New Isn’t Always Better

NIRS and IMP for OBuzzDiagnosing acute compartment syndrome (ACS) is challenging. The signs and symptoms of ACS are easy to conflate with those of the overall musculoskeletal injury; the treatment, fasciotomy, is not without risks; and the consequences of delaying or missing the diagnosis altogether can be catastrophic. It is for these reasons that the notion of a device that can continuously monitor a wounded extremity for ACS and alert surgeons when intervention should be considered is so appealing. Yet, as the study by Schmidt et al. and the METRC group in the October 3, 2018 JBJS suggests, the ideal and reality are not aligned.

In this prospective blinded study, the authors evaluated the ability of near-infrared spectroscopy (NIRS) sensors and intramuscular pressure (IMP) catheters to monitor the tissue oxygen-saturation and compartment pressures, respectively, of patients who sustained an injury that is associated with the development of compartment syndrome. They found that clinically useful NIRS data was available only about 9% of the time, whereas IMP information was available >85% of the time.  Certain injury characteristics (such as  fractures associated with hematomas) made obtaining data with the NIRS especially difficult.

While these results don’t bode well for NIRS as a reliable ACS monitoring tool, it should be noted that the users of the NIRS system in the study were mostly unaware of when the NIRS system was not collecting clinically useful data in real time. Obviously, you can’t correct a problem if you don’t know it exists, and it is possible the results of the study would have been different if NIRS users were able to troubleshoot the system when data were not being captured. Still, after reading this article, it seems difficult to justify using NIRS to monitor a patient for development of ACS.

New diagnostic tools and techniques are always being developed, and we should remember the results of this study when any “new-fangled” device enters the clinical landscape. A test’s most important feature is its ability to reliably provide clinically useful data to aid in decision-making.  If it cannot do so, it is simply providing distracting ”noise” from which misinterpretations can be made.

Chad A. Krueger, MD
JBJS Deputy Editor for Social Media

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