Bilateral near-infrared spectroscopy for detecting traumatic vascular injury

Background: Extremity wounds account for most battlefield injuries. Clinical examination may be unreliable by medics or first responders, and continuous assessment by experienced practitioners may not be possible on the frontline or during transport. Near-infrared spectroscopy (NIRS) provides continuous, noninvasive monitoring of tissue oxygen saturation (StO ₂), but its use is limited by inter-patient and intra-patient variability. We tested the hypothesis that bilateral NIRS partially addresses the variability problem and can reliably identify vascular injury after extremity trauma. Materials and methods: This prospective study consisted of 30 subjects: 20 trauma patients with extremity injury and 10 healthy volunteers. Bilateral StO₂ tissue sensors were placed on the thenar eminence or medial plantar surface. Injured and non-injured extremities within the same patient (ΔStO₂) were compared using Wilcoxon signed ranks test. Receiver operating characteristic curves were generated and areas under the curve (AUCs) were calculated for ΔStO₂ of 6, 10, and 15. Values are expressed as median (interquartile range). Results: Trauma patients were age 31 y (23 y), 85% male, with injury severity score of 9 (5). There were seven arterial and three venous injuries. Most involved the lower extremity (n = 16; 80%) and resulted from a penetrating mechanism (n = 14; 70%). ΔStO ₂ between limbs was 20.4 (10.4) versus 2.4 (3.0) (P < 0.001) for all patients with vascular injury versus patients and volunteers with no vascular injury. ΔStO₂ reliably identified any vascular injury (AUC, 0.975; P < 0.001), whereas pulse examination alone or in combination with Doppler exam could detect only arterial injury. A ΔStO₂ of 6 had the greatest sensitivity and specificity (AUC, 0.900; P < 0.001). Conclusions: Continuous monitoring of bilateral limbs with NIRS detects changes in perfusion resulting from arterial or venous injury and may offer advantages over serial manual measurements of pulses or Doppler signals. This technique may be most relevant in military and disaster scenarios or during transport, in which the ability to monitor limb perfusion is difficult or experienced clinical judgment is unavailable.