Article Artikel Severe hypoxaemia in fieldanaesthetis - PDF document

Article — Artikel, J PRaathand LKleinSafeandreliableanaesthesiaofrhinocerosisanimportanttoolforhealthcareofbothcaptiveandfree-ranginganimalsandforconservation-basedprogrammes.Physiologicalmonitoringofwhiterhinocerosanaesthetisedwithetorphinehydrochloride(M99)revealsphysiologicalalterations,includinghypertension,tachycardia,acidaemiaandrespiratorydepressionwithhypoxiaandhyper.TheadditionofazaperonetoM99decreasedbloodpressureinaseriesof6animals.Manyreportsrecommendoxygen(O a ,indicatingamildtomoderatemetabolicacidosis.Therhinoceroswerealsohypertensive(systolicbloodpressure=21.861±5.465kPa(164±41mmHg))andtachycardic(HR=107±31/min).Followingnasaltrachealintubationandinsufflation,the%OandPincreasedwhilebloodpHandPremainedunchanged.Trachealintubationviathenoseisnotdifficult,andwhenoxygenisinsufflated,theP blindfoldedandearplugswereinsertedToensurethesafetyoftherhinocerosduringthisstudy,20–50mgnalorphine(Lethidrone,Wellcome)and/or100–400mgDoxapramHCL(Dopram-V,FortDodgeAnimalHealth,FortDodge,Iowa50501USA)wereadministeredintravenously(i.v.),atthediscretionoftheveterinarianincharge(JPRorDG)toreverseapnoeabothbeforeandduringthedata-Arterialbloodgases(ABG)werecollectedfollowingcatheterisationoftheauriculararterylocatedontheinsideofthepinna,usinga22gaugecatheter(Jelco,Critikon,SA,JohnsonandJohnson(Pty)Ltd.SA).Thesampleswerecollectedanaerobicallyintoheparinisedsyringes,whichweresealedandstoredoniceuntilanalysedwithin3hoursofcollection.Thecatheterwasmaintainedwithaheparinsalineflushand1–2m ofbloodwaswithdrawnanddiscardedpriortocollectionoftheABGsample.Arterialhaemoglobinoxygensaturation(%O)andbaseexcess(BE)werecalculatedaccordingtostandardhumanformulae.SampleswerecollectedpriortoadministrationofOandatvariousintervalsduringOistration.Samplesfromcontrolanimals(4fromtheKrugerParkand3fromMpumalangaParks)werealsocollectedatvariousintervalsduringthemonitoringTrachealintubationwasaccomplishedwithanequinenasogastrictube(0.9or1.4cminternaldiameter)(KalayjianIndustries,Inc,LongBeach,CA90806,USA)passedalongtheventralfloorofthenasalcavitytoavoidthenasalturbinates.Oncethetubewasintheposteriorpharynx,theoperatorlistenedforanexhalationandthenadvancedthetubeintothetracheatoapproximatelythelevelofthetrachealbifurcation(Fig.1).Thetubeneverenteredtheoesophagusduringthisstudy,butonoccasionwasreflectedbytheposteriorpharyngealwallandcameouttheothernostril.Trachealintubationwasverifiedbylisteningtotheairpassingthroughthetubeduringrespiration.Oxygenwasadministeredatarateof15–30 /mindependingonthesizeofThedata-gatheringperiodvariedamonganimalssinceitwasrelatedtothetimerequiredtocrateeachanimal.When2animalswereanaesthetisedsimulta-neously,1animalwaschosentobecratedlast,thusobtainingalongermonitoringperiod.Thecontrolanimalswereselectedrandomly.Systolicbloodpressurewasmeasuredindirectlyfromthetail(Dinamap,CritikonInc.Tampa,Florida33607USA).Respirationratewasobtainedbyfeelingtheexpirationofairandaheartratewasobtainedusingastethoscope.RectaltemperaturewastakentocalibratetheFollowingthemonitoringperiodintheKrugerParkrhinoceros,M99effectswereantagonisedwitheither6–7.5mgdiprenorphine(M50-50,C-Vet)or25–40mgnalorphinei.v.andeachanimalwasdirectedtothecrateusingthepre-placedropesafteritregaineditsfeet.In10rhinocerositwaspossibletoobtainanABGsamplefromthearterialcatheterintheauriculararteryaftertheanimalwasstandinginthecrate.The3controlrhinocerosfromMpumalangaweregiven40–80mgnaltrexonei.v.andallowedtorecover