emergency Department, Kapiolani Medical Center for Women and Children, Honolulu, Hawaii. Manuscript received February 9, 2002, accepted May 7, 2002. Abstract presented at the Scientific Research Forum of the American College of Emergency Physicians Annual Meeting, Chicago, IL, October 2001; the National Conference and Exhibition of the American Academy of Pediatrics, San Francisco, CA, October 2001; and the Annual Meeting of the American Academy of Orthopedic Surgeons, Dallas, TX, February 2002. Address reprint requests to Loren G. Yamamoto, MD, MPH, MBA, Professor of Pediatrics, University of Hawaii John A. Burns School of Medicine, 1319 Punahou Street, #733, Honolulu, HI 96826. E-mail: [email protected] Key Words: Compartment syndrome, compartment pressure measurement. Copyright 2003, Elsevier Science (USA). All rights reserved. 0735-6757/03/2102-0012$30.00/0 doi:10.1053/ajem.2003.50035
and eventually ceases. At some threshold, the intracompartmental pressure increases and compromises intracompartmental perfusion, eventually resulting in infarction. This intracompartmental pressure threshold is controversial and beyond the scope of this report, but most reports indicate that it is somewhere between 30 mmHg and 45 mmHg.1-4 Fasciotomy is required when intracompartmental pressures exceed this threshold. Because the speed of diagnosis and treatment determines the prognosis of this condition, rapid and accurate intracompartmental pressure measurement is critical. The Stryker Quick Pressure Monitor instrument (Stryker Surgical, Kalamazoo, MI) is a device specifically designed to measure intracompartmental pressure. Because it is expensive, not all medical facilities may have access to this device. Alternative intracompartmental pressure measurement methods to the Stryker device include the IV pump method5 and the Whitesides technique.6-8 The purpose of this study is to assess and compare the accuracy of several different methods of intracompartmental pressure measurement using a model. METHODS A model of a muscle compartment was developed consisting of a vertical cylindrical column of water overlying a slab of beef muscle (see Fig 1). The height of the water column determined the “standard pressure,” which is the pressure exerted on the muscle slab (in centimeters of water). This model was used to assess the accuracy of various instruments in the measurement of pressure within the muscle slab. Pressure readings from the three intracompartmental pressure measuring methods were compared with the “standard pressure” from the water column height. Pressure in centimeters of water was converted to mmHg (Torr) by multiplying the pressure in centimeters of water by 0.7333. “Standard pressures” ranging from 30 to 90 cm H2O (22-66 mmHg) were achieved by varying the height of the water column. The three devices were used to measure pressure within the muscle slab at each “standard pressure.” Pressure measurements using the three methods were repeated three times at each “standard pressure” level (22, 33, 44, 55, and 66 mmHg). This procedure was run on 3 separate days using a different muscle slab so that 9 measurements for each method were performed at each “standard pressure” level (ie, 45 measurements for each device). Measurements using the Stryker instrument were performed following the instructions provided by Stryker as follows: (1) Fill the Stryker instrument with normal saline; 143
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AMERICAN JOURNAL OF EMERGENCY MEDICINE ■ Volume 21, Number 2 ■ March 2003
RESULTS
FIGURE 1. Muscular compartment model using a water column as the pressure standard.
(2) zero the Stryker instrument; (3) insert the needle into the area of measurement; (4) inject 0.3 cc normal saline; and (5) read the pressure measurement. Measurements using the IV pump were performed using an IV pump with pressure sensing capability (Alaris Medical Systems #7130B7, San Diego, CA) similar to the method described by Uppal5: (1) Set the IV pump to manometry mode; (2) zero the IV pump; (3) insert the needle into the tissue being measured; (4) infuse 0.3 cc normal saline at a slow infusion rate; and (5) read the pressure measurement. Measurements using the Whitesides method were performed according to the procedure describing it6-8: (1) Connect IV tubing to the front and rear ports of the three-way stopcock; (2) connect a 10-ml syringe with the plunger at the 3-mL mark to the upper port; (3) connect the needle to the end of the IV extension tubing and turn the stopcock so the other IV extension tubing connected to a mercury manometer is in the “off” position; (4) place the needle into saline and use the syringe to draw up the saline through the needle through the tubing attached to the needle so that saline fills the tubing from the tip of the needle to the halfway point in the tubing, the other half of the tubing containing only air; (5) insert the needle into the tissue being measured; (6) turn the stopcock so that all three ports are in the “open” position; (7) depress the plunger of the syringe slowly, causing a rise in pressure within the system; the mercury column will rise until pressure within the system is equal to pressure within the compartment; and (8) the compartment pressure is the reading on the manometer at the time the saline first begins to move and when the meniscus of the saline is flat (not convex or concave).
