gms | German Medical Science

Background: Intestinal ischemia as life-threatening event must be rapidly diagnosed and treated, but still intraoperative evaluation of bowel perfusion remains subjective and treatment strategies depend on the surgeon´s personal experience. Especially detection of resection margins is important to improve patients’ outcome.

Aim of the present experimental study was to evaluate fluorescent-imaging (FI) using indocyanine green (ICG) for visual and quantitative assessment of bowel perfusion during and after ischemia in a porcine model.

Materials and methods: 16 pigs of either sex (54,2±2,9kg) underwent occlusion of upper mesenteric-side branch-artery occlusion for 3hours (group I, n=8), and 6hours (group II, n=8) via median laparotomy, followed by 60minutes of reperfusion. 3 areas were defined: ischemic bowel (D1), transitional zone (D2), and non-ischemic bowel (D3).

Hemodynamic parameters, transit-time flood flow (TTFM) of the mesenteric artery and partial pressure of tissue oxygen (tpO₂) in D1 and D3 were continuously assessed.

FI was performed during baseline (T0), during occlusion of the mesenteric-sidebranch-artery (T1), during release occlusion (T2) and after 60 minutes reperfusion (T4).

Results: Study protocol including FI could successfully be performed during stable hemodynamics in all pigs.

TTFM flow was equal in both groups during T0 (69,7± 16,5 ml/min), decreased to 0±0ml/min during complete occlusion, and increased after reperfusion to highest values at T4 (group I: 60,7 ± 48,4 ml/min, group II: 97,1 ± 31,0 ml/min; n.s.). Increase of flow was significantly different at 15 and 30 minutes after reperfusion (p<0,05).

TpO₂ decreased significantly in all groups during ischemia to increase again at reperfusion. Increase of tpO₂ was higher in group 1 as compared to group 2 (group 1: 33,1±, group 2: 14,1±x, n.s.) but did never return to baseline values (T0:36,7±2,7 vs. T4: group I: 24,3±, group II: 14,8 ± 10,3; n.s.).

FI was assessed as baseline adjusted FI-Ratio. During occlusion FI-Ratio confirmed loss of perfusion in D1 (group1: 0,14±0,09; group 2: 0,08±0,05), showed decreased perfusion during D2 (group1: 0,55±0,38; group 2: 0,54±0,52), and increased perfusion in D3 (group1:1,87±1,36; group 1,25±0,71). After reperfusion the FI-Ratio in D1 increased in group 2 (1,83±1,18) indicating capillary leakage, while FI-Ratio was almost comparable to baseline in group 1 (0,99±0,82) indicating reversible perfusion deficit. After Reperfusion D2 showed increased fluorescent intensity in both groups as compared to baseline values (group 1: 2,02±1,95 vs. group 2: 1,49±0,89);D3 showed comparable values to baseline at the different measurements (group 1:0,92±0,5 vs. group 2: 1,12±0,78).

Conclusion: Visual and quantitative assessment of bowel perfusion is feasible in the experimental setting. Also differences in between the different perfusion zones can be evaluated by FI. 6 h ischemia with increased FI Ratio indicates capillary leakage, while fluorescence intensity comparable to baseline values as measured after 3 h ischemia indicates complete reversible perfusion deficiency. This might be promising tool for intraoperative assessment of bowels perfusion in the future.