Measurement of the liver tissue oxygenation by near-infrared spectroscopy

Objective: To study the relation between the liver tissue oxygenation index (TOI), transcutaneously measured with spatially resolved spectroscopy ( a new method of near-infrared spectroscopy or NIRS), the mixed venous oxygen saturation and the blood flow in the different parts of the splanchnic circulation in newborn piglets. Design: Tissue oxygenation index of the liver was measured in six newborn piglets at 33 degreesC, 35 degreesC, 37 degreesC and after a decrease in arterial carbon dioxide pressure (PaCO2). Measurements: Mixed venous oxygen saturation, blood gas analysis and peripheral oxygen saturation were measured at each step. Gastric, proximal jejunal, midgut, distal ileal, splenic and hepatic arterial blood flow were measured by injection of coloured microspheres into the left atrium. NIRS optodes were attached to the skin over the liver and TOI was calculated. Results: No significant changes of TOI of the liver were seen during the increase in temperature or change in PaCO2. TOI correlated well with mixed venous oxygen saturation (r = 0.85), the mid-ileal blood flow (r = 0.57) and the distal ileal blood flow (r = 0.72). Conclusions: Measurement of the TOI of the liver might be a non-invasive way to measure the distal ileal blood flow.