Haemoglobin saturation in the rat liver after ischaemia and reperfusion: study using a laser photometry technique and correlation with changes in liver tissue blood flow.

Tissue oxygenation depends on the volume of oxygen consumed by the tissue and the volume of oxygen supply. This is particularly important in the liver after ischaemia and reperfusion, due to the relatively low oxygen saturation of the portal blood flow, the main source of oxygen to the liver. In this study we established a correlation between the postischaemic liver blood flow and tissue haemoglobin saturation, measured by laser Doppler flowmetry and laser surface photometry, with the purpose of investigating the possible role of a postischaemic imbalance of oxygen delivery/uptake in reperfusion injury. The experimental procedure consisted of the temporary interruption of blood flow to the left lateral and medial lobes of the rat liver in vivo, and subsequent reperfusion after defined periods, recording the postischaemic liver blood flow and liver oxyhaemoglobin saturation. Changes were found in the postischaemic liver blood flow and haemoglobin saturation in all the groups when compared to control values, showing a correlation between the length of the period of ischaemia and the magnitude of the alteration in the reperfusion blood flow and oxygenation. These alterations may be considered as a prolongation of the metabolic condition of ischaemia and may be part of an additional tissue damage upon reperfusion.