Value of systemic immune inflammatory index on secondary cerebral infarction in patients with acute severe carbon monoxide poisoning

This study aimed to explore the discriminative ability of the systemic immune inflammatory index (SII) on cerebral infarction (CI) in patients with acute severe carbon monoxide poisoning (ASCMP). A retrospective cohort study was conducted including 139 patients with ASCMP who were hospitalized in the emergency medicine department of Harrison International Peace Hospital from January 2019 to January 2026. All patients were tested for changes in SII levels, neutrophil/lymphocyte ratio (NLR), and platelet/lymphocyte ratio (PLR), and the occurrence of CI was recorded. According to whether CI occurred or not, they were divided into the CI group (19 cases) and non-CI group (120 cases). Stepwise logistic regression was performed to analyze the influencing factors of CI. The receiver operating characteristic (ROC) curve was constructed, the area under the curve (AUC) was calculated, and the discriminative ability of SII for secondary CI in patients with ASCMP was evaluated. The levels of SII, NLR, and PLR in the CI group [SII(× 10 9 /L): 4053.18 ± 1744.09 vs. 1911.35 ± 1357.85, NLR: 16.41 ± 5.81 vs. 8.45 ± 5.61, PLR: 360.15 ± 194.78 vs. 217.30 ± 94.00] were higher than those in the non-CI group, and the difference was statistically significant (all P < 0.05). Stepwise Logistic regression analysis showed that the increase of SII and lactic acid, the decrease of Glasgow score were risk factors for CI (all P < 0.05). Utilizing CI as the state variable, ROC curve analysis showed that the AUC of SII was 0.889, and the diagnostic efficiency was the highest when the critical value was 2128.79 × 10 9 /L, with sensitivity of 0.947 and specificity of 0.708. Elevated SII is an associated biological marker for secondary CI in patients with ASCMP, and shows discriminative ability for secondary CI.