Objective:To evaluate the effect of regional oxygen saturation (rSO 2)-guided low-dose norepinephrine on postoperative cognitive dysfunction (POCD) in elderly patients undergoing hip replacement under general anesthesia. Methods:One hundred and twenty patients of both sexes, aged 65-80 yr, with body mass index of 18-24 kg/m 2, of American Society of Anesthesiologists physical statusⅠ-Ⅲ, scheduled for hip replacement under general anesthesia, were divided into 2 groups ( n=60 each) using a random number table method: control group (group C) and low-dose norepinephrine guided by rSO 2 group (group RN). The patients in both groups received superior inguinal fascial space block combined with general anesthesia under laryngeal mask placement.In group C, the fluctuation range of mean arterial pressure (MAP) was not more than 20% of the baseline, vasoactive agents were administered according to the changes in blood pressure, rSO 2 was monitored continuously, but the change rate of rSO 2 was not used as the regulating index.In group RN, norepinephrine was infused continuously via the central vein at 0.01-0.10 μg·kg -1·min -1 after anesthesia induction, the dose was adjusted according to rSO 2, the rSO 2 change rate was maintained≤10%, the fluctuation range of mean arterial pressure was not more than 20% of the baseline, and vasoactive agents were administered when necessary.MAP, end-tidal pressure of carbon dioxide (P ETCO 2) and rSO 2 were recorded after inhalation of oxygen (T 0), at 5 min after anesthesia induction (T 1), at 30 min after skin incision (T 2), at the end of surgery (T 3) and after recovery and extubation (T 4), and the change rate of rSO 2 was calculated.The occurrence of adverse events and amount of vasoactive drugs used were recorded.The cognitive function was assessed using Montreal Scale at 1 day before surgery and 7 days after surgery, and the development of postoperative cognitive dysfunction (POCD) was calculated using Z score.The postoperative hospital stay time was recorded. Results:Compared with group C, MAP and rSO 2 were significantly increased, and the change rate of rSO 2 was decreased at T 1, 2 in group RN ( P<0.05). Compared with group C, the requirement for intraoperative vasoactive drugs was significantly decreased, the consumption of norepinephrine was increased, MoCA total score, attention and delayed recall sub-score were increased at 7 days after surgery, the incidence of POCD was decreased, and the postoperative hospital stay time was shortened in group RN ( P<0.05). Conclusion:Low-dose norepinephrine guided by rSO 2 can decrease the development of POCD in elderly patients undergoing hip replacement under general anesthesia.

Objective:To evaluate the relationship between preoperative plasma trimethylamine oxide (TMAO) concentrations and postoperative delirium (POD) in elderly patients.Methods:One hundred and eighty patients, aged ≥65 yr, of American Society of Anesthesiologists Physical Status classification Ⅱ or Ⅲ, with body mass index of 17-30 kg/m 2, scheduled for elective hip replacement, were enrolled in this study. Venous blood samples were collected at 1 day before surgery, and the plasma TMAO concentrations were measured by high throughput liquid chromatography-tandem mass spectrometry. The patients were divided into 3 groups according to the concentrations of TMAO: low-concentration TMAO group (group L, ≤1.2 μmol/L), moderate-concentration TMAO group (group M, 1.3-1.9 μmol/L), and high-concentration TMAO group (group H, ≥2.0 μmol/L). All patients received superior inguinal fascia iliaca compartment block combined with intravenous general anesthesia. POD was identified by the Confusion Assessment Method-Chinese Reversion scale at 1, 2, 3 and 7 days after operation. The patients were divided into POD group and non-POD group according to whether POD occurred. Binary logistic regression analysis was used to evaluate the relationship between different plasma TMAO concentrations and POD. The receiver operating characteristic curve was used to evaluate the efficacy of plasma TMAO concentrations in predicting the occurrence of POD. Results:There were 60 cases in L group, 67 cases in M group and 53 cases in H group, and the incidence of POD was 12%, 22% and 32% in L, M and H groups, respectively. The incidence of POD was significantly higher in group H than in group L ( P<0.05). The plasma TMAO concentration was significantly higher in POD group than in non-POD group ( P<0.05). Logistic regression analysis showed that the risk of POD was 3.91 times higher in group H than in group L ( P<0.05). The area under the receiver operating characteristic curve of preoperative plasma TMAO concentrations in predicting POD was 0.754 (95% confidence interval 0.671-0.838, P<0.05). When the Youden index was 0.426, the optimal cut-off value of plasma TMAO concentrations was 1.625 μmol/L, and the specificity and sensitivity were 0.795 and 0.631, respectively. Conclusions:Elevated preoperative plasma TMAO concentration is associated with an increased risk of POD in elderly patients, and it has a good predictive value for POD.