Both the Stryker and IV pump methods were similar in ease of use. We could not get a consistent pressure reading using the Whitesides technique. The means, standard deviations, and range for the value pressure measurements within the muscle slab are summarized in Table 1. Both methods approximated the “standard pressure.” Based on the range of values obtained, both methods require multiple measurements to approximate the true “standard pressure” within the muscle slab. The standard deviations and ranges (difference between the minimum value and maximum value) for the IV pump were smaller than that of the Stryker. The readings for the IV pump and Stryker are depicted in Figure 2. The scatter of the measurements is visibly narrower for the IV pump compared with the Stryker. We do not understand why the Whitesides technique did not work well. We noticed that the air/fluid level in the tubing would move at pressure levels that would differ by more than 10 to 20 mmHg despite no change in the “standard pressure.” Examining the shape of the meniscus did not help either. The pressure readings would not hold steady for us to record a single number reading because the manometer would fluctuate by more than 10 to 20 mmHg. A mercury column manometer was used in our model. Others have used an electronic manometer, which uses a slightly different technique, but in theory, the pressure readings should be identical.
FIGURE 2.
Scattergram of pressure measurements.
ULIASZ ET AL ■ COMPARTMENT SYNDROME PRESSURE MEASUREMENT
DISCUSSION The diagnosis of acute compartment syndrome is highly important to rule in and rule out compartment syndrome. Immediate surgical intervention is required if the condition is present. Clinical risk estimation is not good enough. Diagnostic certainty must be high if the patient is to be subjected to an invasive surgical procedure. Accurate measurement of the intracompartmental pressure is the only way to determine with certainty if an acute compartment syndrome is present. Both the Stryker and IV pump methods were accurate in comparison to the “standard pressure” exerted by the water column. The Whitesides method, however, did not yield accurate or consistent results, and therefore we were unable to assess its accuracy. Additionally, the Whitesides method is more difficult to set up. Mercury manometers are not readily available any more. Electronic manometers are routinely used in the ICU (not the case in the ED), which adds additional complexity to this method. This shows that the IV pump method is comparable to the Stryker instrument in terms of accuracy and ease of use. If a Stryker instrument is unavailable, the IV pump method may serve as a suitable and satisfactory alternative. Even if a Stryker instrument is available, the IV pump method could be used as a double check to confirm that both measurement methods are in agreement. Certainty is highly desirable here because failing to identify a compartment syndrome will result in severe complications. The Stryker instrument is expensive ($1575, plus $66 disposable unit per use). It is likely that at least some, and possibly many, EDs do not have the Stryker instrument available. Additionally, although the Stryker instrument is available in our ED, there have been times when our stock of the disposable syringe units were depleted, and thus we would not be able to use the Stryker instrument until the disposable syringe units were restocked. The IV pump method can serve as a useful back-up. Such IV pumps are expensive as well, but they are readily available in all hospitals and already purchased for IV infusion monitoring, compared with a Stryker instrument which has only a single purpose and may not be available. A previous study using an older model of manometric IV pumps (the IVAC) found the pressure reading from an IV pump similar to the Stryker. In this case the Stryker was used as the gold standard. Our study differs from this
145
because our model uses an independent “standard pressure” to which the IV pump and Stryker measurements are compared. Our results indicate that both methods have useful clinical accuracy, but the variance of the IV pump measurements were narrower than that of the Stryker. Our model indicates that as long as several measurements are taken to obtain a mean estimate of the intracompartmental pressure, the mean should closely correlate to the “standard pressure” using both methods. Although most modern IV pumps have manometric capabilities to more carefully monitor the status of an IV infusion, only some IV pumps have the capability of giving an actual pressure reading. Some less costly IV infusion pumps only display a pressure range rather than a single pressure measurement value. Unless the ranges are sufficiently narrow, such IV