Background: Tissue O2 saturation (StO2) is a measure of tissue perfusion and should decrease during active hemorrhage. An initial StO2 value upon trauma center arrival measured concurrently with or prior to vitals, may predict hemorrhagic shock, requiring early blood product transfusion. Our aim was to identify the early StO2 threshold associated with a greater volume of packed red blood cell (PRBC) transfusion 24 h after injury. Methods: All highest tier triage trauma patients from January 2011 to July 2012 were included in this study. The initial StO2 value upon arrival was used for comparison. Results: A total of 632 patients were considered, 74 % of them male with a mean age of 46 years. Initial StO 2 values were available for 325 patients. An StO2 value of 65 % was determined as the cutoff due to the marked increase in PRBC consumption in 24 h. There were 23 patients (7 %) with an StO2 reading <65 % compared to 302 patients with values ≥65 %. Both groups had similar systolic blood pressure (118 vs. 126) and heart rate (99 vs. 95) in the trauma bay. In addition, there was no difference in the initial hemoglobin, pH, or base deficit. An early StO2 value <65 % also led to a greater number of PRBC transfused in 24 h (6.4 vs. 1.7). Regression analysis demonstrated that an StO2 <65 % was the only variable associated with a higher PRBC transfusion volume in 24 h (p = 0.01). Conclusions: An StO2 value <65 % correlates with greater requirement for PRBC transfusion 24 h after injury. This suggests that StO2 can be used as an early marker of hemorrhage which may be superior to traditional vital signs in the trauma population.
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