Avian Anesthesia Flashcards
What is the only compliant structure of a bird’s respiratory system
Air sac (typically 9 - 8 paired and one single)
(Lungs have minimal change with respiration)
Compared to mammals what does the bird larynx lack
They lack an epiglottis
What is the sound producing organ in birds
Syrinx
Where does gas exchange occur in birds
-Parabronchial lungs (tertiary bronchi) and surrounding tissue (more efficient gas exchange than mammals)
*paleopulmonic - main gas exchanging bronchi - unidirectional gas flow seen in all birds
*neopulmonic - bidirectional gas flow seen in some species
-Have air capillaries in the blood vessels instead of alveolar structure
Compared to mammals of similar size, what differs about bird’s dead space, tidal volume, resp rate, and minute volume
- tracheal dead space- 4.5x LARGER
- tidal volume- 5x LARGER
- RR - about 1/3 LOWER
- Tracheal minute volume - 1.5-2x HIGHER
Why is a bird’s minute volume larger than mammals of similar size.
Birds have higher metabolic demand
How many respiratory cycles are needed for air to pass through the lungs-air sac system and can you briefly describe the process of respiration
-2 respiratory cycles
*first inhalation air goes through trachea to caudal air sac. First exhale air goes from caudal air sacs into lungs. Second inhalation air goes from lungs to cranial air sacs. Second exhale air goes from cranial air sac out through the trachea.
(Inhalations expansion of air sacs, negative pressure air in)(exhalation contraction of air sacs, positive pressure pushes air out)
Compared to mammals of similar size how does bird’s heart size, cardiac output, stroke volume, arterial blood pressure, and ECG differences
-Bigger hearts
-higher CO and SV
-higher ABP (species dependent)
-ECG: wide QRS complexes, rates exceeding 200-300 beats/min-> appears similar to ventricular tachycardia in other species
What kind of renal system do birds have and what is the clinical significance of this
-They have a renal portal system meaning that they have dual blood supply (renal artery and portal system)
-blood from hind legs and tail will pass through the kidney before returning to the heart so you should avoid injection in those sites (rapid excretion)
What are sick anorexic birds susceptible to and what should you do for the bird and what do you do if they become dyspnic
-Since birds have high metabolic rate and high energy demand, when they are anorexic (low energy intake) they will become HYPOTHERMIC.
-To reduce energy demand in sick birds place them in an INCUBATOR AT 26-29C (79-84F) with a 70% humidity
-when dyspnea - inspired oxygen concentration to 40-50%
During an avian PE what would you do inside the cage before handling and what do you outside of the cage
Inside: level of consciousness, awareness, body posture, resp rate
Outside: oral cavity, choana, cardiopulmonary auscultation, feather condition, hydration status
What are the injection sites in avian species (IM, IV, IO, SQ)
-IM - pectoral muscles
-IV - jugular vein, superficial plantar metatarsal vein
-IO - proximal tibiotarsus, distal ulna
-SQ - propatagial fold, axilla, precrural fold
What bone(s) in the bird do you want to avoid jn IO catheter placements and why
-Don’t use femur or humerus bones
-they are pneumatic bones so are connected to the air sacs
What are the pre-op fasting times for small birds/ larger birds/ birds of prey
Due to high metabolic rates fasting periods should be minimal
Small birds - no fasting
Larger birds - ~4hours to allow crop to empty
Birds of prey - ~12hours
What the risk of the crop not being empty in birds under anesthesia and what can you do to minimize the risk
- risk of regurgitation and aspiration
-possible fasting and ensuring the head is raised above the crop should prevent regurgitation
What are good premedication that cause sedative effects in avian species
*Midazolam (IM or IN)
-midazolam + butorphanol (IM)
-midazolam + morphine (IM)
What premedications cause various effects in avian species and has a risk of agitated recovery
Ketamine combinations
Alflaxolone
Which is better to induce and maintain anesthesia in avian species inhalant or injectable anesthetics
-inhalant anesthetics is best as you have rapid induction with face mask and fast recovery
-Ketamine injections does not provide adequate surgical anesthesia and recovery is poor
What are two spots in avian species you can intubate and when would you do the one over the other
-Endotracheal intubation (reminder to cut ET tube to minimize dead space and use a low dead space adapter)
-Caudal air sac intubation
*do this when the larynx is obstructed
What is a common complication with ET tube intubation
Mucosal plug obstruction
How do you measure the surgical plane of anesthesia in avian species
-Absent - righting reflex, palpebral reflex, mandibular tone, toe pinching
-present - corneal reflex
*deep plane when they become bradycardic and bradypnea
Do you recommend mechanical ventilation in birds and if so what is the target
Yes ventilate - want a ventilator that can provide wide range of tidal volume
PIP - 4-15cmH2O (depend8g on bird size)
-target PaCO2 between 30-40mmHg
What is the most common complications of anesthesia and why
-hypothermia
-impaired thermoreg due to depressing thermoreg response and cause PERIPHERAL VASODILATION
-They can also lose heat to their surrounding due to high body surface, decreases heat production due to less muscle activity
What is a good non-invasive blood pressure monitor and what are the recommended guidelines
-Doppler
-ideal cuff size 40-50% of limb circumference
