Thresholded area over the curve of spectrometric tissue oxygen saturation as an indicator of volume resuscitability in porcine hemorrhagic shock

A rapid, reliable, and noninvasive functional measure of responsiveness to resuscitation in posttraumatic hemorrhagic shock could prove useful in guiding therapy, especially under circumstances such as the battlefield and civilian mass casualties. Tissue oxygen saturation (Sto²) is a promising c and idate for this application. We therefore explored the value of peripheral muscle Sto² in predicting systemic responsiveness to colloid volume resuscitation in a porcine model of hemorrhagic shock. Fourteen isoflurane-anesthetized piglets were subjected to a st and ardized hemorrhage protocol that maintained mean arterial pressure (MAP) between 30 and 40 mm Hg. Asanguineous resuscitation with a volume of Hextend equal to the total volume bled was initiated when compensation was exhausted (MAP <30 mm Hg). We recorded continuous MAP and Sto² values, and calculated the contiguous area over the Sto² curve yet below a given threshold of Sto² (TAOC) as a function of this threshold before the selected timepoint for timepoints up to 30 minutes before resuscitation. Hemorrhage resulted in significant fluctuations of MAP and high interindividual variability of disease dynamics and outcome: 4 nonsurvivors and 10 survivors at 2 hours postresuscitation. Sto² measurements reflected hemodynamic conditions in most animals, with a pronounced drop preceding final decompensation in 7 of 14 animals. TAOC discriminated three of four nonresuscitable (nonsurvivor) animals from the survivors, with group differences reaching significance even for the earliest examined timepoint (30 minutes before resuscitation), depending on the choice of TAOC threshold. Sto² may serve as a marker of decompensation, whereas TAOC, a physiologically motivated correlate of perfusion debt and cumulative hypoperfusion injury, may be a useful early indicator of responsiveness to volume resuscitation in hemorrhagic shock.