The following points became clear in the present study: (1) The plasma BNP concentration is significantly increased in patients with cardiac arrest and return of spontaneous circulation (ROSC) during TH; (2) the BNP secretion is not related to hemodynamics, suggesting the possibility of stimulation by hypothermia; and (3) the BNP levels are significantly greater than those of ANP in cold environments. This evidence concerns the gene NPPA and cardiac arrest.