Exotics: Anaesthesia of Exotics Flashcards
What are the defenitions of ASA 1-5?
ASA 1- normal healthy patient
ASA 2- mild systemic disease
ASA 3- Obvious systemic disease
ASA 4- severe systemic disease, constant treat to life
ASA 5- not expected to survive without the operation
What avian patients are of specific concerns?
No commonly kept
* Ratites
* Cranes
* Flamingos
* Charariforms (waders)
* Penguins
* Marine/diving birds
What are general considerations for avian anasethesia?
- High incidence of chronic and subclinical disease
- Susceptiple to heat loss and hypothermia
- Most species no domesticated- peri-anaesthetic stress
- Small species- difficult IV access, limited monitoring
- > morbidity/mortality
- What species do not have nostrils?
- What is the route of air through nostrils?
- Cormorants, pelicans, gannets
- Nasal cavities to infraorbital sinuzes to cervico-cephalic air sacs- reduces in diameter
Diameter > trachea
Glottis not visible in flamingos
- What species do not have nostrils?
- What is the route of air through nostrils?
- Cormorants, pelicans, gannets
- Nasal cavities to infraorbital sinuzes to cervico-cephalic air sacs- reduces in diameter
Diameter > trachea
Glottis not visible in flamingos
How are birds ETT related to anatomy?
- Complete/partiall overlapping rings- uncuffed ETT
- Proximal narrowing of lumen- ETT advancment
- Long complez shapes (cranes, swans) > dead space
- Bifurcated in some species
What is the syrinx?
What can cause a complication with ETT in pigeons and ducks?
Syrinx- bifurfaction of major bronchi responsible for vocalisation during insp/expiration
Tracheal mucus can cause partial/complete ETT obstruction increased in pigeons and ducks
- Which position reduces ventilation of birds and why?
- What can compress air sacs?
- reduced ventilation on dorsal recumbancy (pecoral muscles weight)
- Compressed by effusions, enlarged organs or fat deposits
Birds have higher O2 demands- counter-current
What are the different air sacs in birds?
Paired
* Cervical
* Cranial thoracic
* Caudal thoracic
* Abdominal
Unpaired: clavicular
Why do birds have a higher tolerance to haemorrhage and anaemia?
Why does renal excretion of drugs need to be considered before use?
RBCs have a shorter half life
Renal portal system
How should bird be prepared before anaesthesia?
- Weight taken
- Complete clinical exam
- Fasting- not advised <500g, 2-4 hours for larger, comfirm crop empty
- If possible correct any abnormality prior to anaesthesia: glucose
- Eye lubricant
- Mentation- hypoglycaemia, bradycardia, dyspnoea, neuro
- MMs- pigmented
- African greys- hypocalcaemia
- What are indications for sedation of birds?
- What are the important effects?
- What is often used?
- Clinical exam, short procedures, pre-med for anaesthesia
- Reduces stress of handling, anaesthetic sparing, amnesic effect
- Midazolam 0.5-2mg/kg + butorpahnol 0.5mg/kg IM
reverse with flumazenil = volume midazolam
Other then midazolam what can also be used for sedation?
What is the dose in budgies, rattites, cranes?
Alfaxalone- period of exitability, apnea on induction, variable recovery
Budgies- 10-15mg/kg IM
Birds of prey 10mg/kg IM
Cranes- 7mg/kg IV
When are the following types of drugs used in birds?
Parasympatholytics
Alpha-agonists
Propofol
Parasympatholytics- Bradycardia/CPR situations
Alpha-agonists- birds resistant to effecs, combine with ketamine
Propofol- induction for larger species?
causes resp depression, apnoea, hypotension
What can be used for field conditions for injectable anaesthesia?
Midazolam 1mg/kg + butorphanol 1mg/kg
Ketamine 3-7mg/kg + metomidine 0.07-0.1mg/kg IM reverse with atipamezole
What NSAIDs and Opioids are used in birds?
What are toxic?
NSAIDs:
Meloxicam- varying doses
Carprofen
Opioids:
Butorphanol
Buprenorphine
Fentanyl- bradycardia, hypotension, sedation
Tramadol- post-op
TOXIC:
Flunixin meglumine
Ketoprofen
Diclofenac
What can be used for local anaesthesia in birds?
