162 Chapter 8 Lactate levels Systemic lactate levels ranged from 12 to 30 mmol/L, confirming that none of the pigs experienced systemic ischemia during the experiment. Data collection of the LCL levels missed in one loop at T120, resulting in a total of 167 LCL values collected for analysis. At T0, after ligation of mesenteric arteries, a significant difference in mean LCL levels between wellperfused and ischemic tissue (2.2 ± 0.6 mmol/L and 7.2 ± 1.9 mmol/L, P≤.001) was measured. This difference remained statistically significant over time, with P≤.001 at all timepoints, as can be seen in Figure 4A-D). Between T60 and T120, a significant decrease in LCL levels was seen (10.3 ± 1.6 and 8.2 ± 2.8 mmol/L respectively, P=.015). Changes in mean well-perfused tissue lactate were not significant between T60 and T120 (2.0 ± 0.4 mmol/L versus 2.4 ± 0.9 mmol/L, P=.195). Watershed area mean lactate levels showed an increase over time and were significantly higher than well-perfused LCL levels at all given timepoints. However, these values were significantly lower compared to those in ischemic areas at T60 and T120 (respectively 4.6 ± 2.8 versus 10.3 ± 1.6 and 5.0 ± 2.7 versus 8.2 ± 2.8mmol/L, both P≤.001). Figure 4. Overview of spatial and temporal differences in lactate (mmol/L) per region of interest (ROI). A-C) Violin plots representing lactate levels per Region of Interest (ROI) per timepoint. No measurements were taken at T-1 since ROIs were not yet identified at this moment. Dashed and dotted lines indicate mean values and quartiles, respectively. D) Temporal representation of mean lactate progression with standard deviation. In the first hour after inducing ischemia, the level of lactate rises significantly in the ischemic area. However, a decrease is seen in the second hour. Well-perfused lactate does not change significantly. Levels of significance in all images (P-values): *: ≤0.05; **: ≤0.01; ***: ≤0.001. An overview of all P-values can be found in Supplemental 2.
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