SpinalCordBloodFlowChangebyIntravenousMidazolam

DuringIsofluraneAnesthesia

TomokiNishiyama,MD,PhDByCorallibraBackgroundMidazolamhasbeenusedforgeneralanesthesiaandsedationduringlocalanesthesiaorartificialventilation.IthasbecomeclearthatmidazolamhasananalgesicpropertymediatedbyGABAreceptorsinthespinalcord.Therefore,itisimportanttoknowtheeffectsofmidazolamonspinalcordbloodflow.Methods32Cats(male;2.5-3.5Kg;12h)Isoflurane(4%)in100%oxygenIsoflurane(1%)in40%oxygenEnd-tidalcarbondioxidetensionBetween30and40mmHganesthesiamaintainventilationMethodsMonitor,Mesured5,15,30,60,90,120minmidazolam0,1,2,or4mg/KgHeartrateArterialbloodgasanalysisTemperature37.0℃±0.5℃Midlineskinincision,L1-5wereremoved,andthespinalcordwasexposed.Aplatinumwasinsertedstereotaxicallyintothespinalcordtoadepthof1mmat2mmlateraltothemidlineatL2.Spinalcordbloodflowwasmeasuredeiththehydrogenclearancemethod.Statisticalanalysiswasperformedwithrepeated-measuresanalysisofvarianceResultsArterialbloodgasvaluesbeforethestudydrugtreatmentwithoutanydifference.Arterialbloodpressuredecreasedduringthefirst30minafterMID2and4mg/KgHeartratedidnotchange.ResultsSpinalcordbloodflowincreasedsignificantlyfor90minafterMID1mg/Kgandfor15minafterMID2mg/Kg.DiscussionDiscussionDiscussionHowever,inpatients,midazolamisoftencoadministeredwithotheranestheticsToknowtheeffectsofmidazolam,isofluraneshouldbediscontinuedConclusionAsmallerdoseofmidazolam(1mg/kg)increasedspinalcordbloodflowwithoutchangesinarterialbloodpressure,butalargerdose(4mg/kg)didnotchangespinalcordbloodflowThiswasassociatedwi