Effect of real-time oxygen consumption versus fixed flow-based low flow anesthesia on oxygenation and perfusion: a randomized, single-blind study

Although low-flow anesthesia is widely used due to its various advantages, there are concerns about potential and relative hypoxia. Furthermore, oxygen is also a drug with benefits and adverse effects. We aimed to evaluate and compare the effect of real-time oxygen consumption versus fixed flow-based low flow anesthesia on oxygenation and perfusion and to compare the economic benefits. With ethical approvals and informed consent, participants were randomly assigned to a dynamic group (13 males, and 27 females) receiving fresh gas flows depending on real-time oxygen consumption (dynamic O2: N2O), and a fixed group (20 males, and 13 females) receiving fixed fresh gas flows of 600 mL/min (with O2: N2O of 1:1). Oxygen partial pressure and serum lactate were comparable between groups. However, isoflurane consumed and costs incurred were significantly different. Total oxygen consumption per minute was also significantly lower in the dynamic group than the fixed group. No episodes of hypoxia were observed in either group. Real-time oxygen consumption-based low flow anesthesia is feasible and cost-effective without affecting the patient's global perfusion and outcome.