Relationship between carboxyhemoglobin and oxidative stress-related biomarkers during low-flow and normal-flow anesthesia

Low-flow anesthesia may increase perioperative carboxyhemoglobin (COHb) concentrations because of increased rebreathing and carbon monoxide formation within the anesthesia circuit. Whether these modest changes are associated with alterations in systemic oxidative stress-related biomarkers remains unclear. This study compared perioperative COHb, total antioxidant status (TAS), total oxidant status (TOS), and hypoxia-inducible factor-1α (HIF-1α) during low-flow and normal-flow desflurane anesthesia. In this prospective randomized controlled trial, 130 ASA I non-smoking adults undergoing elective open general surgery lasting at least 2 h were randomly assigned to low-flow (Group LA, n = 65) or normal-flow (Group NA, n = 65) desflurane anesthesia. Venous blood samples were obtained before anesthesia induction (T0), at the end of the second intraoperative hour (T1), and 24 h postoperatively (T2). COHb, TAS, TOS, and HIF-1α concentrations were measured and compared between groups. Correlations between COHb and oxidative stress-related biomarkers were also evaluated. Baseline biomarker concentrations were comparable between groups. Group LA demonstrated significantly higher COHb concentrations at T1 and T2, higher TAS concentrations at T1 and T2, and lower TOS concentrations at T1 and T2 than Group NA (all P < 0.05). HIF-1α concentrations did not differ significantly between groups. No significant correlations were observed between changes in COHb and corresponding changes in TAS, TOS, or HIF-1α. Low-flow desflurane anesthesia was associated with modest increases in perioperative COHb concentrations and differences in global oxidative stress-related biomarkers compared with normal-flow anesthesia. However, perioperative COHb concentrations were not associated with TAS, TOS, or HIF-1α, suggesting that the biological significance of these modest COHb changes remains uncertain.