Comparison of automatic gas control mode and minimal flow in breast surgery

Aim: The automatic gas control (AGC) mode is applied by the anesthesia device automatically providing the targeted end-tidal anesthetic agent (EtAA) and oxygen (O2) concentrations in low-flow anesthesia management. In our study; we aimed to compare the effects of AGC mode and minimal flow technique with manual gas control on inhaler anesthetic agent consumption-cost, hemodynamics and recovery in breast surgeries. Materials and Methods: The prospective randomized study, approved by the ethics committee, included 90 patients aged 18-65 years, in the American Society of Anesthesiologists (ASA) I-II risk group, who were planned for breast surgery under general anesthesia under elective conditions. The patients were divided into three groups: AGC mode (Group 1, n:30), manual gas control mode with minimal flow (Group 2, n:30), and manual gas control mode with medium flow (Group 3, n:30). Routine hemodynamic monitoring, body temperature and bispectral index (BIS) monitoring were performed. Routine anesthesia induction was applied to all patients after preoxygenation. Maintenance was provided with sevoflurane and intravenous (i.v) remifentanil infusion. Medical air was used as the carrier gas. In all three groups, after reaching the minimum alveolar concentration (MAC) value of 1.0, sevoflurane level was adjusted to keep BIS value between 40-60 in maintenance. Mean arterial pressure (MAP), heart rate (HR), peripheral oxygen saturation (SpO2), BIS, inspired sevoflurane fraction (FiSEVO), expired sevoflurane fraction (FeSEVO), end-tidal carbon dioxide (EtCO2), body temperature and the amount of instantaneously consumed inhaler anesthetic agent were recorded before induction and intraoperative time intervals. Extubation, recovery, total surgery and anesthesia times were recorded. At the end of each case, the total amount of inhaled anesthetic agent consumed was determined and cost analysis was performed. Results: It was observed that hourly consumption of sevoflurane in Group 1 was less than Group 2 and Group 3 (p<0.001, p<0.001, respectively), and Group 2 consumption was less than Group 3 (p<0.001). In the cost calculation due to sevoflurane consumption, Group 1 values were found to be significantly lower than Group 2 and Group 3 values (p<0.001, p<0.001, respectively), and Group 2 values were lower than Group 3 values (p<0.001). MAP values were found to be similar between groups (p>0.05). In the pre-extubation body temperature measurements, Group 1 values were found to be higher than Group 2 and Group 3 values (p=0.014, p=0.002, respectively), while Group 2 and Group 3 values were found to be similar. It was determined that the extubation time was longer in Group 2 than Group 1 and Group 3 (p<0.001, p<0.001, respectively), while Group 1 and Group 3 values were similar. There was no significant difference between the groups in terms of recovery times (p>0.05). Conclusion: We believe that the use of AGC mode is superior to the minimal flow technique with manual gas control, since it does not have a negative effect on hemodynamics and recovery and reduces the consumption of inhaler anesthetic agents.