infusion pumps would not be useful to measure the intracompartmental pressure reliably. We found the IV pump method to be easy and intuitive. The pressure displays zero when the needle is outside the muscle, then it quickly approximates the “standard pressure” once it was inserted into the muscle slab. In summary, the Stryker instrument and the IV pump method were both found to be fairly accurate and reliable methods of measuring the intramuscular pressure of our model. REFERENCES 1. Perron AD, Brady WJ, Keats TE: Orthopedic pitfalls in the ED: acute compartment syndrome. Am J Emerg Med 2001;19:413-6 2. Azar FM, Pickering RM: Traumatic disorders, in Canale ST, Daugherty K, Jones L (eds): Campbell’s Operative Procedures (ed 9). St. Louis: Mosby-Year Book, 1998, pp. 1405-11 3. Jobe MT: Compartment syndromes and Volkmann contracture. In: Canale ST, Daugherty K, Jones L (eds). Campbell’s Operative Orthopaedics, 9th ed. St. Louis: Mosby-Year Book, 1998, pp. 3661-74 4. Mars M, Hadley GP: Raised intracompartmental pressure and compartment syndromes. Injury 1998;29:403-11 5. Uppal GS, Smith GC, Sherk HH, Mooar P: Accurate compartment pressure measurement using the Intervenous Alarm Control (IVAC) Pump: report of a technique. J Orthop Trauma 1992;6:87-9 6. Whitesides TE Jr, Haney TC, Harada H, et al: A simple method for tissue pressure determination. Arch Surg 1975;110:1311-3 7. Whitesides TE Jr, Haney TC, Morimoto K, et al: Tissue pressure measurements as a determinant for the need of fasciotomy. Clin Orthop 1975;113:43-51 8. Freedman SH, King BR: Approach to fractures with neurovascular compromise. In: Henretig FM, King C (eds). Textbook of Pediatric Emergency Procedures. Baltimore: Williams & Wilkins, 1997, pp. 1113-4
Compartment syndrome is a potentially limb- and lifethreatening condition in which pressure elevation of an enclosed compartment results in ischemia as a result of venous outflow obstruction and eventual tissue infarction. Compartment syndrome may be caused by external constriction/compression or intracompartmental swelling or hemorrhage. If left untreated or treatment is delayed, compartment syndrome can lead to ischemia and necrosis, in turn causing muscular and neurologic damage. It is imperative to identify and diagnose a compartment syndrome condition in a timely fashion so surgical intervention can prevent irreversible neuromuscular injury. Measurement of the intracompartmental pressure is required to identify a compartment syndrome. The intracompartmental pressure of a normal muscle compartment is less than 10 mmHg.1 As intracompartmental pressure rises, venous outflow, and hence capillary blood flow, is impeded
From the Department of Pediatrics, University of Hawaii John A. Burns School of Medicine, and the Emergency Department, Kapiolani Medical Center for Women and Children, Honolulu, Hawaii. Manuscript received February 9, 2002, accepted May 7, 2002. Abstract presented at the Scientific Research Forum of the American College of Emergency Physicians Annual Meeting, Chicago, IL, October 2001; the National Conference and Exhibition of the American Academy of Pediatrics, San Francisco, CA, October 2001; and the Annual Meeting of the American Academy of Orthopedic Surgeons, Dallas, TX, February 2002. Address reprint requests to Loren G. Yamamoto, MD, MPH, MBA, Professor of Pediatrics, University of Hawaii John A. Burns School of Medicine, 1319 Punahou Street, #733, Honolulu, HI 96826. E-mail: [email protected] Key Words: Compartment syndrome, compartment pressure measurement. Copyright 2003, Elsevier Science (USA). All rights reserved. 0735-6757/03/2102-0012$30.00/0 doi:10.1053/ajem.2003.50035
and eventually ceases. At some threshold, the intracompartmental pressure increases and compromises intracompartmental perfusion, eventually resulting in infarction. This intracompartmental pressure threshold is controversial and beyond the scope of this report, but most reports indicate that it is somewhere between 30 mmHg and 45 mmHg.1-4 Fasciotomy is required when intracompartmental pressures exceed this threshold. Because the speed of diagnosis and treatment determines the prognosis of this condition, rapid and accurate intracompartmental pressure measurement is critical. The Stryker Quick Pressure Monitor instrument (Stryker Surgical, Kalamazoo, MI) is a device specifically designed to measure intracompartmental pressure. Because it is expensive, not all medical facilities may have access to this device. Alternative intracompartmental pressure measurement methods to the Stryker device include the IV pump method5 and the Whitesides technique.6-8 The purpose of this study is to assess and compare the accuracy of several different methods of intracompartmental pressure measurement using a model. METHODS A model of a muscle