Systemic impact on secondary brain aggravation due to ischemia/reperfusion injury in post-cardiac arrest syndrome: a prospective observational study using high-mobility group box 1 protein

BACKGROUND: Ischemia/reperfusion injury (I/R) is an important pathophysiology of post-cardiac arrest syndrome (PCAS) against multiple organ dysfunction and mortality. The inflammatory response in PCAS causes systemic I/R. The purpose of this study was to demonstrate the pathophysiology of systemic I/R for secondary brain damage using the biomarkers high-mobility group box 1 (HMGB1), neuron-specific enolase (NSE), and interleukin-6 (IL-6). METHODS: This study was designed as a single-institution prospective observational study. Subjects were observed for 90 days, and neurological outcome was classified according to the Glasgow-Pittsburgh Cerebral Performance Categories Scale (CPC). Serum HMGB1, NSE, and IL-6 were evaluated for variability, correlation with each biomarker, or the Sequential Organ Function Assessment (SOFA) score and CPC at return of spontaneous circulation at 0, 24, 48, and 168 h. RESULTS: A total of 128 patients were enrolled in this study. Initial HMGB1 correlated with CPC (ρ = 0.27, p = 0.036) and SOFA score (ρ = 0.33, p < 0.001). The early phase of HMGB1 (0–24 h), all phases of IL-6, and the delayed phase of NSE (24–168 h) manifested poor neurological outcome. HMGB1 showed a significant correlation with NSE (ρ = 0.29, p = 0.002 at 0 h; ρ = 0.42, p < 0.001 at 24 h) and IL-6 (ρ = 0.36, p < 0.001 at 24 h). CONCLUSIONS: Serum HMGB1 for first 24 h after cardiac arrest was significantly correlated with SOFA score, NSE, and IL-6. This result suggests that systemic I/R may contribute to secondary brain aggravation. It is expected that research on HMGB1 focused on systemic I/R will help prevent aggravating neurological outcomes.