Avian Anesthesia Flashcards
What is the larynx of birds like?
4 cartilages (procricoid, cricoid, 2 arytenoids) No epiglottis or thyroid or vocal cords
What is the trachea of a bird like compared to mammals?
3x longer and 1.3x larger, so they have increased dead space and decreased resistance
What is the minute volume (Ve) of birds compared to mammals?
1.5 to 2 times greater
True or false: birds have complete tracheal rings
True
What makes sound in a bird?
Syrinx
What is unique about penguins?
There is a septum that starts at the division of main bronchi and extend rostrally and may appear to have a double trachea and need 2 ET tubes
Since birds don’t have a diaphragm, what is ventilation driven by?
Respiratory muscles both in inspiration and expiration
How many air sacs do birds have?
Up to 9 (2 cervical, 1 clavicular, 2 cranial thoracic, 2 caudal thoracic, 2 abdominal)
What are the air sacs covered in?
Simple squamous epithelium and connective tissue
True or false: air sacs participate in gas exchange.
False, they are just a sort of air reservoir
Describe primary bronchus
1/lung
Left and right bifurcate at the syrinx
Continues into abdominal air sacs
Describe secondary bronchi
4 groups arise from primary bronchus that are interconnected (medioventral, mediodorsal, lateroventral, laterodorsal)
Muscular and elastic fibers
Opening into air sacs
Describe tertiary bronchi
Gas exchange component
Paleopulmonic (all birds, unidirectional)
Neoplumonic (bidirectional): penguins, poultry, singing birds
What is the atria like in birds?
Numerous pocket-like polygonal cavities
Open into the lumen of the parabronchi
Contain openings that lead to air capillaries
What does the small diameter of air capillaries result in?
Greater pressure gradient for oxygen diffusion
Why is gas exchange more efficient in birds?
It happens along the entire length of parabronchi giving an overall bigger surface exchange area
Thinner distance between parabrinchus and capillary
Longer blood supplies (retinacula)
How is ventilation controlled?
Both central and peripheral chemoreceptors
Intrapulmonary chemoreceptors –> CO2 sensitive –> vagal negative feedback (decreased CO2 stimulates receptros) –> inhibits respiration
How many chambers are in the heart of a bird?
4
Why do birds have a larger CO?
Larger SV and lower HR
Because birds have a higher SAP (105-220 mmHg), what can occur?
Aneurism and arterial rupture
What is the conduction of the heart of birds?
Type II hearts
What is the QRS like in birds?
Negative, no ST segment
What is the renal portal system?
Valve located at the junction between efferent renal vein and external iliac vein
What happens if the renal portal valve is open (epinephrine)?
Blood bypasses kidneys
What happens if the renal portal valve is closed (Ach)?
Blodd passes through the kidneys
What happens during diving?
Reduction in O2 consumption
Reduction N2 absorption
What happens with a reduction in O2 consumption during diving?
20% O2 from respiratory volume, 40% from Hb and 40% from muscles
Bradycardia and vasodilation
Shifting blood to brain, lungs, and heart
What happens with a reduction in N2 absorption?
Reduction in respiratory volume
Bradycardia –> reduction in CO –> reduciton in N2 uptake
Tachycardia and vasodilation in emersion –> dissipation cumulated N2
What should glucose be maintained at?
> 200 mg/dl
How long should a bird be fasted?
2-4 hours
What are the IM injection sites?
Pectoral or thigh muscles
What are the IV injection sites?
Medial ulnar vein
Dorsal metatarsal vein
Jugular (R>L)
What are the SQ injection sites?
Between wings, inguinal fold of skin
What are the IO injection sites?
Proximal tibio-tarsus or distal ulnar
Avoid pneumatic bones
How much crystalloid should be given?
4 times the loss –> interstitial space in birds is 4x the blood volume
What is the dose of hypertonic saline?
4 ml/kg
What is the dose of colloids?
Hetastarch 5-10 ml/kg or 20 ml/kg/die
At what ratio to the loss should blood be give?
1:1
What do antimuscarinics cause?
Increased thickness of respiratory secretion
What do benzodiazepines do?
Sedation, hypnosis, anxiolysis, anterograde amnesia, centrally mediated muscle relaxation and anti-convulsion
What can benzos be reversed with?
Flumazenil
What does xyalzine (alpha2-agonist) cause?
Profound sedation with bradyarrhythmias, arrhythmias, excitement, and seizures
What is the 1st choice of opioids in chickens and psittacine?
Butorphanol
What has been shown to work well in raptors?
Mu-agonists
What is the problem with diclofenac and ketoprofen?
Causes ARF in brids
At what dose does carprofen work in chicken?
High doses (30 mg/kg)
What does carprofen cause in pigeons?
Acute liver and muscle necrosis
What is the 1st choice of NSAIDs in birds?
Meloxicam
What is the problem with local anesthetics?
Very sensitive to local anesthetics and can suddenly die if accidentally injected IV
What is the problem with ketamine in snowy owls?
Can cause arrhythmias and violent recoveries
What is ketamine usually associated with?
α2 or benzos
What does propofol cause?
Apnea, hypoxia, and very unreliable anesthesia
Why do you not use propofol in chickens and pigeons?
Toxic dose is close to induction dose
What is the gold standard for anesthesia?
Inhalant anesthesia with mask induction or in an anesthetic chamber
What is MAC in birds?
Minimal anesthetic concentration
What is the apneic index in birds?
1.65%
How do you know if a bird is unconscious?
Loss of rightening reflex
How do you know if a bird is in the surgical plane of anesthesia?
Loss of muscle tone in wings and legs, toe pinch response
Corneal reflex, but not palpebral
How can you measure doppler?
Superficial ulnar artery
Deep brachial artery
Dorsal tibial artery
Palatine artery
What is a normal temp?
39-43C (102.2-109.4)
Why do birds tend to lose more heat than bigger animals?
They have a higher surface-area-to-mass ratio
Which is more common, respiratory arrest or cardiac arrest?
Respiratory
