Comparison of Near Infrared Tissue Oximetry and Indocyanine Green Angiography in a Porcine Model
Nima Khavanin, MD, Halley Darrach, BA, Kevin Klifto, PharmD, Franca Kraenzlin, MD, Tinglu Han, MD, Pathik Aravind, Hamda Almaazmi, Bashar Safar, MD, Justin M. Sacks, MD.
Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Purpose: Several techniques have gained popularity in their ability to intraoperatively assess tissue perfusion in order to predict and prevent post-operative complications. Indocyanine green angiography (ICG) is among the most widely adopted and studied within the literature; however, its widespread use is limited by the need for costly, specialized equipment, limitations in obtaining repeat measurements, and questions regarding its cost-efficacy in a clinical setting. The Intra.Ox (Vioptix Inc., Fremont, CA) is a novel, hand-held device that utilizes near-infrared spectroscopy without the need for intravenous dye to predict real-time tissue oxygenation. Its lower per-use cost and ability to obtain serial measurements within a single procedure provide benefits over ICG-based angiography, however its efficacy remains to be determined in a clinical setting. This study aims to directly compare measurements of tissue oximetry obtained by the Intra.Ox with the perfusion assessment of the SPY Elite imaging system (Stryker Co., Kalamazoo, MI) in a porcine bowel model.
Methods: Two live minipigs underwent laparotomy and isolation of a 30 cm segment of large bowel under general anesthesia. Standardized oximetry measurements were taken along the segment of bowel immediately before, after, and serially for 30 minutes following transection. A 0.5 mg/kg dose of ICG was then injected intravenously and the SPY Elite system was used to visualize and quantify tissue perfusion. Pearson's correlation coefficients were calculated for the data.
Results: Transected and ligated bowel yielded mean Intra.Ox measurements of 61% oxygenation at the proximal base of the limb and 27.8% at the distal edges. Analysis of the relative ICG fluoresce using the SPY Elite's proprietary software yielded perfusion estimates of 64.8% proximally and 6.8% distally. (Figure, part A) Intra.Ox and SPY Elite measurements demonstrated a Pearson product-moment correlation of 0.940. Repeat measurements at 15 mm intervals along the tissue yielded decreasing Intra.Ox measurements along the length of the flap that correlate to SPY Elite measurements (r = 0.660; Figure, part B).
Conclusions: The Intra.Ox tissue oximeter deleted clinically relevant changes in bowel oxygenation along its length following transection and ligation that appear to correlate well with the changes in perfusion identified by ICG-based angiography. Additional studies are needed to further evaluate the clinical utility and potential cost-efficacy of this novel technology.
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