Different Loading Dose Of Dexmedetomidine Infusion During Laparoscopic Cholecystectomy

OBJECTIVE: To investigate the appropriate dose of dexmedetomidine（DEX） infusion during Laparoscopic Cholecystectomy, To provide valuablereference for the clinical use of DEX.METHODS: 80 patients,ASA physical status I-II,aged 20-60 years old,scheduled for Laparoscopic Cholecystectomy（LC） were randomly dividedinto four groups:control group（NS）,dexmedetomidine 0.4ug/kg group（DEX0.4）,dexmedetomidine 0.6ug/kg group （DEX0.6）, dexmedetomidine0.8ug/kg group （DEX0.8）.On admission to the operation room peripheralintravenous catheter（PIV） were placed for infusion,vital signs andauditory-evoked potentials（ERP） were continuously monitored.Dexmedetomidine 0.4ug/kg,0.6 ug/kg and 0.8 ug/kg were infused in tenminutes as loading dose in the DEX0.4group,DEX0.6group and DEX0.8grouprespectively,equal volume of saline were given for the NS group .Anaesthesiawas induced with propofol 1mg/kg,with further doses of propofol（if needed）in 20mg increment titrated to loss of evelash reflex and AAI<30.Fentanyl3ug/kg and Cisatracurium 1.5mg/kg were given for trachea intubation.Dexmedetomidine 0.2ug/kg/h was administered followed intubation besidesthe NS group,the same rate of saline was given for the NS group.Anaesthesiawas maintained with sevoflurane,fentanyl and Cisatracurium. The study drugwas stopped when the cholecyst removaled,and stopped all the anestheticdrugs when the surgery finished.The blood pressure and heart rate were recorded in the following moments:T1-befor initial infusion of the studied drug;T2-after initial infusioncompletion;T3-immediately after tracheal intubation; T4-immediately afterpneumoperitoneum;T5-three minutes after pneumoperitoneum; T6-immediately after tracheal extubation. End-tidal concentrations of sevofluranewere measured continuously and the amount of fentanyl wererecorded.Besides these,recorded the incidence of bradycardia andhypertension.The incidence of agitation,nausea and vomitting, visualanalogue scale value（VAS） were recorded after extubation. venous sampleswere collected in moments T1,T3 and T4,samples underwent centrifugationand plasma was stored in a cold refrigerator at -80℃for evaluating bloodnephrine and norepinephrine levels.RESULTS:1.Compared with NS group,MAP values at the time of T4 and T6 weresignificantly reduced in the DEX0.4group, DEX0.6group and DEX0.8group;HR values at the time of T2 were significantly reduced in the DEX0.6group and DEX0.8group;HR values at the time of T3 and T6 weresignificantly reduced in the DEX0.4group, DEX0.6group and DEX0.8group.2.The consumption of fentanyl and propofol were significantly lower inthe DEX0.4group, DEX0.6group and DEX0.8group compared with the NSgroup;compared with DEX0.4group,the consumption of propofol in theDEX0.8group was reduced significantly;there was no statistical difference inthe End-tidal concentrations of sevoflurane among the groups.3.Compared with NS group, The degree of strain on extubation wassignificantly reduced in the DEX0.4group, DEX0.6group and DEX0.8group.Recovery times after discontinuation of sevoflurane to spontaneous eyeopening,spontaneously breathing,and to tracheal extubation did not differ among the four groups.4.The incidence of bradycardia was signicantly higher in the DEX_0.8group compared with the NS group（35.3%vs5.3%）.5. Compared with NS group,the plasma adrenaline concentration at thetime of T3 and T4 were significantly reduced in the DEX_0.8group, the plasmanoradrenaline concentration at the time of T4 was significantly reduced in theDEX_0.8group.CONCLUSION:1. 0.4ug/kg⁰.8 ug/kg of dexmedetomidine infused during 10 minutesbefore induction of anesthesia followed by a maintenance infusion（0.2ug/kg/h）in LC could reduce the dose of anesthetics,promote hemodynamic stabilityand do not delay recovery.2. 0.8 ug/kg of dexmedetomidine can effectively reduce the release ofadrenaline and noradrenaline induced by intense stimulation.3. When using a DEX infusion as an anesthetic adjuvant,a loading doseof 0.4 ug/kg is recommended to minimizing adverse perioperative sideeffects.