Morgan R Barron, MD, John P Kuckelman, DO, John M McClellan, MD, Michael J Derickson, MD, Cody J Phillips, DO, Matthew J Eckert, MD, Matthew J Martin, MD. Madigan Army Medical Center
OBJECTIVES: Over the past decade there has been a resurgence of tourniquet (TQ) use in civilian and military settings. Several key challenges include assessment of limb perfusion and adequacy of TQ placement, particularly in the austere or pre-hospital environments. We investigated the utility of a novel smartphone-based forward-looking infrared (FLIR) system.
METHODS: A commercially available device (FLIR One, FLIR Systems, Inc.) that converts standard smartphones to a highly sensitive infrared thermal imager was utilized. Ten swine underwent tourniquet placement with no associated hemorrhage (NH) or with 40% hemorrhage (H). Static images were taken at 0, 5, 10, 20, and 30-minutes in 3 experiments. Experiment 1 simulated proper TQ application and experiment 2 had one TQ inadequately tightened. Experiment 3 simulated blackout combat conditions. FLIR temperatures, images, hemodynamics, and labs were collected. FLIR images were also presented to blinded observers who scored limb perfusion and adequacy of TQ placement.
RESULTS: The mean core temperature and MAP was 38.1°C and 62 mmHg in NH animals versus 38.2°C and 47 mmHg in H animals. H animals were more hypotensive (p=0.01), anemic (HCT 14 vs 20, p=0.02), tachycardic (126 bpm vs 101, p=0.04), and vasodilated (SVR 641 vs 1004, p=0.008), than NH animals. The FLIR temperature reading decreased significantly following proper TQ placement in all animals, with no difference between H and NH groups (ΔTemp 9.8±4°C vs 10.8±2°C; p=0.7). Qualitative FLIR image analysis showed clearly visible perfusion differences in all animals between baseline, adequate TQ, and inadequate TQ in both H and NH groups. The vast majority of blinded evaluators (n=29) correctly identified adequate and inadequate TQ placement at the 5-minute (98% correct) and 10-minute (99% correct) time points. Images in blackout combat-simulation conditions showed no adverse impact on thermal measurements, thermal changes with TQ placement, or in the ability to accurately characterize perfusion and TQ adequacy.
CONCLUSION: A simple handheld smartphone-based FLIR device demonstrated a high degree of accuracy, reliability, and ease of use for assessing limb perfusion. FLIR also allowed for rapid and reliable identification of adequate TQ placement that was not affected by co-existing major hemorrhage or blackout conditions.
Presented at the SAGES 2017 Annual Meeting in Houston, TX.
Abstract ID: 80958
Program Number: MSS20
Presentation Session: Full-Day Military Surgical Symposium – Trauma/Critical Care Presentations
Presentation Type: MSSPodium