The association between elevated cytokine levels and poor outcomes was reported previously for PCAS.(6,7) Interestingly, TTM failed to lower cytokine levels, and IL-6 levels were even reported to be elevated during this treatment.(6,14) H2 gas inhalation was reported to lower IL-6 levels in an animal cardiac arrest model.(15) Overall cytokine levels were low and remained unchanged in patients with cardiac etiologies, suggesting that inhaled hydrogen might have attenuated the elevation in cytokines at an early phase with TTM. Here, IL6 is linked to cardiac arrest.