Avian and Exotic Animal AnesthesiaJavier G Nevarez [email protected]
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
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!!!