(2) avian and exotic animal anesthesia
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Objectives Know the avian respiratory anatomy
Air sacs Know the avian breathing cycle Know the respiratory stimuli for birds and
reptiles Know how methods for thermoregulation
during anesthesia Know how to monitor birds and reptiles
during anesthesia
Avian Respiratory Anatomy No diaphragm
Rely on movement of keel bone Complete tracheal rings
Do not inflate ET tube cuff Syrinx No epiglottis
ocw.tufts.edu/Content/5/lecturenotes/215768
Avian Respiratory Anatomy Pneumatic Bones
Humerus, clavicle, keel, ribs, +/- femur Non expandable lungs
Attached to ribs and dorsal body wall
Air Sacs Cranial air sacs
Interclavicular (1) Cervical (2) Cranial thoracic (2)
Caudal Air Sacs Caudal thoracic (2) Abdominal (2)
http://www.paulnoll.com/Oregon/Birds/Avian-Respiratory-2.html
Breathing Cycle 1st Inspiration
Trachea → Bronchi → Cd. Air sacs 1st Expiration
Cd. Air sacs → Lungs 2nd Inspiration
Lungs → Cr. Air sacs 2nd Expiration
Cr. Air sacs → Bronchi → Trachea
http://www.faculty.biol.ttu.edu/schmidt/web_site/ORNITH%20avian%20physiology.htm
Inspiration
Expiration
Ventilation Mechanics Inspiration
Sternum: cranio-ventral Ribs: cranial Increases volume of coelomic cavity Allows air sac expansion
Ventilation Mechanics Expiration
Sternum: caudo-dorsal Ribs: caudal Decrease volume of coelomic cavity Compresses air sacs
Gas Exchange Counter current mechanism
Simple diffusion of O2 and CO2
Parabronchi (3o bronchi) Capillaries
Breathing stimulus O2 and CO2
http://sps.k12.ar.us/massengale/bird_notes_bi.htm
Reptile Respiratory Anatomy No diaphragm
Rely on rib/coelomic expansion Complete tracheal rings
chelonians and crocodilians Incomplete tracheal rings
lizards and snakes No epiglottis
Reptile Lungs Varied anatomy
Spongy mammal-like Thin air sac-like Intermediate/combination
Snakes Most only have right lung Boids may have two
Expandable
Gas Exchange Counter current mechanism
Simple diffusion of O2 and CO2
Breathing stimulus O2
Indications for Anesthesia Radiographs Surgery Biopsy Physical exam
Anesthetic Agents Injectable
Used less frequently in birds
Inhalants Used routinely for induction in birds Used for maintenance in other species
Pain Management Opioids
Butorphanol NSAIDS
Meloxicam (Metacam), Carpofen (Rimadyl) Local/topical
lidocaine
Equipment Anesthetic machine Anesthetic masks ET tubes
2.0 – 6.0 i.d. Non-cuffed and cuffed 14g – 16g IV catheters Paper clip/hemostats as speculum
Equipment Heat source
Heating pads Heat lamps Forced-air warmers Warm fluid bags Rice/bean bags
Equipment IV catheters 26g – 22g Emergency drugs IV/SQ fluids Monitoring
Doppler Temperature probe ECG Etc.
Incubators
IV Access Birds
Jugular vein Ulnar vein Medial tarsometatarsal vein
Reptiles Jugular vein Ventral coccygeal vein Ventral abdominal vein Sub-carapacial
IO Access Birds
Use non-pneumatic bones only!! Ulna Tibiotarsus
Reptiles Femur Tibia Carapace/plastron
IO access can be used the same as IV but with slower volume of infusion
Pre-medication - birds Opioids
Respiratory depression?? Give 30min to 1 hr before anesthesia
NSAIDS Diazepam
Pre-medication/induction -reptiles Opioids NSAIDS Ketamine Medetomidine Telazol Propofol
Induction - birds Isoflurane/sevoflurane
Mask down Start at 5% with 1L/min O2
Asses depth Flaccid wings and legs Eyes closed HR/RR Righting reflex
Maintenance Isoflurane
0.5% - 2% 500ml – 1L/min O2
IPPV DO NOT EXCEED 15 – 20mmHg POP-OFF valve MUST REMAIN OPEN after
breathing 6 – 12 breaths/min
Determining plane of anesthesia Reflexes
Righting reflex Corneal reflex Tongue withdrawal Toe pinch
Monitoring Stethoscope Reflexes Doppler Temperature probe ECG Pulse oximeter Capnograph
Monitoring Birds Heart Rate
> 100 bpm is normal < 100 bpm is of concern
Respiratory Rate 6 – 12 bpm during anesthesia IPPV if shallow or inconsistent
Temperature Birds: 105oF is normal
Monitoring Reptiles (NEW SLIDE) Heart Rate
Varies with species, temperature 30-60 bpm is normal <30 bpm is of concern
Respiratory Rate 4 – 6 bpm during anesthesia IPPV in most instances
Temperature Reptiles: aim for 90 - 95oF during anesthesia
Hypothermia Heat loss
Convection Air exchange at body surface
Radiation Heat loss to surfaces and environment
Conduction Heat loss from contact (i.e. cold table)
Evaporation Heat loss from lungs, skin, exposed tissues
Preventing Hypothermia Forced-air warmers
Can reduce convection, conduction, and radiation losses depending on the blanket type
Heating pads Reduce conduction losses
Heat lamps Reduce radiation losses
Water bath Reduce conduction, radiation losses
Bean/rice stockings Reduce radiation losses
Preventing HypothermiaConvection Conduction Evaporation Radiation
Forced-air warmer
X X X
Heating pads
X
Heat lamp X
Rice/bean stockings
X
Water baths X X
Recovery Wean off gas before the end of procedure Maintain O2 at low flow rate KEEP WARM!!!!!!!!!!!!!!!! Breathing stimulus
Birds: CO2 and O2
Reptiles: O2
If you run into problems, turn off the inhalant anesthetic and proceed to treat the patient
What can go wrong? Hypothermia Respiratory arrest Cardiac arrest death
How to fix/prevent it? Have heat source IPPV, doxapram Atropine, epi., CPR BE PREPARED!!!!
Why do things go wrong? LACK of PREPARATION!!!!! Lack of monitoring Patient kept too deep IPPV not provided on time Underlying disease Unknown physiological reasons
Challenging species Waterfowl
Prone to bradychardia Budgies and Cockatiels
Hypothermia Critical recovery period
Eagles and large birds Excitatory phase during induction Bradychardia May require higher % for maintenance
Challenging Species Reptiles
Usually require IPPV Unpredictable anesthesia Difficult to maintain plane of anesthesia
Conclusion Understand anatomy and physiology in
order to design anesthetic plan and emergency responses
Perform active, aggressive monitoring Proper thermoregulation is essential Be prepared!!!