The effect of minimal-flow and high-flow hypotensive anesthesia on oxidative stress

Objective: The main objective of this study was to compare the effects of minimal and high gas flow-controlled hypotension applications on IMA and thiol/disulfide balance, which are indicators of oxidative stress.Methods: Patients undergoing elective tympanoplasty were randomized to two groups as minimal-flow and high-flow anesthesia groups. Minimal flow anesthesia was performed with 5L/min fresh gas flow reduced to 0.4 L/min. High flow was administered as 2 L/min fresh gas. Preoperative and intraoperative SpO2, StO2, EtCO2, mean arterial pressure and heart rate values were recorded. Preoperative and intraoperative IMA, total thiol, native thiol, disulfide, disulfide/native thiol and disulfide/total thiol values were recorded and compared between the two groups. Results: The mean intraoperative arterial pressure was statistically notably higher in the high flow group (p=0.048). The mean intraoperative SPO2 value was remarkably higher in the minimal flow group (p=0.032). The mean EtCO2 value was notably lower in the minimal flow group at 5 minutes and 15 minutes of the operation (p=0.029; p=0.048). The mean preoperative and intraoperative IMA values were statistically notably higher in the minimal flow group compared to the high flow group (for both, p=0.001). There was no remarkable difference between the groups in terms of the other monitored parameters (for all, p>0.05).Conclusion: IMA value was found to be significantly higher with minimal-flow anesthesia. However, no notable difference was found in terms of thiol/disulfide homeostasis, indicating the need for further comprehensive studies in order to draw a definitive conclusion