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562087 
Journal Article 
Noninvasive Tissue Oxygen Saturation Measurements Identify Supply Dependency 
George, ME; Beilman, GJ; Mulier, KE; Myers, DE; Wasiluk, KR 
2010 
Yes 
Journal of Surgical Research
ISSN: 0022-4804
EISSN: 1095-8673 
In Press, Corrected Proof 
Background Hemorrhagic shock can lead to multiple organ failure and death. We have previously shown that noninvasive measurement of tissue oxygen saturation (StO2) has predictive value for outcomes in patients suffering hemorrhagic shock. Our study objectives were twofold: (1) to compare invasive and noninvasive measurements of local and systemic tissue hemoglobin oxygenation and (2) to compare the effects of various physiologic conditions seen in patients in hemorrhagic shock on tissue hemoglobin oxygenation.Materials and Methods We studied pigs in controlled conditions mimicking shock induced by one of the following: hypothermia, isovolemic hemodilution, or manipulations of vascular tone. We obtained both invasive and noninvasive measurements in a hind limb of StO2, tissue hemoglobin index, femoral artery and venous flows, blood pressures, temperature, pH, pO2, pCO2, oxygen saturation, lactate, hemoglobin, and base excess. In all cases, we measured baseline values in both experimental and control hind limbs.Results We found that tissue hemoglobin oxygenation did not vary significantly over relevant physiologic temperatures. Under all physiologic conditions tested, we found supply-dependent oxygen consumption at oxygen levels less than 7 mL O2/min/kg. Similarly, we found that local oxygen delivery in animals subjected to varying degrees of isovolemic hemodilution or altered vascular tone was correlated with supply-dependent oxygen consumption, as measured by local noninvasive StO2.Conclusions Noninvasive StO2 measurements are valid and durable over a wide range of physiologic conditions and correlate with invasively-measured oxygen delivery. 
tissue oxygenation; StO2; vasoactive treatment; anemia; animal model