Avian and Exotic Animal AnesthesiaJavier G Nevarez DVMjnevarez@vetmed.lsu.edu

ObjectivesKnow the avian respiratory anatomyAir sacs Know the avian breathing cycleKnow the respiratory stimuli for birds and reptilesKnow how methods for thermoregulation during anesthesiaKnow how to monitor birds and reptiles during anesthesia

Avian Respiratory AnatomyNo diaphragmRely on movement of keel boneComplete tracheal ringsDo not inflate ET tube cuffSyrinxNo epiglottisocw.tufts.edu/Content/5/lecturenotes/215768

Avian Respiratory AnatomyPneumatic BonesHumerus, clavicle, keel, ribs, +/- femurNon expandable lungsAttached to ribs and dorsal body wall

Air SacsCranial air sacsInterclavicular (1)Cervical (2)Cranial thoracic (2)Caudal Air SacsCaudal thoracic (2)Abdominal (2)

http://www.paulnoll.com/Oregon/Birds/Avian-Respiratory-2.html

Breathing Cycle1st InspirationTrachea Bronchi Cd. Air sacs1st ExpirationCd. Air sacs Lungs2nd InspirationLungs Cr. Air sacs2nd ExpirationCr. Air sacs Bronchi Trachea

http://www.faculty.biol.ttu.edu/schmidt/web_site/ORNITH%20avian%20physiology.htm

Inspiration

Expiration

Ventilation MechanicsInspirationSternum: cranio-ventralRibs: cranialIncreases volume of coelomic cavityAllows air sac expansion

Ventilation MechanicsExpirationSternum: caudo-dorsalRibs: caudalDecrease volume of coelomic cavityCompresses air sacs

Gas ExchangeCounter current mechanismSimple diffusion of O2 and CO2Parabronchi (3o bronchi)CapillariesBreathing stimulusO2 and CO2

http://sps.k12.ar.us/massengale/bird_notes_bi.htm

Reptile Respiratory AnatomyNo diaphragmRely on rib/coelomic expansionComplete tracheal ringschelonians and crocodilians Incomplete tracheal ringslizards and snakesNo epiglottis

Reptile LungsVaried anatomySpongy mammal-likeThin air sac-likeIntermediate/combinationSnakesMost only have right lungBoids may have two Expandable

Gas ExchangeCounter current mechanismSimple diffusion of O2 and CO2Breathing stimulusO2

Indications for AnesthesiaRadiographsSurgeryBiopsyPhysical exam

Anesthetic AgentsInjectableUsed less frequently in birds

InhalantsUsed routinely for induction in birdsUsed for maintenance in other species

Pain ManagementOpioidsButorphanolNSAIDSMeloxicam (Metacam), Carpofen (Rimadyl)Local/topicallidocaine

EquipmentAnesthetic machineAnesthetic masksET tubes2.0 6.0 i.d.Non-cuffed and cuffed14g 16g IV cathetersPaper clip/hemostats as speculum

EquipmentHeat sourceHeating padsHeat lampsForced-air warmersWarm fluid bagsRice/bean bags

EquipmentIV catheters 26g 22gEmergency drugsIV/SQ fluidsMonitoringDopplerTemperature probeECGEtc.Incubators

IV AccessBirdsJugular veinUlnar veinMedial tarsometatarsal veinReptilesJugular veinVentral coccygeal veinVentral abdominal veinSub-carapacial

IO AccessBirdsUse non-pneumatic bones only!!UlnaTibiotarsusReptilesFemurTibiaCarapace/plastronIO access can be used the same as IV but with slower volume of infusion

Pre-medication - birdsOpioids Respiratory depression??Give 30min to 1 hr before anesthesiaNSAIDSDiazepam

Pre-medication/induction -reptilesOpioidsNSAIDSKetamineMedetomidineTelazolPropofol

Induction - birdsIsoflurane/sevofluraneMask downStart at 5% with 1L/min O2Asses depthFlaccid wings and legsEyes closedHR/RRRighting reflex

MaintenanceIsoflurane0.5% - 2%500ml 1L/min O2IPPVDO NOT EXCEED 15 20mmHgPOP-OFF valve MUST REMAIN OPEN after breathing6 12 breaths/min

Determining plane of anesthesiaReflexesRighting reflexCorneal reflexTongue withdrawalToe pinch

MonitoringStethoscopeReflexesDopplerTemperature probeECGPulse oximeterCapnograph

Monitoring BirdsHeart Rate> 100 bpm is normal< 100 bpm is of concernRespiratory Rate6 12 bpm during anesthesiaIPPV if shallow or inconsistentTemperatureBirds: 105oF is normal

Monitoring Reptiles (NEW SLIDE)Heart RateVaries with species, temperature30-60 bpm is normal

HypothermiaHeat lossConvectionAir exchange at body surfaceRadiationHeat loss to surfaces and environmentConductionHeat loss from contact (i.e. cold table)EvaporationHeat loss from lungs, skin, exposed tissues

Preventing HypothermiaForced-air warmersCan reduce convection, conduction, and radiation losses depending on the blanket typeHeating padsReduce conduction lossesHeat lampsReduce radiation lossesWater bathReduce conduction, radiation lossesBean/rice stockingsReduce radiation losses

Preventing Hypothermia

RecoveryWean off gas before the end of procedureMaintain O2 at low flow rateKEEP WARM!!!!!!!!!!!!!!!!Breathing stimulusBirds: CO2 and O2Reptiles: O2

If you run into problems, turn off the inhalant anesthetic and proceed to treat the patientWhat can go wrong?HypothermiaRespiratory arrestCardiac arrestdeathHow to fix/prevent it?Have heat sourceIPPV, doxapramAtropine, epi., CPRBE PREPARED!!!!

Why do things go wrong?LACK of PREPARATION!!!!!Lack of monitoringPatient kept too deepIPPV not provided on timeUnderlying diseaseUnknown physiological reasons

Challenging speciesWaterfowlProne to bradychardiaBudgies and CockatielsHypothermiaCritical recovery periodEagles and large birdsExcitatory phase during inductionBradychardiaMay require higher % for maintenance

Challenging SpeciesReptilesUsually require IPPVUnpredictable anesthesiaDifficult to maintain plane of anesthesia

ConclusionUnderstand anatomy and physiology in order to design anesthetic plan and emergency responsesPerform active, aggressive monitoringProper thermoregulation is essentialBe prepared!!!