Influence Of Different Body Mass Index On Dexmedetomidine Assisted Spinal Anesthesia In Elderly Patients

Objective:To study on the effect of different body mass index on demetomidine-assisted spinal canal anesthesia in elderly patientsMethods:Determination of half effective dose of dexmetomidine in patients with different body mass index by sequential method during lower limb fracture surgery in elderly patients.Select 45 cases of elderly patients undergoing surgical treatment of lower extremity fractures in our hospital from January 2017 to December 2017.All of the patients are aged 65 to 80,whose ASA gradeII or III level,No contraindications of intraspinal anesthesia.Patients are divided into 3 groups according to BMI:I group BMI?18.5kg/m²,II group BMI 18.5²4kg/m²,III groupBMI?24kg/m².All of the patients are not administered with premedication during pre-operative period and following steps are initiated after patients entering operating room,including establishing upper intravenous pathway,infusing Sodium Lactate Ringer's Injection,conventional mask oxygen inhalation,monitoring vital signs of BP,HR,SpO2,RR and other index such as BIS.Combined spinal and epidural anesthesia are performed at L3-4 intervertebral space by using local anesthesia fluid 0.75%bupivacaine 2 ml+10%glucose 1ml,fixing anesthesia level in T9-T11.When anesthetic effects are satisfied,patients of 3groups are pumped with dexmedetomidine according to same loading dose0.5ug·kg^-1,achieved in 15 minutes.Subsequently,the patients in each group were pumped by the sequential method:The current rate of pump injection,According to dexmedetomidine injection dose of the previous patient.Ramsay<3score as negative,The current patient increases the pump speed.Ramsay>3score as positive,The current patient decreases the pump speed Strat at 0.03ug·kg^-1·h^-1and adjacent dose gradient is set as0.05ug·kg^-1·h^-1.Calculate ED₅₀0 and relevant 95%confidence interval of dexmedetomidine of 3 groups patients by using probability unit regression analysis method.Observe and record BP,HR,RR,SpO2 and BIS value of 3groups patients at four times points,including at the time of just entering operation room?T1?,completion of dexmedetomidine loading injection,30minutes after infusion of maintenance dose and end of operation.Meanwhile,observe and record occurrence of adverse effects during operation,such as hypotension,bradycardia,respiratory inhibition,etc.Result:1.comparison among groups:there is no statistical significances in the comparing difference of MAP,HR,RR,SpO2,BIS values at any time point in3 groups?P>0.05?.2.Comparison within groups:there is no statistical significance in the comparing difference of RR,SpO2 value between T2-4 and T1 in 3 groups?P>0.05?.all the MAP,HR,BIS value of T2-4 are markedly lower than T1in 3 groups,showing a statistical difference.3.Dexmedetomidine ED₅₀0 and 95%confidence interval of 3 groups patients measured by sequential method are:I group:ED₅₀0 is 0.32ug·kg^-1·h^-1(95%CI 0.30-0.34·kg^-1·h^-1)II group:ED₅₀0 is 0.26ugkg^-1·h^-1(95%CI0.24-0.28·kg^-1·h^-1)III group:ED₅₀0 is 0.19ug·kg^-1·h^-1(95%CI0.18-0.21kg^-1·h^-1)The three groups were statistically different?P<0.05?,Table 9Conclusion:The ED₅₀0 of dexmetomidine in patients with different body mass index?BMI?was different when the operation of lower extremity with intraspinal anesthesia.