Comparison of the effects of minimal flow anesthesia in geriatric and adult patients

Minimal flow anesthesia (MFA) has significant advantages such as reducing costs and environmental pollution, as well as a protective effect on the respiratory tract. It was hypothesized that MFA could be more easily applied in geriatric patients due to the reduction in oxygen consumption and anesthetic requirement. To investigate this, the effects and safety of MFA on geriatric and adult patient populations were compared. In this prospective study, 80 patients (40 patients aged 18-50 years and 40 patients aged 65 years and older) with American Society of Anesthesiology (ASA) classification I-III who were undergoing abdominal surgery under general anesthesia were included. Patients were admitted to the operating room without premedication and underwent bispectral index (BIS) and cerebral oximetry monitoring in addition to routine monitoring. After endotracheal intubation, fresh gas flow (FGF) was reduced to 350 mL/min following a high flow period with desflurane in an O2/air mixture. Gas concentrations, hemodynamic data, cerebral oxygenation, and depth of anesthesia were monitored throughout the operation. Desflurane was adjusted to maintain a BIS value of 40-50. Oxygen concentration in the FGF (FGO2) was increased or decreased by 10% to keep oxygenation parameters within safe limits. The number of changes in oxygen and desflurane concentrations were recorded. While the depth of anesthesia and oxygenation parameters were maintained within safe limits in all patients, the total number of changes and increases in FGO2 were significantly lower in the geriatric patient group. Regional cerebral oxygen saturation levels were within clinically acceptable values. There was no difference between the groups in terms of changes in desflurane concentration. In conclusion, the study findings indicate that MFA, when administered at 350 mL/min in geriatric patients, requires fewer adjustments compared to the younger population, while effectively preventing hypoxia and ensuring an adequate depth of anesthesia