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What can lead to nasal congestion in an equine patients?
venous drainage of the horse's head occurs passively (with gravity); therefore, if they are positioned with their head below their withers, they can develop nasal congestion
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What makes anesthesia of horses challenging? (5)
- "flighty" nature of horses
- large size
- anatomy- GI (prone to colic w/ anesthesia), respiratory (obligate nasal breathers, venous drainage of the head is passive w/ gravity)
- depth of anesthesia may change unpredictably
- rough recoveries
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Why is nasal congestion dangerous for equine patients, and what can you do if it develops?
- it will lead to nasal obstruction, and horses are obligate nasal breathers
- place a nasopharyngeal tube during recovery to keep a patent airway
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What is an additional concern for horses in dorsal and lateral recumbency?
large, heavy GI tract will place pressure on the lungs, causing atelectasis
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How does myopathy occur during anesthesia, and how is it prevented?
- muscle blood flow must be maintained during anesthesia--> if not, leads to muscle hardness, pain, weakness, and "tying up"
- prevent with adequate padding, pulling "down leg" forward
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How is sedation achieved in horses?
alpha-2 agonists!!!!! (xylazine, detomidine, romifidine)
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How do you know when a horse is adequately sedated to move forward with anesthesia?
- reluctant to move
- not interested in surroundings
- head down, lip drooping, ears in neutral position
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NEVER.....
induce anesthesia in a horse that is not adequately sedated
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What is the most common way to induce an equine patient?
ketamine + a benzodiazepine for muscle relaxation as an IV bolus
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Why do we induce horses with a bolus, as opposed to giving induction drugs to effect as we do in other species?
we want a horse to go down quickly so they don’t have time to panic and run away/ freak out
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What is the key to intubating a horse?
- extend the head and neck
- [the easiest place for the tube to go in a horse is the trachea, so if you hit resistance, back up, adjust, and try again]
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How do you know you have successfully placed the ET tube in a horse?
advancement of the tube without resistance indicates successful placement (it's very unlikely to go in the esophagus)
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Use inhalant anesthesia for... (3)
Problems with this include... (3)
- procedures > 1hr, complex procedures, and procedures on compromised patients.
- hypoxemia, hypoventilation, hypotension
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How is direct monitoring of BP achieved in horses?
arterial lines: facial artery, transverse facial artery, dorsal metatarsal artery
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Hypotension during general anesthesia is _________ and contributes to __________; therefore, treat with... (4)
mean BP <70mmHg; myopathy (by decreased blood flow to the muscles); increasing IV fluid rate, decreasing anesthetic depth, surgical stimulation--> then use dobutamine!
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If a horse gets too light during surgery, you should...
give an IV induction drug  of the induction dose
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Describe maintenance of anesthesia with TIVA.
- induction normally with a bolus of IV induction drug (usually ketamine + benzo)
- administer additional doses of alpha-2 agonist and ketamine, usually 1/4-1/5 of the sedation/ induction dose OR use triple drip method
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Why is positioning important for equine anesthesia patients?
- prevent myopathy
- prevent neuropathy (facial nerve paralysis)
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How do you position the limbs of a horse in lateral recumbency?
pull "down" limb forward and place a pad between the legs
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Field anesthesia can be prolonged for up to _________, using the _____(2)____ methods, which is...
1 hour; TIVA or triple drip; [TIVA] total intravenous anesthesia or [triple drip] guaifenesin, ketamine, and xylazine in a bag, drip to effect
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1/3 of all equine anesthetic-related deaths occur during __________ because... (2)
recovery; horses have a psychological desire to stand (often before they're ready), obligate nasal breathers
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How can we make recovery safer for our equine patients? (4)
- sedated recovery w/ alpha-2 or ace (prevent from standing too early)
- physical restraint (kneel on neck)
- assisted with ropes
- nasopharyngeal tubes (obligate nasal breathers)
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You are recovering an equine patient from general anesthesia, and the horse develops nystagmus and paddling of the limbs; you immediately...
sedate the horse with IV xylazine and/or acepromazine because these are signs that the horse will try to get up too soon and have a rough recovery.
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