compartment was developed consisting of a vertical cylindrical column of water overlying a slab of beef muscle (see Fig 1). The height of the water column determined the “standard pressure,” which is the pressure exerted on the muscle slab (in centimeters of water). This model was used to assess the accuracy of various instruments in the measurement of pressure within the muscle slab. Pressure readings from the three intracompartmental pressure measuring methods were compared with the “standard pressure” from the water column height. Pressure in centimeters of water was converted to mmHg (Torr) by multiplying the pressure in centimeters of water by 0.7333. “Standard pressures” ranging from 30 to 90 cm H2O (22-66 mmHg) were achieved by varying the height of the water column. The three devices were used to measure pressure within the muscle slab at each “standard pressure.” Pressure measurements using the three methods were repeated three times at each “standard pressure” level (22, 33, 44, 55, and 66 mmHg). This procedure was run on 3 separate days using a different muscle slab so that 9 measurements for each method were performed at each “standard pressure” level (ie, 45 measurements for each device). Measurements using the Stryker instrument were performed following the instructions provided by Stryker as follows: (1) Fill the Stryker instrument with normal saline; 143
144
AMERICAN JOURNAL OF EMERGENCY MEDICINE ■ Volume 21, Number 2 ■ March 2003
RESULTS
FIGURE 1. Muscular compartment model using a water column as the pressure standard.
(2) zero the Stryker instrument; (3) insert the needle into the area of measurement; (4) inject 0.3 cc normal saline; and (5) read the pressure measurement. Measurements using the IV pump were performed using an IV pump with pressure sensing capability (Alaris Medical Systems #7130B7, San Diego, CA) similar to the method described by Uppal5: (1) Set the IV pump to manometry mode; (2) zero the IV pump; (3) insert the needle into the tissue being measured; (4) infuse 0.3 cc normal saline at a slow infusion rate; and (5) read the pressure measurement. Measurements using the Whitesides method were performed according to the procedure describing it6-8: (1) Connect IV tubing to the front and rear ports of the three-way stopcock; (2) connect a 10-ml syringe with the plunger at the 3-mL mark to the upper port; (3) connect the needle to the end of the IV extension tubing and turn the stopcock so the other IV extension tubing connected to a mercury manometer is in the “off” position; (4) place the needle into saline and use the syringe to draw up the saline through the needle through the tubing attached to the needle so that saline fills the tubing from the tip of the needle to the halfway point in the tubing, the other half of the tubing containing only air; (5) insert the needle into the tissue being measured; (6) turn the stopcock so that all three ports are in the “open” position; (7) depress the plunger of the syringe slowly, causing a rise in pressure within the system; the mercury column will rise until pressure within the system is equal to pressure within the compartment; and (8) the compartment pressure is the reading on the manometer at the time the saline first begins to move and when the meniscus of the saline is flat (not convex or concave).
Both the Stryker and IV pump methods were similar in ease of use. We could not get a consistent pressure reading using the Whitesides technique. The means, standard deviations, and range for the value pressure measurements within the muscle slab are summarized in Table 1. Both methods approximated the “standard pressure.” Based on the range of values obtained, both methods require multiple measurements to approximate the true “standard pressure” within the muscle slab. The standard deviations and ranges (difference between the minimum value and maximum value) for the IV pump were smaller than that of the Stryker. The readings for the IV pump and Stryker are depicted in Figure 2. The scatter of the measurements is visibly narrower for the IV pump compared with the Stryker. We do not understand why the Whitesides technique did not work well. We noticed that the air/fluid level in the tubing would move at pressure levels that would differ by more than 10 to 20 mmHg despite no change in the “standard pressure.” Examining the shape of the meniscus did not help either. The pressure readings would not hold steady for us to record a single number reading because the manometer would fluctuate by more than 10 to 20 mmHg. A mercury column manometer was used in our model. Others have used an electronic manometer, which uses a slightly different technique, but in theory, the pressure readings should be identical.
FIGURE 2.
Scattergram of pressure measurements.
