Chapter 44
Anesthetic Management of Birds
A fine feathered friend!
Katrina Lafferty
University of Wisconsin-Madison, University of Wisconsin Veterinary Care, USA
- Q. What are common reasons that birds require anesthesia?
- A. There are numerous cases where an avian patient may require anesthesia. Leg, wing, and beak fractures are common presentations. Birds often suffer reproductive issues requiring surgical intervention. Examples include repairing a prolapsed cloaca or removing a retained egg. Endoscopically-guided crop, liver, and gastrointestinal biopsies are routinely required for a diagnosis and will require general anesthesia. In some cases it may be safer, easier, and less stressful to anesthetize a bird, rather than physically restrain it, for minor procedures such as beak trims, implant placements, radiographs, or larger volume venipuncture [1].
- Q. Are there any concerns when restraining avian patients?
- A. Birds have a unique respiratory system that is easily compromised by overzealous restraint. Birds have no diaphragm and utilize thoracic musculature for both inhalation and exhalation [2]. Restriction of the thoracic cavity will inhibit adequate breathing/tidal volume. Birds have complete tracheal rings, but these can be collapsed during aggressive manual restraint [1].
- Q. What should be evaluated in a pre-anesthetic exam?
- A. The pre-anesthesia examination requirements in birds are essentially the same as for canines and felines. Basic information should include weight, body condition, hydration status, and auscultation of the heart, dorsal lungs, and ventral air sacs [1,3]. If possible, blood should be collected for laboratory work; packed cell volume (range 35–55%), total protein (range 3.5–5.5 g/dl), and blood glucose (∼200 mg/dl) are the bare minimum needed before anesthesia. The benefits of pre-anesthetic blood work should be weighed against the risks of restraint [1]. Venipuncture can also be done after sedation.
- Q. For how long should avian patients be fasted before anesthesia?
- A. Having an empty crop and stomach reduces the potential for regurgitation and aspiration of gastric contents. For patients in dorsal recumbency, fasting can decrease pressure on the lungs from the weight of the stomach and intestines. The suggested duration of fasting is generally 1 h per 100 g of body weight. For example, a parrot weighing 600 g should be fasted for about 6 h. For birds less than 100 g, fasting is not recommended. In critical cases fasting may not be an option before anesthesia. In these situations intubation is a must. Keeping the head elevated during anesthesia and recovery may reduce the risk of regurgitation and aspiration [4].
- Q. Should avian patients receive premedication before anesthesia?
- A. All avian patients (regardless of species) should receive premedication before general anesthesia. Premedication reduces fear, stress, and anxiety in patients. Handling of unsedated birds can cause a physiologic stress response that may result in decompensation, collapse, or death. Sedation of avian patients reduces stress and can facilitate minor procedures such as examination, venipuncture, and radiographs [5]. Premedication makes for a smoother induction to general anesthesia and reduces the amount of inhalant anesthetics required for induction and maintenance [3].
- Q. What sedatives are safe to use in birds as premedications?
- A. Benzodiazepines are considered safest for avian sedation. They cause little respiratory or cardiovascular depression and are reversible. Unlike mammalian species, birds become quite sedate after benzodiazepines are administered. Midazolam is the preferred choice; it is water-soluble and safely administered by various routes. Higher doses result in more profound sedation; this may or may not be desired depending on procedure and patient temperament. Midazolam is reversed with flumazenil [1,6]. See Table 44.1 for drugs and doses.
Table 44.1 Sedation and analgesia drug doses [1,6–8].
Drug
Dose
Comments
Midazolam
0.2–2.0 mg/kg (IM,IV,IN)
Generally lower doses needed IV
High doses result in more profound sedation
Flumazenil
0.02–0.1 mg/kg (IM,IV,IN)
Reverses benzodiazepines
Butorphanol
0.5–4 mg/kg (IM,IV)
Butorphanol CRI
0.075 mcg/kg/min (IV)
May require loading dose
Naloxone
0.01–0.04 mg/kg (IM,IV)
Reverses opioids(reverses ALL analgesia)
IM=intramuscular; IV=intravenous; IN=intranasal
- Q. What opioids are safe to use in birds?
- A. For non-painful procedures (radiographs, venipuncture, etc.) it is acceptable to use sedatives alone. For any situation where pain can be expected, however, a balanced anesthetic approach involving sedatives and analgesics should be provided. Much conflicting information exists on which analgesics work best for birds. Current research suggests that, unlike mammals, most avian species receive adequate levels of analgesia from butorphanol [1,6–8]. In psittacines, butorphanol can be given as a constant rate infusion to maintain analgesia [6]. See Table 44.1
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- Q. Are there any concerns when restraining avian patients?
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