The Sedative Effects Of Dexmedetomidine With Different Loading Doses In Patients Under Branchial Plexus Block

Objective To observe the sedative effects of dexmedetomidine with different loading doses and its influence on hemodynamics in patients scheduled for upper limb operation under branchial plexus block, and discussing the appropriate loading dose of intravenously administered dexmedetomidine for sedation in branchial plexus block.Methods Eighty patients who were classified as American Society of Anesthesiologists physical status Ⅰ-Ⅱ, scheduled for upper limb operation with branchial plexus block, were enrolled in this study.They were randomly allocated to four groups:dexmedetomidine（D1,D2,D3）groups and midazolam（M）group.Before branchial plexus block under ultrasound guidance,Group D1,D2,D3 and Group M were respectively administered with dexmedetomidine 0.3,0.5,0.8μgkg^-1 and midazolam 0.05mg·kg^-1 infusion for 10 min,followed by a maintenance infusion of dexmedetomidine 0.5μg·kg^-1·h^-1 and midazolam O.OSmg·kg^-1·h^-1. MAP, HR, SpO2 and OAA/S score were recorded at the moment of in operating room,before the branchial plexus puncture,after the branchial plexus puncture,and 5,20,30,40 and 60 min after sedative administration.The incidence of hypotension and bradycardia,and the adjunctive fentanyl administration were observed and recorded.Results Four groups did not have significant difference on MAP and HR. SpO2 at T5 in group M were lower as compared to Group Dex （P<0.05）. Compared with the values at T0, the scores of OAA/S in group D1 were no significant difference and in group D2、D3、M were significantly decreased （P<0.05）. The scores of OAA/S were significantly higher at T2-T7 in Group D1 as compared to Group M （P<0.05）.The scores of OAA/S in group D2 were no significant difference as compared to Group M （P>0.05）. The scores of OAA/S were significantly lower at T3-T5 in Group D3 as compared to Group M （P<0.05）. The prevalence of hypotension, but not that of bradycardia or adjunctive fentanyl administration,exhibited a positive correlation with the dose of dexmedetomidine.Conclusions Intravenous injection the loading dose 0.5μg·kg^-1 of dexmedetomidine, followed by a maintenance infusion of 0.54μg·kg^-1·h^-1, can provide the patients undergoing upper limb operation under branchial plexus block with effective sedation,and it keeps hemodynamic stable with less adverse effects.