and return to their habitat.RESULTSNomortalityorpost-anaestheticmor-bidityoccurredintherhinocerosthatTheresultsofphysiologicalmonitoringofrhinocerosthatreceivedOmentationandthecontrolsaresummarisedinTable1.Physiologicaldatawerenotrecordedforallanimalsstudied.NotethatthemeansofallABGparametersexceptthePandthe%Oaresimilarinthegroups.Bothgroupsshowedrespi-ratoryandmetabolicacidosis,hypercapnia,tachycardia,decreasedrespiratory rate and moderate hypertension.ThesummaryofallABGsamplescollectedoverthemonitoringperioddividedintothegroupthatreceivedOsupplementationandthenon-supple Fig.1:Drawingofarecumbentrhinocerosshowingtheplacementofthenasotrachealtubepassingthroughthelarynxintothetrachea,withthetubeattachedtoanoxygentankwithaflow.Table1:SummaryofthephysiologicalmonitoringandarterialbloodgasvaluesfrombothO-supplementedandcontrolanimals.Meanvaluesforallparameters(exceptPand%O,whichincreasedmarkedlyinthesupplementedanimals)arecomparableandshow BEHeart rateRespiration rateSystolic BP( %)(kPa)(kPa)(mmol/ (mmol/ )(per min)(per min)(kPa)Suppl.Mean887.14813.8639.46423.5–5.8104924.93SD150.0978.2652.6664.24.43837.7338393939393915131.47Mean577.2065.0658.66523.7–3.71061024.93SD180.0781.4661.6004.85.03233.20 3636363632367101.07 mentedcontrolgroupareshowninTable2.Time0showsvaluesobtainedfromthe1stABGsamplecollectedinbothgroups,andservesasabaselineforboththecontrolanimalsandtheanimalsthatreceivedOfollowingTime0.ThePandthe%OvaluesincreasedrapidlyandmarkedlyfollowingOsupple-mentationwhiletherhinocerosthatdidnotreceiveOremainedveryhypoxae-micthroughoutthemonitoringperiod,withonlyaslightelevationat30min.TheverylowPvalues,combinedwithacidosis,resultedinseverehaemoglobindesaturationwithinitial%Obelow50%recordedinthe7controlanimalsbreathingambientair,whileduringOsupplementation,30of39samplesshowedthe%Otobegreaterthan90 %andinonly1samplewas%Obelow80%.ThepHandPinbothgroupsshowedconsistentacidaemiaandhypercapnoeathroughoutthemonitoringperiod.Baseexcessremainedbelow0mmol/ exceptforthe20–25minmonitoringperiodinthenon-supplementedrhinoceros(0.3mmol/ ),indicatingthatmetabolicacidosispersistedthroughouttherecumbentperiod.Themeanbicarbonatevalueintheanaesthetisedrhinocerosrangedbetween22and28mmol/ (Table2),reflectingthedecreaseduetometabolicacidosis,combinedwiththeincreaseresultingfromhypercapnoeaduetoanaesthetic-inducedrespiratoryArterialbloodgasvaluesfrom2subadultfemalerhinocerosinthisstudyduringthemonitoringperiodandinitialrecoveryareshowninFig.2(anOplementedanimal)andFig.3(acontrolanimal)withthePandthe%OplottedandtheotherABGvalueslistedinthetablebelowthechart.Figure2plotsPand%OandP,beforeandduringOsupplementation.Theand%OincreasedrapidlyduringsupplementationwhilethePmainedelevated.TheABGvaluesfromthestandinganimalfollowingthereversalbyM99showedadropinbothPandPwhilethepHandBEincreased,indicatingapartialcorrectionofboththerespiratoryandthemetabolicacidosis.Figure3showsthat,inthenon-Oplementedanimal,hypoxiaandhypercapnoeapersisteduntiltheanimalwasstandingafterreversal.Bothanimalswerealsoacidoticduringrecumbency,withtheABGvaluesreturningtowardsnormalbythetimetheanimalswereFigure4showstheinitialeffectofOTable2:SummaryofthearterialbloodgasvaluesduringthemonitoringperiodfromO-supplementedandcontrolanimals.Time0combinestheinitialsampleonthesupplementedanimalsandcontrolanimals.FollowingtheoxygensupplementationtheriseinP