Carboxyhemoglobin as Potential Biomarker for Cardiac Surgery Associated Acute Kidney Injury.

• Carboxyhemoglobin (CO-Hb) was reported to likely reflect hemolysis and inflammation, both risk factors for cardiac surgery–associated acute kidney injury (CSA-AKI). • CO-Hb is easily obtainable and available on routine blood gas in cardiac surgery patients at no additional costs or equipment. • Patients with CO-Hb ≥1.4% at intensive care unit admission showed a significantly higher rate of CSA-AKI. • CO-Hb at intensive care unit admission may serve as a practical and biologically logical biomarker in both clinical and research settings. • Specifically for research purposes, CO-Hb could be used for risk stratification and population enrichment in trials of CSA-AKI prevention to increase statistical power, decrease the sample size, and lower the cost of trials. Carboxyhemoglobin (CO-Hb) is a marker of hemolysis and inflammation, both risk factors for cardiac surgery–associated AKI (CSA-AKI). However, the association between CO-Hb and CSA-AKI remains unknown. A retrospective cohort study. Tertiary university-affiliated metropolitan hospital: single center. Adult on-pump cardiac surgery patients from July 2014 to June 2022 (N = 1,698). None. Patients were stratified into quartiles based on CO-Hb levels at intensive care unit (ICU) admission. A progressive increased risk of CSA-AKI was observed with higher CO-Hb levels at ICU admission. On multivariable logistic regression analysis, the highest quartile (CO-Hb ≥ 1.4%) showed an independent association with the occurrence of CSA-AKI (odds ratio 1.45 compared to the lowest quartile [CO-Hb < 1.0%], 95% CI 1.023-2.071; p = 0.038). Compared to patients with CO-Hb <1.4%, patients with CO-Hb ≥ 1.4% at ICU admission had significantly higher postoperative creatinine (135 vs 116 μmol/L, p < 0.001), higher rates of postoperative RRT (6.7% vs 2.3%, p < 0.001) and AKI (p < 0.001) on univariable analysis and shorter time to event for AKI or death (p < 0.001). CO-Hb ≥ 1.4% at ICU admission is an independent risk factor for CSA-AKI, which is easily obtainable and available on routine arterial blood gas measurements. Thus, CO-Hb may serve as a practical and biologically logical biomarker for risk stratification and population enrichment in trials of CSA-AKI prevention. [ABSTRACT FROM AUTHOR]