The Minimum Effective Dose Of Dexmedetomidine For The Prevention And Treatment Of Shivering Post Combined Spinal And Epidural Anesthesia

Objective: This placebo-controlled study was performed to evaluatethe minimum effective dose of medetomidine (Dex) to preventpostanaesthetic shivering.Methods: We studied120patients (ASA Ⅰ-Ⅲ) scheduled fortransurethral resection of bladder tumor or prostate under spinal andepidural anesthesia.Thirty patients in each group randomly, four groupsnamed①placebo control group (C): saline0.9%②low dose group(DL):0.2ug/kg,③mediate dose group (DM)：0.4ug/kg④high dosegroup (DH):0.6ug/kg. All patients were fasted for8hours before surgery,do not give any preoperative medication. Patients took the right lateralposition, select L3~4vertebra clearance subarachnoid block (2.0ml of0.5%bupivacaine),then epidural catheterization.,then horizontalrecumbent position. Group DL,DM,DH respectively receiveddexmedetomidine0.2ug/kg,0.4ug/kg,0.6ug/kg as group C received saline0.9%,all drugs pumped injection intravenously constant speed for15minutes. Observations include: age, ASA classification, gender, bodyweight, the operation time, infusion volume, flushing volume. To observeand record the mean blood pressure (MBP), heart rate (HR), respiratoryfrequency (RR), pulse oxygen saturation (SPO2), central bodytemperature (T) and Ramsay sedation score（RSS）. Incidence and severity of shivering were recorded. Observe and record the incidence ofadverse drug reactions, including nausea, vomiting, dry mouth,respiratory depression (RR <10beats/min or SpO2<90%of),bradycardia (HR <50times/min).The assessment criteria:⑴center temperature of the body (rectaltemperature, T)<36.5℃is defined as hypothermia;⑵Shivering grading:grand0， no shivering; grand1piloerection or (and) peripheralvasoconstriction or (and) peripheral cyanosis, but no muscle trembling;grand2，only one group of muscles trembling; grand3， more than onegroup of muscles trembling (not spread to the whole body); grand4, thewhole body muscle trembling. The shivering consistent for2min anddoes not disappear, then judged shivering.⑶Ramsay sedation score(RRS):1score, consciousness, patient with anxiety, restlessness orirritable;2scores, consciousness, patient with good cooperation,disorientation or quiet;3scores, conscious, the patients only response tocommand;4scores, sleep, patients have quick responses to tapping theglabella or strong sound stimuli;5scores, sleep, patients have slowreaction to tapping the glabella or strong sound stimulus;6scores, sleep,there is on reflection when tapping the glabella or strong acoustic stimulisto patients.Statistical analyzes were performed using SPSS16.0statisticalsoftware for statistical analysis, the measurement data are presented asmean±standard deviation, group and within-group comparisons using t test, count data using χ2test. P <0.05that the difference was statisticallysignificant.Results: HR in DH group after the drug pump injection15min(T1)decreased significantly compared with T0(P <0.05).In test group, MBPand RR was not statistically significant when compared with T0(P>0.05);Ramsay score in DM and DH group were higher than C group (P <0.05),and Ramsay score in DH group was higher than DM group (P<0.05).Postanaesthetic shivering was seen in7patients in groupC(23.3%),5patients in group DL(16.7%),and2patients in groupDM(6.7%).There were4patients with dry mouth.All without nausea orvomiting,and the same as bradycardia and respiratory depression.Conclusion:0.4ug/kg dexmedetomidine intravenous pump injection15min post spinal and epidural anesthesia was able to effectively reducethe incidence and severity of shivering, without adverse drug reactions.