Lidocaine and Bupivicaine combination
Line, splash, brachial plexus block
What veins are used for venous access in birds?
Medial metatarsal vein: poultry, waterfowl
Ulnar (brachial vein): IV needs to be butterflied and sutured in
Intra-osseous catheters: smaller species, proximal tibiotarsus, distal ulna
When should a face mask be used?
- Short, non-invasive procedures
- Induction for ETT placement
When would an abdominal air sac tube be placed?
- Oral/tracheal surgery
- Upper airway obstruction
- Induction with facemask
- Cuffed ETS in emergency
What are the choices of gas anaesthesia for birds and considerations of both?
Isoflurane
* Induces arrythmias, tachycardia and hypertension in some birds of prey
* Decreases ionized calcium
* Induction 3-4%, maintenance 1-2%
Sevoflurane
* Lower blood solubility
* Faster induction/recovery
Non-rebreathing systems- T-piece
What is monitored directly during GA in birds?
Direct observation
* Palpebral/corneal reflex
* Wing tone
* Feather plucking reflex
* Deep pain/toe pinch reflex
* Sudden feather erection > cardiac arrest
* Clocacal reflex
HR values > or < baseline are abnormal, shifts/trends, oesophageal stethoscope in larger patients
RR chest movements- deep, increased etc
How is the patient monitored with equipment during GA?
- Doppler probe on ulnar artery
Conscious psittacines 90-180mmHg, GA 90-150mmHg - Pulse oximeter- larger species
- Electrocardiogram- attaching leds and keeping a good sign is difficult
- Temperature- cloacal probes
- Capnography- accuracy variable
What problems can arrise from GA of birds?
- Hypothermia
- Blood loss/hypovolaemia
- Brady cardia
- Hypotension
- CR arrest- window for resuscitation <30s
- Post-ETT tracheal stenosis- 1-3 weeks post anaesthesia, too wide ETT
How should GA complications in birds be approached?
- Confirm ETT is patent
- Stop anaesthetic gas
- Start IPPV
- Hypertonic saline 3ml/kg/IV/IO until BP >90mmHg
- Crystalloids and colloids
- Consider dextrose
- Atropine
- Start chest compressions
- Adrenaline
Describe recovery from GA for birds?
- Stop anaesthetic gas delivery while providing O2
- Remove IV/IO catheters
- Check glottis for mucus build up after removing ETT
- Incubator- careful with handling and orthostatic hypertension, inc risk of hypotension and hypoglycaemia, careful with hyperthermia
What is important to note about for anaesthesia of reptiles?
- Poikilothermic- cannot regulate body temp
- POTZ for each species
- Typically long recoveries
What is notable about reptiles CV system?
- Most species have 3 chambered heart: 2 atria 1 ventricle (muscle ridges prevent mixing)
- Renal portal system: blood from 1/2 caudal body can reach kidneys
- Hepatic portal system- blood from 1/2 caudal body passes the liver before general circulation, drugs metabolised by liver admin on forelimbs
What happens to reptiles with increased/decreased environmental temp?
Increase
* cutaneous vasodilation
* BP reduces and HR increases
* L to R heart shunt
* Warmed blood returns and increases body temp
Reduction
* Cutaneous vasoconstriction
* Blood pooled in muscles keeps body heat
* HR reduces
How is apnea and hypoxia different in reptiles?
Very tolerant to myocardial hypoxia
Diving reflex in acquatic reptiles
* Bradycardia and direct blood to vital organs
* R to L shunt and bypassing pulmonary circuit
* Reserved with first post-dive breath
What respiratory physiology is important for anaesthesia of reptiles?
Significant variation
* Anaerobic metabolism
* Some resp exchanges in skin and mucosa of species
* Hypoxia increases RR
* Hypercapnia increases tidal volume
* High O2 environment depresses RR- recovery and CPR
* Temperature- increases demand of O2, increases tidal volume
Briefly describe the unique chelonians respiratory anatomy?
- Short trachea with complete rings- short uncuffed ETTs
- Dorsal sac-like lungs: insp/exp active process
- No intercostal muscles
- Ribs fused with shell
- 2 paired antagonistic abdominal muscles
- Horizontal septum
- Gular movements- not RR
