Effects Of Different Inspired Oxygen Concentrations On Cerebral Oxygen Saturation And Postoperative Delirium In Elderly Patients Undergoing Total Hip Arthroplasty

Objective: To investigate the effects of different fraction of inspired oxygen（FiO₂）during anesthesia maintenance on cerebral oxygen saturation（rSO₂）and postoperative delirium（POD）in elderly patients undergoing total hip arthroplasty,and to record and compare the incidence of postoperative pulmonary complications.Patients and methods: A total of 111 elderly patients who underwent total hip arthroplasty in the Central Hospital from December 2021 to December 2022 were selected as the research objects.The patients were divided into 3 groups using a random number table and named according to the level of fraction of inspired oxygen（FiO₂）: 30% FiO₂（group L）,50%FiO₂（group M）and 70%FiO₂（group H）,with 37 cases in each group.Regional cerebral oxygen saturation（rSO₂）,blood oxygen saturation（SpO₂）,heart rate（HR）,electrocardiogram（ECG）,invasive mean arterial pressure（MAP）and depth of anesthesia were continuously monitored after patients entered the operating room.Arterial blood gas analysis was performed before anesthesia（T₀）,after mechanical ventilation for 1 hour（T₁）,after mechanical ventilation for 2 hours（T₂）,and after tracheal catheter removal for 30 minutes（T₃）.The changes of rSO₂,SpO₂,MAP,arterial PH,arterial partial oxygen pressure（PaO₂）,arterial partial carbon dioxide pressure（PaCO₂）,arterial hemoglobin（HGB）and airway peak pressure（PIP）in T₀,T₁,T₂ and T₃ were observed and compared.Oxygenation index（OI,PaO₂/FiO₂）at each time point was calculated according to the formula.The occurrence of POD was evaluated by simple CAM-CR scale twice a day on the 1st day（D₁）,2nd day（D₂）,3rd day（D₃）and 5th day（D₅）after operation,and the incidence of POD was recorded.Venous blood was collected from patients before surgery（D₀）,1 day after surgery（D₁）,and 2 days after surgery（D₂）,and the changes of marker protein S100β and neuron-specific enolase（NSE）were recorded and compared.Ultrasonography（LUS）was used to evaluate atelectasis in patients with T₀,T₃ and one day after surgery（D₁）,and the number of atelectasis cases was recorded.Results: In elderly patients undergoing total hip replacement,compared with patients with 30% FiO₂,the rSO₂ value,blood oxygen partial pressure,blood oxygen saturation and oxygenation index of patients with 50% FiO₂ and 70% FiO₂ increased,and the difference was statistically significant（P <0.05）.FiO₂ of 30%,50% and 70% had no significant effect on the incidence of POD（P > 0.05）.The concentration of nerve cell damage markers and the incidence of atelectasis in patients with 70% FiO₂ were significantly higher than those in patients with 30% FiO₂ and 50% FiO₂（P < 0.05）.Conclusion: 50% FiO₂ can not only significantly improve cerebral oxygen saturation,but also does not increase the incidence of POD and postoperative atelectasis,so it is more suitable for total hip replacement in elderly patients.