Effect Of Postoperative Continuous Infusion Of Dexmedetomidine On Cognitive Function In Elderly Patients With General Anesthesia After Total Hip Arthroplasty

Background:Postoperative Cognitive Dysfunction（POCD）is a common neurological complication after surgery,especially in elderly patients,the main manifestations are inability to concentrate,memory loss,personality changes,and mental disorders.At present,the specific pathogenesis of POCD is still not very clear.According to the theory of inflammation,the inflammatory response of the central nervous system may be an important mechanism for causing POCD,surgical trauma can activate the immune system and produce a strong peripheral inflammatory response,peripheral inflammatory factors act on the central nervous system through various pathways,stimulate microglia,which releases cytokines IL-1,IL-6,TNF-αand other inflammatory mediators.High concentrations of inflammatory factors can produce neurotoxicity and cause neurodegeneration,resulting in impaired cognitive function.Dexmedetomidine（DEX）is a highly selectiveα₂adrenergic receptor agonist with good sedative and analgesic effects,it is widely used in clinical practice because of its advantages such as being conducive to the stability of breathing and circulation,current research suggests that preoperative and intraoperative DEX application can reduce the level of postoperative inflammatory factors,and has a significant preventive effect on postoperative cognitive dysfunction.In previous studies,the application of DEX was mostly focused on intraoperative or preoperative,but the study found that the highest concentration of inflammatory factors did not appear on the day of surgery after hip replacement,it is 48h～60h after operation,so whether continuing DEX application after operation is more beneficial to the brain protection of elderly patients and whether it can better improve the postoperative cognitive function of patients deserves our attention.Objective:To observe the effect of continuous application of DEX on postoperative inflammatory factor levels and cognitive function in elderly patients undergoing general anesthesia and total hip arthroplasty,and to observe its safety to provide clinical evidence for the prevention and treatment of POCD in elderly patients.Methods:A total of 150 elderly patients（60-80 years old）who were going to undergo elective total hip replacement surgery under general anesthesia from June 2020 to December 2021 were selected,and the 150patients were divided into D₁,D₂,and S by random number table method.Group 3 groups,50 cases in each group.Groups D₁and D₂:Before induction of anesthesia,DEX loading dose of 0.5μg/kg was intravenously infused for 15 minutes,and then maintained at 0.2μg/kg·h;After the operation,the D₂group was continuously injected with DEX 0.2μg/kg·h by intravenous pump until 72 hours after the operation,and the D₁group was stopped after the operation,and the same volume of normal saline was used as the same volume as the D₂group.In group S,equal volume of normal saline was given for maintenance before operation,during operation and after operation.The three groups of patients were recorded with age,sex,BMI,years of education,amount of bleeding,amount of fluids,time of anesthesia,time of surgery,amount of urine,and time of extubation.The changes in cognitive function of the three groups were double-blindly assessed by the Mini Mental State Examination（MMSE）at 24 hours before surgery（T₀）,the first day after surgery（T₁）,the third day after surgery（T₂）,and the 7th day after surgery（T₃）.Serum IL-1,IL-6,TNF-αlevels were measured by enzyme linked immunosorbent assay（ELISA）at 24 hours（T₀）,postoperative day 1（T₁）,postoperative day 3（T₂）,and postoperative day（T₃）.Results:（1）The difference was not statistically significant in the general conditions of the three groups,such as age,sex,BMI,years of education,amount of bleeding,amount of fluids,amount of rehydration,time of anesthesia,time of surgery,amount of urine,and time of extubation,and the difference was not statistically significant（p>0.05）.（2）24 hours before surgery（T₀）,the mm SE scores of the three groups were compared,and the difference was not statistically significant（p>0.05）,and the difference in serum IL-1,IL-6,TNF-αlevels was not statistically significant（p>0.05）.（3）On the first day after surgery（T₁）,the MMSE scores of the three groups were reduced compared with T₀,and the serum IL-1,IL-6,TNF-αlevels were increased,and the difference was statistically significant（p<0.05）;Compared with the S group,the MMSE scores of the D₁and D₂groups were significantly higher,and the number of cases of POCD was significantly less,and the serum IL-1,IL-6,TNF-αlevels were significantly reduced.The difference was statistically significant（p<0.05）;D₁compared with the D₂group,the MMSE score in the D₂group was significantly increased,and the number of occurrences was smaller,and the serum IL-1,IL-6,TNF-αlevels were significantly reduced,and the difference was statistically significant（p<0.05）.（4）On the 3rd day after operation（T₂）,compared with T₀,the MMSE scores of D₁and S groups were decreased,and the difference was statistically significant（p<0.05）;Compared with T₀,there was no significant difference in MMSE score in group D₂（p>0.05）;The serum levels of IL-1,IL-6,and TNF-αin the three groups were all higher than those at T₀,and the difference was statistically significant（p<0.05）.Compared with the S group,the MMSE scores of the D₁and D₂groups were significantly higher,and the number of POCD cases was significantly lower,and the serum levels of IL-1,IL-6,and TNF-αwere significantly lower,and the difference was statistically significant（p<0.05）;Compared with the D₁group,the MMSE score of the D₂group was significantly increased,and the number of cases of POCD was significantly lower,and the serum levels of IL-1,IL-6,and TNF-αwere significantly decreased,and the difference was statistically significant（p<0.05）.（5）On the 7th day after operation（T₃）,compared with T0,the MMSE scores of D₁and S groups were decreased,and the difference was statistically significant（p<0.05）;Compared with T₀,there was no significant difference in MMSE score between D₂group（p>0.05）.The serum levels of IL-1,IL-6 and TNF-αin the three groups were not significantly different from those at T₀,and the difference was not statistically significant（p>0.05）,there was no significant difference in serum IL-1,IL-6 and TNF-αlevels among the three groups at T₃（p>0.05）.Compared with the S group,the MMSE scores of the D₁and D₂groups were significantly higher,and the number of POCD cases was significantly lower,and the difference was statistically significant（p<0.05）;Compared with the D1 and D₂groups,the MMSE score of the D₂group was increased,and the number of POCD cases was significantly less,and the difference was statistically significant（p<0.05）.Conclusion:Dexmedetomidine continued to be used until 72 hours after surgery can reduce the expression levels of inflammatory factors IL-1,IL-6 and TNF-αin serum of elderly patients with general anesthesia undergoing total hip arthroplasty,improve postoperative cognitive function,and effectively prevent the occurrence of postoperative cognitive dysfunction.It is beneficial to the patient’s recovery after surgery.