Characterization of Renal Ischemia Using DLP (R) Hyperspectral Imaging: A Pilot Study Comparing Artery-Only Occlusion Versus Artery and Vein Occlusion

Background and Purpose: Renal artery-only (AO) occlusion, as opposed to artery and vein (AV) occlusion, has demonstrated some benefit in reducing renal insufficiency during warm ischemia. In this pilot study, we used digital light projection hyperspectral imaging (HSI) to construct a real time'' tissue oxygenation map'' to determine whether there are differences in renal tissue oxygenation during vascular occlusion with AO vs AV. Materials and Methods: Renal vascular occlusion with either AO or AV was performed for 60 minutes in seven porcine renal units. Using HSI, the percentage of oxyhemoglobin (%HbO(2)) in the renal cortex was determined at 4-minute increments throughout the ischemic period and for 30 minutes after reperfusion. Results: Average baseline % HbO(2) in all animals was approximately 70%. After vascular occlusion in both cohorts, % HbO(2) decreased by one third within 2 to 5 minutes, with a gradual decline in % HbO(2) over the remaining 55 minutes. Oxyhemoglobin profiles for AO and AV occlusion diverged significantly between 16 and 24 minutes after vascular occlusion (P = 0.0001 and 0.036, respectively), with a merging of the two curves occurring after approximately 36 minutes (P = 0.093). During reperfusion, average % HbO(2) improved to 72.4% after 25 to 30 minutes. Conclusion: In this pilot study, we demonstrate that renal tissue oxygenation drops rapidly after occlusion of the renal vasculature and returns to near baseline 30 minutes after reperfusion. In the porcine model, the % HbO(2) differs significantly between AO and AV occlusion for up to 35 minutes after ischemia onset, indicating a possible ischemic window'' in which AO occlusion may provide benefit over AV occlusion.