Equine Anesthesia Flashcards
Horses are _ nasal breathers
obligate
What can produce atelectasis in equine
large, heavy GI tract pressing on lungs
How long should food and water be withheld prior to anesthesia
food 8-12hrs ; water 0-2hrs
NO _ is to fed 24 hours before anesthesia
grain
No _ is to be fed 12hrs before anesthesia
hay
Foals scheduled for general anesthesia are usually allowed to nurse up to _hr before scheduled induction time
1
Horses >_kg will be placed on LA machine
150
_ drugs reduce GI motility which may result in colic
Anticholinergic
Premedication or sedation drugs given IM or IV
Tranquilizers, alpha2-agonists, and opioids
Preanesthetic procedure to prep horse for sx
-Place IVC in jugular vein
-Wash mouth to remove feed
-Feet cleaned and shoes removed or wrapped
-Place P in induction area or adjacent to tilt table
What type of fluids are preferred
a polyionic solution with an alkalinizing effect
Lactated Ringer’s or Normosol-R are most commonly used and are administer rapidly at _-_ml/kg/hr during the early phases of anesthesia since horses are commonly hypotensive then
10-25ml/kg/hr
After hypotension is corrected, fluid admin may be slowed to
5-6ml/kg/hr
What does horse look like with standing chemical restraint
-drooping lower lip
-reluctance to move
-wide based stance
-lack of interest in surrounding activity
Goal of anesthetic induction
render the horse unconscious as quickly as possible so that the transition from standing (sedated) to lateral recumbency (unconscious) occurs with minimal risk of injury
How are induction drugs administered rather than “to effect”
rapid bolus injection (except guaifenesin)
What is the most common anesthetic drug combination for equine induction
xylazine and ketamine (+/- diazepam)
Ketamine admin alone without sedative premed causes
excitement
ketamine is injected _-_min after apparent xylazine induced sedation
3-5
Why is ketamine not used IM in the conscious horse
because the horse may be injured during the period of incoordination occurring while the drug is taking effect
Xylazine-ketamine anesthesia is accompanied by _ _ _ for the first 5 minutes, and usually nystagmus, a strong palpebral reflex, and pupillary dilation
strong muscle tone
Guaifenesin is admin at _-_mg/kg IV to effect to produce sedation/muscle relaxation
50-100
What position is the horse in for anesthesia
on table and pad superficial nerves and muscle groups, forelimb closest to table is pulled forward; separate hindlimb with padding
How is the ET tube placed in a horse
from nostril into ventral nasal meatus and emerges in nasopharynx
Foals should not be intubated with ET tubes smaller than _mm in diameter
10
Adult ET tube sizes
22mm, 26mm, 30mm
Orotracheal intubation is performed _
blindly
Nasotracheal intubation is done for surgeries of the
head and neck
Where is a nasotracheal tube placed
into the ventral nasal meatus and through the trachea
Complications of intubation is similar to those of small animals but an additional concern would be
epistaxis from nasal intubation
Changes in inhalant anesthetic and O2 flow rate occur _
slowly
Horses are more likely to develop ,,and _ with in inhalant agent
-Hypoventilation (seen w/ dorsal recumbency)
-Hypotension (contributes to myopathy)
-Hypoxemia (more common in obese, pregnant, have twisted intestines, and are in dorsal recumb.)
Hypotension in a horse is an arterial blood pressure less than
<70 mmHg
Hypoxemia is a PaO2 less than
<80mmHg
Horses that will be under general anesthesia for longer periods of time are often placed on a
mechanical ventilator
The ventilator replaces the _ _ and scavenger is hooked to the ventilator
reservoir bag
Induction O2 flow rate
8-10L/min
Maintenance O2 flow rate
3-5L/min
Only _ systems are used in LA
rebreathing
Problems occur more frequently and in greater magnitude than during canine anesthesia, more pronounced:
hypotension, hypoventilation, reduction of cardiac output
Monitor of the cardiovascular system include
-Digital pulse palpation
-CRT, MM
-ECG
-Arterial blood pressure (strongly recommended when using inhalant)
How should hypotension be treated
fluids, inotropes, dobutamine used via syringe pump
Monitoring the respiratory system includes
-Observation of rate and rhythm
-Pulse ox
-Capnometry
-Artial blood gas analysis q30-60min
How is hypoventilation treated
either with assisted or controlled ventilation
Normal HR under anesthesia
28-40bpm
Normal heart rhythm during anesthesia
NSR, SA, or 1st or 2nd degree AV block
Normal RR under anesthesia
6-12 brpm
Normal body temp under anesthesia
97-100F
Using TIVA for procedures lasting <1hr produces
-higher blood pressure, less respiratory depression, and more active palpebral reflexes
-good quality recovery
_ _ infused at a very slow rate and inhalant anesthesia reduces amount of inhalant needed, provides muscle relaxation, provides analgesia
triple drip
What drugs are included in the triple drip
guaifenesin, ketamine, and xylazine
What are the benefits of using lidocaine or detomidine infusions and inhalant anesthesia
decrease inhalant agent requirement and provides analgesia
Why should eyes be protected during induction
horses are prone to corneal scrapes
Padding and positioning on sx table prevent
neuropathies and myopathies
What can indicate horse will attempt to get up too soon
nystagmus (rapid) with paddling of limbs
When should horse be extubated
chewing, swallowing, purposeful ear, or limb or tail movement
What may be used for controlled recovery
head and tail ropes
When can horse be returned to stall
when able to walk steadily
Signs of neuropathy
-facial nerve paralysis (drooping eyelid and lip on affected side
-radial nerve paralysis (inability to fully extend affected forelimb)
Signs of myopathy
hard, swollen muscles, stiff and painful gait
Signs of colic
rolling, kicking at the abdomen
