Effects Of Different Doses Of Dexamethasone On Postoperative Cognitive Dysfunction In Elderly Patients Undergoing Orthopedic Joint Replacement Surgery

Objective: To investigate the influence of preoperative administration of different doses of dexamethasone on postoperative cognitive dysfunction(POCD),and to explore the prevention and treatment of dexamethasone on POCD.Methods: In this prospective randomized trial,100 patients(ASA Ⅰ-Ⅲ,aged 65 years or older)undergoing orthopedic joint replacement(including unilateral total hip replacement and unilateral total knee replacement)were randomly divided into three groups: control group(n=33),Dex-A(n=33),and Dex-B(n=34).30 minutes before induction of anesthesia,Dex-A group received intravenous injection of dexamethasone 0.05 mg/kg,Dex-B group received intravenous dexamethasone 0.15 mg/kg,and control group received intravenous injection of 0.9% sodium chloride equal volume.Propofol and fentanyl were administered for anesthetic induction,whereas propofol and remifentanil were given for maintenance of anesthesia.The serum levels of TNF-α,S100β protein,neuron specific enolase(NSE)was administered preoperatively and on 1d,5d postoperatively,and the cognitive function was tested on the same time with mini-mental state examination(MMSE).MMSE has to be guided by experienced physician,patients who experienced >2 deficits were considered to have experienced early POCD.Results: There was no significant difference in the preoperative MMSE scores between the three groups(P>0.05).Compared with the preoperative one day,the MMSE scores of the control group and Dex-A group were significantly lower at the first and fifth days postoperatively(P<0.05).Compared with the control group,the MMSE scores of the Dex-B group at the first and fifth days postoperatively increased significantly(P<0.05).On the first postoperative day,the morbidity of POCD in control group was 36.4%,Dex-1 group was 27.3%,Dex-2 was 14.7%.Compared with the control group,the incidence of POCD in the Dex-A group had no significant difference(P>0.05),while the incidence of POCD in the Dex-B group decreased significantly(P<0.05).On the fifth postoperative day,the morbidity of POCD in control group was 27.3%,Dex-1 group was 18.2%,Dex-2 was 8.8%.Compared with the control group,the incidence of POCD in the Dex-A group had no significant difference(P>0.05),while the incidence of POCD in the Dex-B group decreased significantly(P<0.05).There was no significant difference in the levels of serum of TNF-α,S100β protein and NSE between three groups before surgery(P>0.05).Compared with one day before surgery,the levels of serum of TNF-α,S100β protein and NSE in three groups were significantly increased on the first postoperative day(P<0.05),the levels of serum of TNF-α,S100β protein and NSE in control group and Dex-A group were significantly increased on the fifth postoperative day(P<0.05),while there was no significant difference in Dex-B group on the fifth postoperative day(P>0.05).Compared with the control group,the levels of serum of TNF-α,S100β protein and NSE concentrations in the Dex-A group had no significant difference on the first day and the fifth day after operation(P>0.05),while there was significant reduction in Dex-B group(P<0.05).Compared with Dex-A group,the levels of serum of TNF-α,S100β protein and NSE concentrations in Dex-B group were significantly decreased on the first and fifth day after operation(P<0.05).Conclusions: Pretreatment with 0.15mg/kg dexamethasone can decrease the incidence of POCD in the early postoperative period after orthopedic joint replacement,its mechanism may be related to relieving the inflammation activated by surgery and diminishing inflammatory mediators such as TNF-α,and reducing the release of S100β protein,NSE.