Association of baseline serum vitamin C levels with systemic inflammatory response syndrome in critically ill patients ‒ An observational study.

Purpose: vitamin C plays a pivotal role in critically ill patients, yet research on baseline serum vitamin C levels admitted to the Intensive Care Unit (ICU) is lacking. This study investigated the correlation between baseline serum vitamin C levels and critical illness scores to unravel the association between vitamin C levels and systemic inflammatory response syndrome (SIRS). Methods: a total of 340 patients admitted to the ICU between January 2021 and January 2022 were included in this study. Initial serum vitamin C concentration was tested at the time of admission to the ICU. Physiological and biochemical differences among different vitamin C groups were compared. Additionally, the correlations between low baseline serum vitamin C levels and critical illness scores were analyzed. Results: in total, there were 126 (40.8 %) patients in the sufficient vitamin C group, 80 (25.9 %) patients in the insufficient group, and 103 (33.3 %) patients in the deficient group. Compared to the Acute Physiology and Chronic Health Evaluation II (APACHE II), Nutritional Risk Screening (NRS), and Sequential Organ Failure Assessment (SOFA) scores, the SIRS score demonstrated better predictive value for vitamin C deficiency, with an area under the curve (AUC) of 0.674 (p = 0.000). Combining SIRS and APACHE II scores further improved the predictive value for vitamin C deficiency, with an AUC value of 0.711 (p = 0.000). Conclusion: compared to other scores, the SIRS score showed greater predictive value for baseline serum vitamin C deficiency among critically ill patients. Combining SIRS and APACHE II scores exhibited a higher predictive accuracy for detecting vitamin C deficiency.