Clinical Application Of Dexmedetomidine In The Elderly Patients Undergoing Combined Spinal-epidural Anesthesia

Objective: To explore the hemodynamic responses and sedative effect ofdexmedetomidine as an adjuvant in the elderly patients undergoingcombined spinal-epidural anesthesia.Method：Forty-five ASA class I^II elderly patients（26males,19females）aged65-81yr, weighing48-80kg undergoing elective hernia surgeryunder CSEA were randomly divided into three groups（n=15）: group D1、D2and M. After CSEA, the patients of group D1、D2receivedintravenous（IV） dexmedetomidine0.5μg·kg^-1or0.8μg·kg^-1separatelywithin10minutes followed by a maintenance infusion of0.3μg·kg^-1·hr^-1dexmedetomidine. The patients of group M received midazolam0.05mg·kg^-1in10minutes and then infused0.1μg·kg^-1·hr^-1midazolam.Mean blood pressure （MBP）, heart rate （HR）, respiratory rate （RR）,oxygen saturation （SPO2）, auditory evoked potentials index （A-lineARX-index AAI） and Observer’s Assessment of Alertness/Sedation Scale（OAA/S） were evaluated at time points of before （T0） and5min（T1）,10min（T2）,20min（T3）,30min（T4）,60min（T5） after treatment. The sideeffects，such as nausea, vomit, shivering, and so on in patients of thesethree groups were also recorded. Amnestic effects were recorded24 hours after surgery too.Result:There were no significant difference between the general information of three groups （P>0.05）. Compared with To, in group D2, MAP and HR decreased significantly at T2～T5（P<0.05）, and in group M, MAP decreased significantly at T3～T5（P<0.05）. At T2～T5, HR in group D2was lower than that in group D1and M （P<0.05）. MAP in group D2and M were lower than that in group D1（P<0.05）. Compared with baseline, there were significant changes of RR and SPO2in group M at T3～T5, and more significantly than group D1and D2（P<0.05）. OAA/S scores were lower in D1、 D2and M groups at T2～T5than those at To （P<0.05）. At the time points T3～T5, patients’scores in group M were lower than those in dexmedetomidine groups, but no different between group D1and D2. AT the same time, AAI in group D1and D2ranged from40to60, but below40in group M. Amnestic effects among these three groups had no significant difference. The side effects, such as nausea, vomitting, shivering, respiration restrain, happened more commonly in group M.Conclusion:For the aged patients undergoing CSEA, IV dexmedetomidine0.5μg·kg-1within10minutes followed by a maintenance infusion of0.3μg·kg-1-hr-1caused effective sedation and amnestic effect without respiration restrain and cycle inhibition.