(2) Avian and Exotic Animal Anesthesia

Avian and Exotic Animal Anesthesia

Javier G Nevarez DVMjnevarez@vetmed.lsu.edu

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!!!