LAUSR

BACKGROUND Decompensated hemorrhagic shock (DHS) is the leading cause of preventable death in combat casualties. "Golden hour" resuscitation effects on cerebral blood flow and perfusion following DHS in prolonged field care (PFC) are not well investigated. Using an established non-human primate model of DHS, we hypothesized non-invasive regional tissue oxygenation (rSO2) and Transcranial Doppler (TCD) would correlate to the invasive measurement of partial pressure of oxygen (PtO2) and Mean Arterial Pressure (MAP) in guiding hypotensive resuscitation in a PFC setting. METHODS Ten rhesus macaques underwent DHS followed by a 2hr PFC phase (T0-T120), and subsequent 4hr hospital resuscitation phase (T120-T360). Invasive monitoring (PtO2, MAP) were compared against non-invasive monitoring systems (rSO2, TCD). Results were analyzed using t-tests and one-way repeated measures ANOVA. Linear correlation was determined via Pearson's r. Significance = p < 0.05. RESULTS MAP, PtO2, rSO2 and MFV significantly decreased from baseline at T0. MAP and PtO2 were restored to baseline by T15, while rSO2 was delayed through T30. At T120, MFV returned to baseline, while the Pulsatility Index significantly elevated by T120 (1.50 ± 0.31). PtO2 vs rSO2 (R = 0.2099) and MAP vs MFV (R = 0.2891) shared very weak effect sizes, MAP vs rSO2 (R = 0.4636) displayed a low effect size, and PtO2 vs MFV displayed a moderate effect size (R = 0.5540). CONCLUSIONS Though non-invasive monitoring methods assessed here did not correlate strongly enough against invasive methods to warrant a surrogate in the field, they do effectively augment and direct resuscitation, while potentially serving as a substitute in the absence of invasive capabilities.