Ischemia/reperfusion injury in porcine intestine - Viability assessment

Abstract

AIMTo investigate viability assessment of segmental small bowel ischemia/reperfusion in a porcine model.METHODSIn 15 pigs, five or six 30-cm segments of jejunum were simultaneously made ischemic by clamping the mesenteric arteries and veins for 1 to 16 h. Reperfusion was initiated after different intervals of ischemia (1-8 h) and subsequently monitored for 5-15 h. The intestinal segments were regularly photographed and assessed visually and by palpation. Intraluminal lactate and glycerol concentrations were measured by microdialysis, and samples were collected for light microscopy and transmission electron microscopy. The histological changes were described and graded.RESULTSUsing light microscopy, the jejunum was considered as viable until 6 h of ischemia, while with transmission electron microscopy the ischemic muscularis propria was considered viable until 5 h of ischemia. However, following ≥ 1 h of reperfusion, only segments that had been ischemic for ≤ 3 h appeared viable, suggesting a possible upper limit for viability in the porcine mesenteric occlusion model. Although intraluminal microdialysis allowed us to closely monitor the onset and duration of ischemia and the onset of reperfusion, we were unable to find sufficient level of association between tissue viability and metabolic markers to conclude that microdialysis is clinically relevant for viability assessment. Evaluation of color and motility appears to be poor indicators of intestinal viability.CONCLUSIONThree hours of total ischemia of the small bowel followed by reperfusion appears to be the upper limit for viability in this porcine mesenteric ischemia model.

In vivocharacterization of ischemic small intestine using bioimpedance measurements

“…c) The very early change in low frequency phase after 15-30 minutes of bioimpedance was associated with the closing of gap junctions (Strand-Amundsen et al, 2016). d) With transmission electron microscopy we observed the early swelling of muscle cells (Figure 24) during ischemia (Strand-Amundsen et al, 2018a). As the function of the ionic pumps is reduced by ischemia, there is a shift in the ratio between extracellular and intracellular liquid in the muscle cells, where some of the extracellular liquid is being drawn into the cells by osmosis.…”

“…Reperfusion (papers III-V) was initiated by releasing the clamps and verified by observing the return of color in the individual arteries and veins and in the previously ischemic segment. The details of the surgical procedures, anesthesia and monitoring are described in papers I-IV , Strand-Amundsen et al, 2018a, Strand-Amundsen et al, 2017, Strand-Amundsen et al, 2018b). Table 3 shows an overview of the study population in the 3 experiments included in this thesis.…”

“…To assess how these effects influenced the state of the surrounding perfused jejunum, we inspected the control tissue after 12 hours of experiment duration and found only light changes using light microscopy and transmission electron microscopy (Strand-Amundsen et al, 2018a). Microdialysis and histological grading systems did not indicate any changes in the control specimens.…”

“…Repeated measurements ANOVA is less flexible with the structure of random effects compared to LME, requires an equal number of timed effects, and cannot handle missing data or time-dependent covariates. RM ANOVA was also used with the microdialysis data to perform comparisons of the intraluminal lactate and glycerol levels between the control and ischemia/reperfusion segments of jejunum (Strand-Amundsen et al, 2018a).…”

Organ ischemia during partial resuscitative endovascular balloon occlusion of the aorta: Dynamic 4D Computed tomography in swine

“…Several methods for the evaluation of blood flow or ischaemia have been reported. Microdialysis has been used to evaluate ischaemia/reperfusion injury of the intestine 22 . Regional saturation of oxygen can be measured to evaluate tissue oxygenation 23 .…”