Objective To evaluate the effect of dexmedetomidine as a supplementary to combined lumbar plexus-sciatic nerve block for arthroscopic knee surgery.Methods Fifty patients who were scheduled for arthroscopic knee surgery and ASA class Ⅰ or Ⅱ grade,were divided into control group and dexmedetomidine group by random digits table method with 25 cases each.The patients of dexmedetomidine group were given loading dose dexmedetomidine 0.8 μ g/kg(injection time 10 min) by intravenous infusion,then were given maintenance dose 0.4 μμ g/(kg· h) to the end of operation.The patients of control group were given 0.9％ sodium chloride,methods with the dexmedetomidine group.After 10 min,combined lumbar plexus-sciatic nerve block was performed by a nerve stimulator in both groups.Fentanyl 50 μμ g was infused intravenously to the patient whose effect of block was inadequately.The mean arterial pressure (MAP),heart rate (HR),pulse oxygen saturation (SpO2),respiratory frequency at preanesthesia (T0),beginning of dexmedetomidine infusion (T1),beginning of surgery (T2),10 minutes of surgery (T3) and the end of surgery (T4) were recorded,and intraoperative untoward reaction,using of fentanyl and doctor's satisfaction rate were recorded.Results There were no statistical differences in MAP and HR at T0 between the 2 groups (P＞ 0.05).MAP and HR at T2-4 were significantly higher than those at T0 in control group,furthermore MAP and HR at T2-4 in control group were significantly higher than those in dexmedetomidine group [MAP:(137 ± 18) mm Hg(1 mm Hg =0.133 kPa) vs.(107 ± 14) mm Hg,(132 ± 11) mm Hgvs.(107 ± 11) mm Hg,(131±13) mm Hg vs.(95 ± 12) mm Hg;HR:(99 ± 17) times/rmin vs.(88 ± 14) times/min,(99 ± 14) times/min vs.(81 ± 15) times/min,(97 ± 14) times/rmin vs.(76 ± 11) times/min],there were statistical differences (P ＜ 0.05).There were no statistical differences in respiratory frequency and SpO2 between the 2 groups (P ＞0.05),but 2 cases in dexmedetomidine group,5 cases in control group appeared SpO2 ＜0.90,they quickly returned to normal (＞ 0.97) by holding up the submaxilla.The using rate of fentanyl and doctor's satisfaction rate in dexmedetomidine group were significantly better than those in control group [28％(7/25)vs.68％(17/25),100％(25/25) vs.80％(20/25)],there were statistical differences (P＜ 0.05).There were no statistical differences in the using rate of atropine and efedrina,the rate of respiratory depression between the 2 groups (P ＞ 0.05).Conclusion Dexmedetomidine as a supplementary to combined lumbar plexus-sciatic nerve block for arthroscopic knee surgery has effect confirmed,low untoward reaction,high doctor' s satisfaction rate.

BACKGROUND:Changes in skeletal muscle mass have been indicated in studies addressing the effects of low-frequency pulsed magnetic fields on the structure and morphology of the skeletal muscle,but no relevant studies have been conducted on the morphologic changes that occur after chronic exposure to the low-frequency pulsed magnetic field. OBJECTIVE:To observe the effects of chronic exposure to low-frequency pulsed magnetic fields on the maximal voluntary contraction and morphologic indicators of the quadriceps muscle of the leg,thereby providing a reference of muscle morphologic changes for the use of this technique as a strategy for muscle function improvement. METHODS:Seventy healthy subjects were recruited and randomly divided into a test group that received magnetic field stimulation and a control group that underwent sham treatment,with 35 subjects in each group,and the total duration of the trial was 4 weeks.The test group underwent low-frequency pulsed magnetic stimulation for 15 minutes every 48 hours,while the control group underwent sham treatment,with the same intervention interval and duration as the test group.After 4 weeks of intervention,changes in the maximum voluntary contraction value of the quadriceps muscle in different groups were observed,and B-mode ultrasonography was utilized as a means of assessment to observe changes in muscle thickness,muscle cross-sectional area,and pinnation angle indexes. RESULTS AND CONCLUSION:After 4 weeks of chronic exposure to low-frequency pulsed magnetic fields,68 subjects completed the test.The maximum voluntary contraction value of the quadriceps muscle in the test group increased significantly(P=0.000),and the increment was significantly higher than that of the control group(P=0.008).Three indexes related to muscle morphology in the test group were significantly higher than the pre-test values(P=0.000),while in the control group,muscle thickness showed a significant reduction(P=0.020),there was no significant change in the pinnation angle,but a significant increase in the cross-sectional area(P=0.000).Intergroup comparisons revealed that the three indicators related to muscle morphology,including muscle thickness(P=0.012),pinnation angle(P=0.003),and cross-sectional area(P=0.049),were significantly higher in the test group than in the control group.The above data confirmed that the maximum voluntary contraction of the quadriceps muscle was significantly increased in healthy adults after 4 weeks of chronic exposure to the low-frequency pulsed magnetic field,and significant increases in the three muscle morphometric indices of muscle thickness,cross-sectional area,and pinnation angle were observed in the test group,providing a basis of muscle tissue morphology for the use of this technique as an exercise alternative and medical treatment strategy for muscle improvement.