Abstract Body: Introduction
We have developed non-invasive optical devices for concurrent monitoring of cerebral and somatic hemodynamics using frequency-domain diffuse optical spectroscopy (FD-DOS) and diffuse correlation spectroscopy (DCS). Objectives: In a pediatric swine model of asphyxia-associated cardiac arrest, compare cerebral and somatic hemodynamics during asphyxia and CPR and assess their association with return of spontaneous circulation (ROSC) in early (<15 min) and late CPR (15-25 min).

Hypothesis
Cerebral hemodynamics will exceed somatic hemodynamics. Greater hemodynamics, and their temporal increase, during CPR will be associated with return of spontaneous circulation (ROSC).

Methods
Optical cerebral and somatic monitoring was performed on the left forehead and left biceps femoris, respectively, in pediatric swine during asphyxia followed by ventricular fibrillation induction and CPR for a minimum of 15 min, up to 25 min. Animals were eligible for defibrillation at 15 min, and every 2 min thereafter. FD-DOS tissue oxygenation (StO2), total hemoglobin concentration (HbT), and DCS blood flow index (BFI) quantified oxygenation, blood volume (BV), and blood flow (BF), respectively. Wilcoxon signed-rank tests with Bonferroni correction compared cerebral versus somatic hemodynamics in 1-min intervals during asphyxia and CPR. Rank-based mixed-effects models assessed the associations of hemodynamics with ROSC in early and late CPR. For late CPR, only data from animals without ROSC at each respective timepoint were included.

Results
Of 22 animals monitored, 10 achieved ROSC (5 after first defibrillation). Cerebral and somatic hemodynamics differed throughout, but cerebral was not consistently greater. Compared to somatic, cerebral StO2 was lower during asphyxia and the 1st min of CPR but did not differ after. Cerebral BV and BF were greater during asphyxia. Cerebral BV remained greater to the 10th min of CPR but did not differ after; unexpectedly, cerebral BF was lower throughout CPR (Fig. 1). Examining ROSC associations, increasing somatic BV (p<0.001), absolute cerebral StO2 (p<0.003), and increasing cerebral-somatic BF difference (p<0.05) were associated in both early and late CPR. Notably, increasing cerebral BV (p=0.002) was also strongly associated in late CPR.

Conclusion
Advanced optical monitoring during asphyxia and CPR provided novel quantification of cerebral and somatic hemodynamics, their differences, and their associations with ROSC in early and late CPR.