Cerebral Oximetry during Out-of-Hospital Resuscitation: Pilot Study of First Responder Implementation

<b>Background:</b> Anoxic brain injury is a common mode of death following out-of-hospital cardiac arrest (OHCA). We assessed the course of regional cerebral oxygen saturation (rSO₂) at the outset and during first responder resuscitation to understand its relationship with return of spontaneous circulation (ROSC) and functional survival. <b>Methods:</b> We undertook a prospective observational investigation of adult OHCA patients treated by a first-responder EMS agency in King County, WA. Cerebral oximetry was performed using the SenSmart® Model X-100 Universal Oximetry System (Nonin Medical, Inc). We determined cerebral oximetry rSO₂ overall and stratified according to ROSC and favorable survival status defined by Cerebral Performance Category (CPC) of 1-2. <b>Results:</b> Among the 59 OHCA cases enrolled, 47% (<i>n</i> = 28) achieved ROSC and 14% (<i>n</i> = 8) survived with CPC 1-2. On average, initial rSO₂ cerebral oximetry was 41% and was not different at the outset according to return of spontaneous circulation (ROSC) or survival status. Within 5 minutes of first responder resuscitation, those who would subsequently achieve ROSC had a higher rSO₂ than those who would not achieve ROSC (51% vs. 43%, <i>p</i> = 0.03). Among patients who achieved ROSC, those who would survive with CPC 1-2 had a higher rSO₂ cerebral oximetry following ROSC than nonsurvivors (74% vs. 60%, <i>p</i> = 0.04 at 5 minutes post ROSC), a difference that was not evident in the minutes prior to ROSC (55% vs. 51% at 3 minutes prior to ROSC, <i>p</i> = 0.5). <b>Conclusion:</b> In this observational study, where first responders applied cerebral oximetry, higher rSO₂ during the course of care predicted ROSC among all patients and predicted favorable survival among those who achieved ROSC. Future investigation should evaluate whether and how treatments might modify rSO₂ and in turn may influence prognosis.