The association between inflammatory indices and mortality in geriatric carbon monoxide poisoning

Carbon monoxide (CO) poisoning poses a significant threat to the geriatric population, who experience disproportionately high mortality rates. This study aimed to evaluate the prognostic utility of systemic inflammatory indices and novel composite biomarkers for predicting mortality in elderly patients with CO poisoning. A retrospective cohort study was conducted on 36 geriatric patients (≥ 65 years) admitted to the emergency department with acute CO poisoning. Demographic, clinical, and laboratory data were collected, including complete blood count, biochemistry, arterial blood gas values, and calculated inflammatory indices (NLR, PLR, SII, SIRI, CAR, MAR, RDW/lactate, COHb/lactate). The primary outcome was in-hospital all-cause mortality. While traditional inflammatory indices (SII, SIRI, NLR, PLR) showed no significant association with mortality, the novel COHb/lactate ratio demonstrated exceptional discriminatory power. Non-survivors exhibited significantly higher median creatinine, WBC, hemoglobin, COHb, and lactate levels, but significantly lower RDW/lactate, pH, HCO₃-, and COHb/lactate ratios. ROC analysis revealed an AUC of 0.956 (p = 0.032) for the COHb/lactate ratio in predicting survival. An optimal cut-off value of < 3.61 was identified, yielding a sensitivity of 94.12% and specificity of 100%. The results indicate that conventional inflammatory indices may lack prognostic specificity in geriatric CO poisoning, likely due to the dominant pathophysiology of acute hypoxic-ischemic injury and age-related alterations in inflammatory response. In contrast, the COHb/lactate ratio, which integrates direct markers of exposure and metabolic consequence, emerges as a superior, highly specific biomarker for risk stratification and mortality prediction in this vulnerable population.