Background: To determine the correlation of near-infrared spectrophotometry (NIRS) readings from the liver surface with invasive measurements of blood fl ow and tissue perfusion parameters in an animal
model of endotoxemic shock.
Material/Methods: Laparotomy was performed in 12 Yorkshire piglets, and ultrasound blood fl ow probes were placed on the hepatic artery and portal vein. Hepatic vein, portal vein, and femoral artery catheters were inserted for intermittent blood sampling, and a pulmonary artery catheter was inserted via the jugular vein for cardiac output measurements. Near-infrared spectrophotometry optodes were placed across the right hepatic lobe. Endotoxemic shock was induced by continuous infusion of Escherichia coli lipopolysaccharide 055: B5. Pearson correlations were calculated between the perfusion parameters and the near-infrared spectrophotometry (NIRS) readings.
Results: After endotoxemic shock induction, liver blood fl ow decreased from 144±36 to 62±24 ml*min[sup]–1[/sup]*100 g[sup]–1[/sup]
and oxygen delivery to the liver decreased from 20±6 to 7±4 ml*min[sup]–1[/sup]*100 g[sup]–1[/sup]. Near-infrared spectrophotometry readings of oxyhemoglobin concentration decreased by 11.7±15.1 μmol*L[sup]–1[/sup], and readings of deoxyhemoglobin concentration increased by 12.3± μmol*L[sup]–1[/sup]. There were signifi cant correlations (p0.11) between the oxyhemoglobin readings and liver oxygen delivery(r[sup]2[/sup]=0.58), liver blood fl ow (r[sup]2[/sup]=0.73) and cardiac output (r[sup]2[/sup]=0.80). Deoxyhemoglobin readings highly
correlated (p0.11) with mixed venous lactate (r[sup]2[/sup]=0.87) and with hepatic vein lactate (r[sup]2[/sup]=0.82).
Conclusions: Noninvasive near-infrared spectrophotometry measurements of hepatic oxyhemoglobin and deoxyhemoglobin correlate with liver hemodynamics as well as with global and specifi c organ perfusion parameters and may serve, in the future, as a useful tool to monitor tissue perfusion in septic patients.

Keywords: Cardiac Output - physiology, Femoral Artery - physiology, Hepatic Artery - physiology, Liver - metabolism, Oxygen - blood, Oxyhemoglobins - metabolism, Perfusion, Portal Vein - physiology, Pulmonary Artery - physiology, Regional Blood Flow - physiology, Shock, Septic - metabolism, Spectroscopy, Near-Infrared, Sus scrofa