Objective To compare the effects of different doses of dexmedetomidine on the median effective concentration (EC50) of ropivacaine for epidural block and investigate the appropriate dose.Methods One hundred and twenty ASA Ⅰ patients of both sexes,aged 20-55 yr,weighing 50-75 kg,scheduled for knee arthroscopic operation,were randomly divided into 4 groups (n =30 each):no dexmedetomidine group (group D0),0.25 μg/kg dexmedetomidine group (group D0.25),0.50μg/kg dexmedetomidine group (group D0.50),and 1.00μg/kg dexmedetomidine group (group D1.00).In group D0,ropivacaine 20 ml was injected into epidural space.The ropivacaine-dexmedetomidine mixtures containing 0.25,0.50 and 1.00 μg/kg dexmedetomidine were injected into epidural space in groups D0.25,D1.00 and D0.50 respectively.The volume of mixtures was 20 nl in groups D0.25,D1.00 and D0.50.The initial concentration of ropivacaine was set at 0.40 ％,0.40 ％,0.28 ％ and 0.20 ％ in groups D0,D0.25,D0.50 and D1.00 respectively and then the EC50 was determined by up-and-down technique.The concentration of ropivacaine was increased/decreased by 0.02％ in the next patient.The analgesic effect was assessed using VAS score.VAS score =0 was considered as effective analgesia.The EC50 and 95％ confidence interval (CI) of ropivacaine were calculated using probit method.Adverse effects were recorded.Results The EC50 and 95 ％ CI of ropivacaine was 0.38％ (0.35-0.41)％,0.34％ (0.31-0.36)％,0.22％ (0.20-0.24)％ and 0.14％ (0.12-0.15) ％ in groups D0,D0.25,D0.50 and D1.00 respectively.The EC50 of ropivacaine was decreased gradually in groups D0,D0.25,D0.50 and D1.00 ( P ＜ 0.05).Compared with group D0,the incidonce of hypotension and bradycardia was significantly increased in group D1.00 ( P ＜ 0.05),while no significant change was found in the incidence of adverse effects in groups D0.25 and D0.50 (P ＞ 0.05).Conclusion The appropriate dose of dexmedetomidine for epidural analgesia is 0.50 μg/kg.

BACKGROUND:Traumatic spinal cord injury primarily relies on scale assessment and imaging examinations in clinical practice.However,there are limitations in predicting the prognosis of the injury.Therefore,the use of metabolomics technology for biomarker screening is significant for estimating the extent of damage,injury and recovery,as well as developing new therapies. OBJECTIVE:To characterize the metabolic features of patients with traumatic spinal cord injury using metabolomics technology and explore potential biomarkers and disrupted metabolic pathways. METHODS:Serum and urine samples were collected from 20 patients with traumatic spinal cord injury(observation group)and 10 healthy subjects(control group).Metabolites were analyzed and multivariate statistical analysis was then performed for data processing to screen differential metabolites.Metabolic pathway enrichment was performed using MetaboAnalyst software.Logistic regression was applied to construct a biomarker combination model,and its relationship with the American Spinal Injury Association grading was analyzed. RESULTS AND CONCLUSION:Significant differences in 160 and 73 metabolites were detected in the serum and urine samples of the two groups,respectively.Pathway enrichment analysis showed evident disturbances in lipid metabolism after traumatic spinal cord injury,including sphingolipid,arachidonic acid,α-linolenic acid,and arachidonic acid metabolism,as well as glycerophospholipid and inositol phosphate biosynthesis.The combination of two identified biomarkers,telmisartan and quercetin glycoside,showed a correlation with the American Spinal Injury Association grading in both serum and urine levels.Thus,metabolomics technology provides assistance in further understanding the pathological mechanisms of traumatic spinal cord injury and screening therapeutic targets.The identified metabolic biomarker combination may serve as a reference for assessing the severity of traumatic spinal cord injury.