Time 0OsupplementationNo O First 10 min11–20 min20–40 minFirst 10 min11–20 min20–35 minpHaMean7.1757.1337.1427.2137.2467.2447.246SD0.0760.1140.0820.0360.0510.0840.067(%)Mean49848995626970SD161715323138(kPa)Mean4.66612.79715.33013.5974.9325.4655.599SD1.2007.86510.1313.3331.8661.6000.933(kPa)Mean8.2659.7319.7318.3989.3318.5318.931SD1.6003.3332.2660.5330.9331.2002.000 )Mean22232425282427SD4542533 )Mean–6.4–6.77–5.7–3.2–0.26–1.40.3SD4.275.33.41.93.495.732.7Sample time (min)Mean71528101724SD3370.133 2119146555 ChartandassociatedtableshowingtheresultsofarterialbloodgasvaluesofasubadultfemalerhinocerosthatreceivedOsupplementationviaanasotrachealtube.NotetherapidinitialriseofboththePand%Ooncesupplementationbegan.Whentheanimalwasstandinginthecratethearterialbloodgasvaluesstartedtoreturntowardsnormality. supplementationonanadultrhinoceros.TheOsupplementationwasdiscontin-uedfor4minat14minwitharesultantdecreaseofbothPand%O,whichincreasedrapidlyagainonceOmentationwasresumed.ThisillustratestherapidchangesthatoccurintheABGAcommonprocedureistheadministra-tionofnalorphine(10–30mg)i.v.towhiterhinoceroswithin10minofrecum-bency.Theobjectiveistoimprovethesafetyoftheprocedurebylighteningtheopioidanaesthesiaandimprovingrespi-ration,whichisobservedclinically.Twelveanimalsthatreceivednalorphineweremonitored.Follow-updata,within10minofinjection,showedverylittleimprovementinthephysiologicalparam-eterscomparedtothe5controlanimalsthatdidnotreceivenalorphineorOsupplementation(Table3).Themajorphysiologicalalterationspersisted.Whennalorphinewasgiventhenetchangein,afteranaverageof7minutes,wasanincreaseof0.93kPa(7mmHg)from4.27 to 5.20 kPa (32 to 39 mm Hg).Table4showstheABGvaluesof10rhinoceros,includingtheanimalsinFigs2and3,sampledatvarioustimeswhentheywerestandingintheircratesafterhavingreceivedtheantagonisttoM99.TheABGvaluesreturnedtowardsnormalwithinanaverageofabout3minThisstudydocuments5observations:1)rhinocerosanaesthetisedwithdosesofM99andazaperoneappropriateforfree-rangingconditionsexperiencesevererespiratorydepressionandhypoxaemia,moderatehypercapnia,andcombinedrespiratoryandmetabolicacidosis.2)Tenrhinocerosrequiredadministrationofnalorphinewithinthefirst10mintoensuretheirsafety,whiletheresultantmonitoringwithin10minofadministrationshowedlittlephysiologicalimprovement.3)Healthyrhinoceroscantoleratetheseseverephysiologicalalterationsforshortperiodsduringfieldanaesthesiawiththeseagents.4)TrachealintubationandinsufflationwillrapidlyandmarkedlyimproveoxygenationasshownbyPandthe%O,butdoesnotaffecthypercapnoeaormetabolicacidosis.5)FollowingantagonismofM99andtheendofrecumbencytheABGvaluesrap-idly return towards normal levels.Therespiratorydepressionandresultanthypoxiaisprobablydueto4factors:1)thehighdoseofM99requiredtoshortentheinductiontimewhenanaesthetisingananimalunderfieldconditions;2)whiterhinocerosareverysensitivetoopioidssuchasM99;3)alargeanimalrecumbentwhileanaesthetisedissubjecttophysiologicalalterationsthatleadtocardiopulmonarydepression,ashasbeenshownindomesticanimalsandhumans;4)alargerecumbentanimalwilldevelopaperfusion/Therealsoseemstobevariationbetweenwhiteandblackrhinoceroses,withtheformerbeingmuchmoresensitivetotherespiratorydepressanteffectsofInthegroupofwhiterhinocerosunderstudy,thenegativeBEvaluesindicatesomedegreeofmetabolicacidosis.FormulaeusedintheinstrumentsoftwareforthecalculationofBEarebasedontherelationshipofpHtoPinhumans,withthe‘normal’rangeforBEcentredaroundavalueof0mmol/ .Usingtheseformulae,normaldomesticherbivorestypicallyhaveBEvaluesabove0,from+4to+8mmol/ ,dependingonthespecific Fig.3:ChartandassociatedtableshowingtheresultsofarterialbloodgasvaluesofasubadultfemalerhinoceroscontrolthatdidnotreceiveOsupplementation.NotehypoxiawithlowPand%OandhypercapniawithelevatedP,whichpersisteduntilthe Fig.4:ChartandassociatedtableshowingtheresultsofarterialbloodgasvaluesofanadultfemalerhinocerosthatinitiallyreceivedOsupplementation.Thesupplementationwasdiscontinuedfor4minuteswithamarkeddropinboththePand%O,which bloodgasanalyser(LK,pers.obs.,2003).Althoughnormalvaluesforunrestrained,free-rangingwhiterhinocerosarenotavailable,itislikelythattheiracid-basebalanceissimilartootherherbivoresandthatthenegativeBEvaluesreportedhererepresentatruemetabolicacidosis.Metabolicacidosisintheseanimalsprobablyresultedfromlacticacidaccumulationduetomuscleactivitybeforeandafterdarting,andhypoxaemiaduringtherecumbentperiod.ThepersistenceofmetabolicacidosiseveninthoseanimalsthatreceivedOsupplementationmaybeduetothemuscleactivityandrigidity,whichtypicallyaccompaniesrestraintArterialhaemoglobinoxygensaturationvaluesintheserhinoceroswerecalculated,alsousingformulaebasedontheOaffinityandBohreffect(effectofachangeinpHontheP50(Patwhichthehaemoglobinishalf-saturatedwith))ofnormaladulthumanhaemoglobin.DomestichorseshaveaP50of3.33kPa(25mmHg),similartohumansandthereforethe%Ovaluescalculatedfromhumanformulaearereasonablyaccurate.Noreportsofrespiratorycharacteristicsofwhiterhinoceroshaemoglobinusingwholebloodcouldbefoundintheliterature,butresultsof1studyoftheeffectsofvariousanionsandotherfactorsontheOaffinityofwhiterhinoceroshaemoglobininsolutionsuggestedthattheP50mightbe2.67kPa(20mm Hg).Ifthisisthecase,thenthetrue%Ointherhinocerosinthisstudymaybesomewhathigherthanthevaluesreportedherealthoughstillprofoundlydesaturatedinthoseanimalsdidnotre-Nasaltrachealintubationisnotadifficultprocedureinthefield.TheinsufflationwithOimprovesthesafetyoftheprocedurebyincreasingthePthe%O,butdoesnotcorrecttheacidosisorhypercapnia,whichhasalsobeenreportedinwapiti.GivingOdoesnotseemtoworsentherespiratorydepressionbyremovinghypoxicrespiratorydrive,sincesignificantincreasesinPwerenotdetectedduringOmentation.Caremustbetaken,wheninsufflatingoxygenthoughanasotrachealtubeorcatheter,toensurethatthetubeisinthetrachea,andnottheoesophagus.Insufflationofoxygenintotheoesophaguscanresultingastricrupture,whichhasoccurredinhorses(LK,pers.obs.,2003),butinthisstudywedidnotpassthetubeintotheprobablythankstopharyngealMethodstocorrecttheacidosisandhypercapnoeawouldincludeIPPV,whichwouldbedifficultinthefield,sinceitwouldrequireplacementofacuffedendotrachealtubeandalarge-capacityventilator,or2demandvalvesjoinedinparallelwithalargersourceofcom-pressedOthanrequiredforinsufflationasusedinthisstudy.EvenwithIPPVinlargespecies,hypoxiamaypersistinsomeindividualsduetoventilation/perfusiondisparity,andhypercapnoeapersistsbecauseofinsufficienttidalandminuteWeacknowledgethecooperationandlogisticalsupportgivenbytheSouthAfricanNationalParksandMpumalangaParksBoard.WealsoacknowledgethegeneroussupportofBritishAirways,FriendsoftheNationalZoo(FONZ)andtheShirleySichelFund.TheauthorsalsothankJJvanAltena,JohanMalanandMariusKrugerfortechnicalsupportwithaspecialthankstothehelicopterpilotsoftheKrugerNationalParkwhoseskillandeffort helped make this study