Comparison of automated control method and manual control method in minimal flow anesthesia

AIM: The administration of inhaler anesthetics and the fresh gas flow (FGF) rate can be automatically controlled by new generation anesthesia machines. In our study, we compared the application of minimal flow methods by an ACA, which is an automatically controlled module of the Mindray A9® (Shenzhen, China) anesthesia machine, and manually by an anesthesiologist in patients undergoing gynecological surgery under general anesthesia. We aimed to compare cost of AA consumption, hemodynamic parameters, depth of anesthesia, time to reach target AA concentrations, awakening time and workload of anesthetists. MATERIALS AND METHODS: After obtaining approval from the local ethics committee for the study, written informed consent was obtained from all patients before the study. In this study, we randomly divided 76 patients who underwent gynecological surgery into two groups: and the manual controlled anesthesia group (Group MCA), the automatic controlled anesthesia group (Group ACA). In group MCA (n=38), induction was performed with a mixture of 40-60% O 2 and air with a 4 L/min fresh gas flow (FGF) and sevoflurane vaporizer was set %2,5 until the minimum alveolar concentration (MAC) reached 1. Then, MAA was initiated with 0.5 L/min FGF. The target FIO 2 value was determined as 35-40%. In group ACA (n=38), the MAK was determined as 1 and the FiO 2 was adjusted as 35%. Anesthesia and operation times, MAC, hemodynamic parameter, depth of anesthesia, time to reach target Et-AA value, number of ventilator adjustments, volatile agent consumption, awakening times were analyzed. (Clinical Trials Number: NCT05554263). RESULTS: There was no statistically significant difference in depth of anesthesia, hemodynamic stability and anesthetic agent consumption between the two groups (Sevoflurane consumption: MCA: 17.2 ± 4.5, Group ACA: 19.1 ± 4.9 ml; p=0.076) It was observed that the MAK 1 target was achieved significantly faster in anesthesia administered with ACA mode (Group MCA: 314 ± 169 sec ; Group ACA: 218 ± 51 sec). The total number of vaporizer adjustments according to the depth of anesthesia was 217 in the MCA group and 15 in the ACA group. CONCLUSION: Based on the results of our study, we have shown that the ACA mode is more advantageous than manual modes in terms of reaching target anesthetic agent concentrations more quickly and the number of adjustments required to achieve a constant depth of anesthesia.