Therefore, the elevated serum complement activation products, including C3a, C5a, and sC5b-9, have been reported to be associated with post-cardiac arrest immunoinflammatory response and poor prognosis [7, 11, 29], which is consistent with our result that the non-survivors had higher concentrations of serum C3a, C5a and sC5b-9 than the survivors. This evidence concerns the gene C3 and cardiac arrest.