ULIASZ ET AL ■ COMPARTMENT SYNDROME PRESSURE MEASUREMENT
DISCUSSION The diagnosis of acute compartment syndrome is highly important to rule in and rule out compartment syndrome. Immediate surgical intervention is required if the condition is present. Clinical risk estimation is not good enough. Diagnostic certainty must be high if the patient is to be subjected to an invasive surgical procedure. Accurate measurement of the intracompartmental pressure is the only way to determine with certainty if an acute compartment syndrome is present. Both the Stryker and IV pump methods were accurate in comparison to the “standard pressure” exerted by the water column. The Whitesides method, however, did not yield accurate or consistent results, and therefore we were unable to assess its accuracy. Additionally, the Whitesides method is more difficult to set up. Mercury manometers are not readily available any more. Electronic manometers are routinely used in the ICU (not the case in the ED), which adds additional complexity to this method. This shows that the IV pump method is comparable to the Stryker instrument in terms of accuracy and ease of use. If a Stryker instrument is unavailable, the IV pump method may serve as a suitable and satisfactory alternative. Even if a Stryker instrument is available, the IV pump method could be used as a double check to confirm that both measurement methods are in agreement. Certainty is highly desirable here because failing to identify a compartment syndrome will result in severe complications. The Stryker instrument is expensive ($1575, plus $66 disposable unit per use). It is likely that at least some, and possibly many, EDs do not have the Stryker instrument available. Additionally, although the Stryker instrument is available in our ED, there have been times when our stock of the disposable syringe units were depleted, and thus we would not be able to use the Stryker instrument until the disposable syringe units were restocked. The IV pump method can serve as a useful back-up. Such IV pumps are expensive as well, but they are readily available in all hospitals and already purchased for IV infusion monitoring, compared with a Stryker instrument which has only a single purpose and may not be available. A previous study using an older model of manometric IV pumps (the IVAC) found the pressure reading from an IV pump similar to the Stryker. In this case the Stryker was used as the gold standard. Our study differs from this
145
because our model uses an independent “standard pressure” to which the IV pump and Stryker measurements are compared. Our results indicate that both methods have useful clinical accuracy, but the variance of the IV pump measurements were narrower than that of the Stryker. Our model indicates that as long as several measurements are taken to obtain a mean estimate of the intracompartmental pressure, the mean should closely correlate to the “standard pressure” using both methods. Although most modern IV pumps have manometric capabilities to more carefully monitor the status of an IV infusion, only some IV pumps have the capability of giving an actual pressure reading. Some less costly IV infusion pumps only display a pressure range rather than a single pressure measurement value. Unless the ranges are sufficiently narrow, such IV infusion pumps would not be useful to measure the intracompartmental pressure reliably. We found the IV pump method to be easy and intuitive. The pressure displays zero when the needle is outside the muscle, then it quickly approximates the “standard pressure” once it was inserted into the muscle slab. In summary, the Stryker instrument and the IV pump method were both found to be fairly accurate and reliable methods of measuring the intramuscular pressure of our model. REFERENCES 1. Perron AD, Brady WJ, Keats TE: Orthopedic pitfalls in the ED: acute compartment syndrome. Am J Emerg Med 2001;19:413-6 2. Azar FM, Pickering RM: Traumatic disorders, in Canale ST, Daugherty K, Jones L (eds): Campbell’s Operative Procedures (ed 9). St. Louis: Mosby-Year Book, 1998, pp. 1405-11 3. Jobe MT: Compartment syndromes and Volkmann contracture. In: Canale ST, Daugherty K, Jones L (eds). Campbell’s Operative Orthopaedics, 9th ed. St. Louis: Mosby-Year Book, 1998, pp. 3661-74 4. Mars M, Hadley GP: Raised intracompartmental pressure and compartment syndromes. Injury 1998;29:403-11 5. Uppal GS, Smith GC, Sherk HH, Mooar P: Accurate compartment pressure measurement using the Intervenous Alarm Control (IVAC) Pump: report of a technique. J Orthop Trauma 1992;6:87-9 6. Whitesides TE Jr, Haney TC, Harada H, et al: A simple method for tissue pressure determination. Arch Surg 1975;110:1311-3 7. Whitesides TE Jr, Haney TC, Morimoto K, et al: Tissue pressure measurements as a determinant for the need of fasciotomy. Clin Orthop 1975;113:43-51 8. Freedman SH, King BR: Approach to fractures with neurovascular compromise. In: Henretig FM, King C (eds). Textbook of Pediatric Emergency Procedures. Baltimore: Williams & Wilkins, 1997, pp. 1113-4