possible.1.BaumannR,MazurG,BraunitzerG1984Oxygenbindingpropertiesofhemoglobinfromthewhiterhinoceros(-GLU)andthe tapir.RespirationPhysiology2.Cornick-SeahornJL,MikotaSK,SchaefferDO,RanglackGS,BoatrightSB.1995Isofluraneanesthesiainarhinoceros.JournalofAmericanVeterinaryMedicalAssociationTable3:Effectofreceivingnalorphinein12rhinoceroscomparedto5animalsthatdidnotreceivenalorphineorOsupplementation.Note RespirationHeart rateP(per min)(per min)(kPa)(kPa)(%) Time:T = 010 minT = 010 minT = 010 minT = 010 minT = 010 min12 Nalorphine10101381159.609.604.675.477175 5Controls911113879.209.205.205.207479 Table4:Arterialbloodgasvaluesfrom10rhinoceroswhiletheywerestandinginacrateafterreversalofM99.Notethatallvaluesare Arterial samples Total time downSample after upS(min)(min)(%)(kPa)(kPa)(mmol/ )(mmol/ 121877.2798.2657.87826.9–0.34912827.2387.5988.22525.4–2.5211907.2669.4648.34527.61.0217907.2709.4648.47828.30.3414867.3167.7317.55828.21.2601917.3159.0646.57225.4–0.8413827.3046.9326.23823.5–2.6353767.3065.9996.09223.0–2.9261887.2928.5318.13128.70.8291927.3409.9987.50529.72.9 Mean33.53.486.57.2938.2917.50526.7–0.3SD14.63.65.10.0301.2530.8932.31.91=1010101010101010 3.DunlopCI,HodgsonDS,CambreRC,KennyDE,MartinHD1994CardiopulmonaryeffectsofthreeprolongedperiodsofisofluraneanesthesiainanadultJournalofAmericanVeterinaryMedicalAssociation4.HeardDJ,JacobsonER,BrockKA1986EffectsofoxygensupplementationonbloodgasvaluesinchemicallyrestrainedjuvenileAfricanelephants.JournaloftheAmericanVeterinaryMedicalAssociation5.HeardDJ,OlsenJH,StoverJ1992Cardiopulmonarychangesassociatedwithchemicalimmobilizationandrecumbencyinawhiterhinoceros(CeratoheriumsimumJournalofZooandWildlifeMedicine6.HattinghJ,KnoxCM,RaathJP1994Arterialbloodpressureandbloodgascompositionofwhiterhinocerosesunderetorphineanaesthesia.SouthAfricanJournalofWildlifeResearch7.KockMD,MorkelP,AtkinsonM,FogginC1995Chemicalimmobilizationoffree-rangingwhiterhinoceros(simumsimum)inHwangeandMatoboNationalParks,Zimbabwe,usingcombinationsofetorphine(M99),fentanyl,xylazine,anddetomidine.JournalofZooandWildlife8.LeBlancPH,EickerSW,CurtisM,BeehlerB1987Hypertensionfollowingetorphineanaesthesiainarhinoceros(Dicerossimus).JournalofZooandWildlifeMedicine9.McDonellW1996RespiratorySystem.InThurmonJC,TranquilliWJ,BensonGJLumbandJones’veterinaryanesthesia.Williams & Wilkins, Baltimore: 115–14710.PaoloP,CrociM.RavaganI,TrediciS,PedotoA,LissoniA,GattinoniL1988Theeffectsofbodymassonlungvolume,respiratorymechanics,andgasexchangeduringgeneralanesthesia.Anesthesiaand11.QuandtJE,RobinsonEP1996Nasotrachealintubationincalves.JournaloftheAmericanVeterinaryMedicalAssociation12.RaathJP1999Anesthesiaofwhiterhinoceroses.InFowlerME,MillerRE(eds)Zooandwildlifemedicinecurrenttherapy4.13.ReadMR,CaulkettNA,SymingtonA,yTK2001Treatmentofhypoxemiaduringxylazine-tiletamine-zolazepanimmobilizationofwapiti.CanadianVeterinaryJournal14.RieboldTW,EngelHN,GrubbTL,AdamsJG,HuberMJ,SchmotzerWB1994OrotrachealandnasotrachealintubationinJournaloftheAmericanVeterinaryMedicalAssociation15.RogersPS1993Chemicalcaptureofthewhiterhinoceros(Ceratotheriumsimum).InMcKenzieAA(ed.)ThecaptureandcaremanWildlifeDecisionSupportServiceandSouthAfricanVeterinaryFoundation,Pretoria, South Africa: 512–52816.SomaLR1980Equineanesthesia:causesforreducedoxygenandincreasedcarbondioxidetensions.CompendiumofContinuingLargeAnimalSupplement17.WebbAI1984Nasalintubationinthefoal.JournaloftheAmericanVeterinaryMedical