Intrathecal Dexmedetomidine Can Decreases The ED95 Of Bupivacaine In Spinal Anesthesia For Ceasarean Section

Background:Spinal aneasthesia was established to be an ideal choice for ceasarean section,when there were not any contradictions for this local aneasthesia technique.Hypotension,which is closely related to maternal and neonatal morbidity and mortality,was the most common side effect of spinal aneasthesia.To reduce the high incidence of hypotension,many investigators recommended using intrathecal low-dose of local anesthetics and combined with epidural anesthesia as a back-up.However,shortcoming associated with this technology was the relatively short duration of pain relief.Therefore,diverse intrathecal adjuvant were studied and practiced in clinical aneasthesia,such as opioids,clonidine,neostigmine,epinephrine,and magnesium sulfate,in order to reduce the dose of intrathecal local anesthetics and expect to prolong the period of analgesia.Opioids(fentanyl,sufentanil)which are usually utilized with subarachnoid local anesthetics,are accompanied by a large amount of undesirable side-effects,such as delayed respiratory depression,urinary retention,and pruritus.Clonidine,neostigmine and epinephrine,also exhibit adverse effects such as sedation and so on.Magnesium sulfate could prolong the duration of spinal analgesia,but fail to reduce the dose requirement of intrathecal bupivacaine in our previous study.Dexmedetomidine(Dex),an a2 receptor agonist,with a2/al selectivity 8 times than that of clonidine has the potential to enhance the quality of central and peripheral anesthesia when adding to local anesthetics as an adjuvant.No previous studies have assessed whether the addition of intrathecal Dex can reduce the dose requirement of intrathecal local anesthetics for spinal anesthesia in ceasarean section.We therefore designed the present prospective,randomized,double blinded study to investigate the hypothesis that intrathecal 5 mcg of Dex would decrease the 95%effective dose(ED95)of intrathecal hyperbaric bupivacaine in spinal anesthesia for ceasarean section using an improved up-down sequential allocation method.Objective:To investigate the hypothesis that intrathecal Dex would decrease the 95%effective dose(ED95)of intrathecal hyperbaric bupivacaine in spinal anesthesia.Methods:Ninety patients scheduled for ceasarean section were randomly divided into two groups(45 patients in each).All patients in the two groups received spinal anesthesia.The mixed local anesthetic contains different dose of bupivacaine and 10%dextrose 1mL which was diluted into 3 mL with sodium chloride injection.The patients in trial group received bupivacaine + dexmedetomidine,and the patients in control group received bupivacaine only.The sufentanil patient controlled intravenous analgesia was used for all patients post-operation.The clinical trial was accomplished using an improved up-down sequential allocation method.The first patient in each group received bupivacaine 4 mg.And the next dose for following patient was determined by the probability of successful anesthesia of the previous neighboring dose.The ED95 and its 95%confidence interval(95%CI)of bupivacaine in spinal anesthesia for ceasarean delivery were calculated by using Probit regression method.Characteristic of spinal anesthesia,the effect of analgesia and adverse reactions were observed.ResultsThe ED95 of bupivacaine in spinal anesthesia for ceasarean delivery was 10.9mg(95%CI:4.4?56.8 mg)and 7.4mg(95%CI:5.6-12.4 mg)respectively with significant difference between two groups(P<0.05).The duration of sensory block was longer in the trial group than that in the control group((110.3±35.3)min vs.(67.5±26.2)min,P<0.05).The duration of analgesia was longer in the trial group than that in the control group((224.9±45.4)min vs.(155.1±31.6)min,P<0.05).The consumption of postoperative rescued sufentanil was significantly lower in the trial group than that in the control group((56.6±9.8)?g vs.(64.8±11.8)?g,P<0.05).No serious adverse reactions occurred in both groups.ConclusionIntrathecal dexmedetomidine 5 ?g can potentiate bupivacaine antinociception by 33%in spinal anesthesia for patients undergoing cesarean section.