Optimal inhaled oxygen and carbon dioxide concentrations for post-cardiac arrest cerebral reoxygenation and neurological recovery

Prolonged cerebral hypoperfusion after the return of spontaneous circulation (ROSC) from cardiac arrest (CA) may lead to poor neurological recovery. In a 7-min asphyxia-induced CA rat model, four combinations of inhaled oxygen (iO(2)) , carbon dioxide (iCO(2)) were administered for 150 min post-ROSC and compared in a randomized animal trial. At the end of administration, the partial pressure of brain tissue oxygenation (PbtO2) monitored in the hippocampal CA1 region returned to the baseline for the 88% iO(2) [DPbtO(2), me-dian:-0.39 (interquartile range: 5.6) mmHg] and 50% iO(2) [DpbtO(2),-2.25 (10.9) mmHg] groups; in contrast, PbtO(2) increased substantially in the 88% iO(2)+12% iCO(2) [DpbtO(2), 35.05 (16.0) mmHg] and 50% iO(2)+12% iCO(2) [DpbtO(2), 42.03 (31.7) mmHg] groups. Pairwise comparisons (post hoc Dunn's test) indi-cated the significant role of 12% iCO(2) in augmenting PbtO(2) during the intervention and improving neuro-logical recovery at 24 h post-ROSC. Facilitating brain reoxygenation may improve post-CA neurological outcomes.