Near-infrared spectroscopy versos compartment pressure for the diagnosis of lower extremity compartmental syndrome using electromyography-determined measurements of neuromuscular function

Background: Compartmental syndrome (CS) is difficult to diagnose in intensi ve care unit patients. Compartment perfusion pressure (CPP) is an invasive, indirect measure of ischemia, Near-infrared spectroscopy is noninvasive, a nd directly measures ischemia by transmitting light through tissues at wave lengths that react with hemoglobin to provide percent tissue oxygen saturat ion (Sto(2)), Animal studies demonstrate that Sto(2) is superior to CPP for detecting CS, However, there are no studies in humans comparing Sto(2) wit h CPP, We hypothesized that Sto(2) can reliably detect CS, and is superior to CPP, Methods: CS was induced in 15 human volunteers using a standard calf compre ssion model. At 30-minute intervals, compression was increased to reduce St o(2) from baseline (86% +/- 4%) to 60%, 40%, 20%, and < 10%, with simultane ous recording of CPP, Outcome variables included deep peroneal nerve conduc tion assessed by electromyography, cutaneous peroneal nerve sensitivity usi ng Semmes-Weinstein monofilaments, and pain (visual analog scale). Results: Both Sto(2) and CPP significantly correlated with all ischemia out come variables (p < 0.001), Receiver operating characteristic curves of dee p peroneal nerve conduction demonstrated that Sto(2) had higher sensitivity than CPP for detecting > 50% block. For example, when specificity was 83% for Sto(2) and 84% for CPP, sensitivity was 85% versus 56%, respectively (p = 0.02), When specificity for both was 72%, sensitivity was 94% for Sto(2) versus 76% for CPP (p = 0.04). Conslusion: In intensive care unit patients who cannot alert physicians to symptoms, near-infrared spectroscopy may help clinicians to avoid delayed o r unnecessary prophylactic fasciotomy, and provides the benefits of a conti nuous, noninvasive monitoring technique.