Real-time Navigation by Fluorescence-based Enhanced Reality for Precise Estimation of Future Anastomotic Site in Digestive Surgery

Michele Diana, MD, Pierre Diemunsch, MD, PhD, Yoshihiro Nagao, MD, Peter Halvax, MD, Anne-Laure Charles, MD, PhD, Bernard Geny, MD, PhD, Bernard Dallemagne, MD, Vincent Agnus, PhD, Luc Soler, PhD, Nicolas Demartines, MD, FACS, FRCS, Didier Mutter, MD, PhD, FACS, Jacques Marescaux, MD, FACS, HON, FRCS, HON, FJSES. 1) IRCAD/IHU, Digestive and Endocrine Surgery, University of Strasbourg 2) Anaesthesiology, University of Strasbourg, 3) Phisiology and Oxydative Stress Laboratory, University of Strasbourg 4) Visceral Surgery, University Hospital Lausanne, Switzerland.

Fluorescence-based Enhanced Reality (FLER) is a novel technique to evaluate intestinal perfusion based on the use of a Near Infra-Red endoscope (D-light P, Karl Storz®) to detect the Indocyanine Green (ICG) fluorescence signal. A digital perfusion cartography is computed from the time-to-peak of the fluorescent signal and is superimposed to the intraoperative laparoscopic image using VR-RENDER® software.The aim of this study was to assess the ability of the FLER to identify the future resection lines in a reiterate model of intestinal ischemia.

Materials and Methods
An ischemic segment was created in 18 small bowel loops in 6 pigs (3 loops/pig) by sealing 3-4 mesenteric vessels. After 2hours (n=6), 4hours (n=6) and 6hours (n=6), the ischemic segments were evaluated by clinical assessment (by a second surgeon blinded to the extent of the mesenteric window) and by FLER, to determine presumed viable margins. Five regions of interest (ROIs) were identified: ischemic (ROI 1), presumed viable margins (ROI 2a&2b), and vascular areas (3a&3b). Presumed viable margins as assessed by clinical evaluation (2aCLINIC+2bCLINIC), were marked with a clip, while those identified under FLER guidance (2aFLER+2bFLER) were outlined with a surgical marker. A laparotomy was performed and capillary blood samples were obtained by puncturing the bowel serosa at the ROIs and lactates were measured using the handheld EDGE® lactate analyzer (Apexbio, Taiwan). A surgical biopsy sampled at the ROIs as evaluated by FLER, was placed in a 2mL water-jacketed oxygraphic cell (Oxygraph-2k©, OROBOROS instruments®, Innsbrück, Austria). After determination of basal oxygen consumption (V0), the mitochondrial respiration rates were measured at 37°C in the presence of a saturating amount of ADP as phosphate acceptor (VADP) to evaluate complexes I, III, and IV. Complex II was then stimulated with succinate to evaluate VMAX of mitochondrial respiration.

Mean capillary lactate levels at 2h were 5.45±2.44 vs. 1.9±0.6 vs. 1.2±0.3 mmol/L at ROI 1 vs. 2a&2b (p<0.0001) vs. 3a&3b (p<0.0001) respectively. At 4h, lactates were 4.36±1.32 vs. 1.83±0.81 vs. 1.35±0.67 mmol/L at ROI 1 vs. 2a&2b (p<0.0001) vs. 3a&3b (p<0.0001). At 6h, lactates were 4.16±2.55 vs. 1.8±1.2 vs. 1.45±0.83 at ROI 1 vs. 2a-2b (p=0.013) vs. 3a-3b (p=0.0035). Lactate levels at presumed viable margins assessed by clinical evaluation (2aCLINIC+2bCLINIC) were statistically significantly higher when compared to those at 2aFLER+2bFLER (2.43±0.95 mmol/L vs. 1.55±0.33 p=0.02) after 4h of ischemia. Mean basal mitochondrial respiratory rate expressed in pmolO2/second/mg of dry tissue (V0 and VMAX) were significantly impaired after 4h and 6h of ischemia at ROI1 (V04h=42.7±25.81; VMAX4h =76.6±29.09; V06h=44.1±12.37 and VMAX6h=116.1±40.1) when compared to 2a&2b (V04h=67.1±17.47 p=0.0003; VMAX4h=146.8±55.47 p=0.0054; V06h=63.9±28.99 p=0.03; VMAX6h=167.2±56.96 p=0.01). V0 and VMAX were statistically significantly higher at the vascular areas at all-time points. No differences between ROIs 2a&2b and 3a&3b were found for lactate levels and mitochondria respiratory rate.

Fluorescence-based Enhanced Reality allows for real time determination of the optimal anastomotic site and can detect the boundary between the ischemic and the vascularized zones even after repetitive assessments with a better performance when compared to clinical evaluation.

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