In vivo estimation of optical properties of rat liver using single-reflectance fiber probe during ischemia and reperfusion

To quantify the changes in optical properties of in vivo rat liver tissue, we applied diffuse reflectance spectroscopy (DRS) system using single-reflectance fiber probe during ischemia and reperfusion evoked by hepatic portal occlusion (hepatic artery, portal vein and bile duct). Changes in the reduced scattering coefficient mu(s)', the absorption coefficient mu(a), the tissue oxygen saturation StO(2), and the oxidation of heme aa3 in cytochrome c oxidase (CcO) OHaa(3) of in vivo rat liver (n = 6) were evaluated. Heme aa(3) in CcO were significantly reduced (P < 0.05) during ischemia, which indicates a sign of mitochondrial energy failure induced by oxygen insufficiency of liver tissue. We found that OHaa(3) obtained from the proposed method was unchanged immediately after the onset of ischemia and started gradually decreasing at 2 min after the onset of ischemia. Difference in the time course between OHaa3 and the conventional ratio metric analysis with mu(a)(605)/mu(a)(620) reported in literature demonstrates that the proposed method is effective in reduction of optical cross talk between hemoglobin and heme aa3. Our results suggest that DRS technique is applicable and useful for assessing in vivo tissue viability and hemodynamics in liver intraoperatively.