Fluorescence-based enhanced reality (FLER) is a technique to evaluate intestinal perfusion based on the elaboration of the Indocyanine Green fluorescence signal. The aim of the study was to assess FLER's performances in evaluating perfusion in an animal model of long-lasting intestinal ischemia.
An ischemic segment was created in 18 small bowel loops in 6 pigs. After 2 h (n = 6), 4 h (n = 6), and 6 h (n = 6), loops were evaluated clinically and by FLER to delineate five regions of interest (ROIs): ischemic zone (ROI 1), presumed viable margins (ROI 2a-2b), and vascularized areas (3a-3b). Capillary lactates were measured to compare clinical vs. FLER assessment. Basal (V 0 ) and maximal (V max) mitochondrial respiration rates were determined according to FLER.
Lactates (mmol/L) at clinically identified resection lines were significantly higher when compared to those identified by FLER (2.43 ± 0.95 vs. 1.55 ± 0.33 p = 0.02) after 4 h of ischemia. Lactates at 2 h at ROI 1 were 5.45 ± 2.44 vs. 1.9 ± 0.6 (2a-2b; p < 0.0001) vs. 1.2 ± 0.3 (3a-3b; p < 0.0001). At 4 h, lactates were 4.36 ± 1.32 (ROI 1) vs. 1.83 ± 0.81 (2a-2b; p < 0.0001) vs. 1.35 ± 0.67 (3a-3b; p < 0.0001). At 6 h, 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). Mean V 0 and V max (pmolO2/second/mg of tissue) were significantly impaired after 4 and 6 h at ROI 1 (V 0 (4h) = 34.83 ± 10.39; V max (4h) = 76.6 ± 29.09; V 0 (6h) = 44.1 ± 12.37 and V max (6h) = 116.1 ± 40.1) when compared to 2a--2b (V 0 (4h) = 67.1 ± 17.47 p = 0.00039; V max (4h) = 146.8 ± 55.47 p = 0.0054; V 0 (6h) = 63.9 ± 28.99 p = 0.03; V max (6h) = 167.2 ± 56.96 p = 0.01). V 0 and V max were significantly higher at 3a-3b.
FLER may identify the future anastomotic site even after repetitive assessments and long-standing bowel ischemia.