20 Equine Anesthesia I - START FINAL CONTENT

temperament

large body mass

thoracoabdominal anatomy

response to medication

flight animal (escape mentality can lead to serious injury)

what is a unique set of problems found with equine anesthesia? (5)

false, very HIGH mortality rate compared with other species. Equine anesthesia related mortality rate is 0.1-1% while humans is 0.1%, dogs is 0.17%, and cats is 0.24%

T/F horses have a very low mortality rate (0.01%) associated with anesthesia compared with other species

emergency and out of hours procedures

very old or very young

duration of anesthesia (3 hours)

type of surgery (fracture repair)

what are some circumstances that are associated with even higher rates of anesthesia related mortality rates in horses? (4)

3 hours

fracture repair steps

what duration of equine anesthesia is related to higher mortality rates?

what specific type of surgery is associated with higher anesthesia related mortality rates in horses?

true

T/F the more sick the animal is, the higher the risk of anesthesia related death

True

T/F we would much prefer standing sedation for equine procedures over laying them down

phenothiazines

a2 agonists

opioids

what three groups of agents are primarily used for standing sedation in horses?

acepromazine

what phenothiazine is most commonly used for standing sedation in horses?

Xylazine

romfidine

detomidine

dexmedetomidine

what a2 agonists are most commonly used for standing sedation in horses? (4)

butorphanol

morphine

what opioids are most commonly used for standing sedation in horses? (2)

false, you get some sedation but not typically enough to do procedures

T/F you get fantastic sedation in horses when using acepromazine

a2 agonists

what group of agents are most commonly used for standing sedation and anesthesia in horses because they are fairly reliable?

true

T/F all MOAs, side effects, and effects of the drugs we use for standing sedation in horses are the same as with small animal patients

calm

relaxed

acepromazine produces a _______ and ________ state in horses

15-30 minutes (onset of action)

6-10 hours (duration of action)

what is the onset of action and duration of action of acepromazine in horses?

false, offers minimal muscle relaxation or ataxia

T/F acepromazine offers great muscle relaxation and therefore, ataxia, in horses

hypotension

ischemic priapism

what are two side effects associated with acepromazine in horses?

alpha 1 blockade

what causes hypotension associated with acepromazine?

benztropine mesylate

what is the treatment for ischemic priapism associated with acepromazine in horses?

no

no

does acepromazine offer analgesia?

is there an reversal agent for acepromazine?

true

T/F we tend to avoid using acepromazine in stallions because it may cause their penis to remain dropped for a very long time

sedation

analgesia

muscle

colic

sedation

a2 agonists produces reliable ________, _________, and __________ relaxation and they can provide temporary relief of ________ pain and ________ prior to anesthesia

Dropped head

ataxia

sedation via a2 agonists in horses is characterized by what two things?

can tell horse is at peak sedation when head is hanging 2 feet from the ground (pretty reliable indicator for this class apart from with romfidine)

what is the 2 foot rule in adult horses with regards to a2 agonists?

romfidine

With which a2 agonist do horses tend to keep their head up while maintaining the same amount of sedation and analgesia?

AV block

depressed respiration

decreased cardiac output

increased frequency and volume of urination

nasal and pharyngeal collapse

paradoxical aggression

unexpected kicking

what side effects are associated with a2 agonists in horses? (7)

false, sedation lasts longer than analgesia

T/F analgesia lasts longer than sedation with a2 agonists

Sedation lasts longer than analgesia

why might unexpected kicking be a side effect with a2 agonists in horses?

true

T/F a2 agonists block aquaporins at collecting ducts so they are unable to concentrate urine which can lead to dehydration in sicker horses if given to them a lot (these horses may need to go on fluids)

sedation

analgesia

premed for anesthesia

post anesthesia recovery

what are four clinical uses of a2 agonists in horses?

detomidine (+/- butorphanol)

dexmedetomidine

what two a2 agonists may be used as a CRI in horses?

colic

a2 agonists are good analgesics for what particular condition in horses?

Analgesia

What are opioids used for in horses?

A2 agonists

phenothiazines

opioids are most often used in combination with which two other drug classes?

butorphanol

morphine

methadone

hydromorphone

fentanyl

what opioids might be used in horses? (5)

butorphanol

head bobbing

what opioid is most commonly used with horses? What is a common side effect associated with its use in horses?

morphine

what opioid is clinically useful at lower doses in horses?

may cause nervousness and excitability

GI tract stasis

a2 agonists

what are two potential side effects of opioids in horses?

Due to these side effects, what other drug class is often used with opioids?

IV

IM

xylazine may be given via what two routes in horses?

5 minutes (IV)

15 minutes (IM)

15-30 minutes (duration)

what is the onset of xylazine in horses when given IV? What about when it is given IM?

what is the duration?

2 hours

residual sedation and ataxia caused by xylazine in horses can last up to how long?

true

T/F of the a2 agonists, xylazine has the least specificity for the a2 receptor and highest mortality rate in small animal patients

True

T/F xylazine is starting to be scheduled in some states because it is being mixed with fentanyl on the streets

5-10 minutes (onset)

up to 2 hours (duration)

what is the onset and duration of detomidine in horses?

false, horses seem to plant feet better with detomidine than with xylazine

T/F horses seem to plant their feet better with xylazine than with detomidine

laceration repair

enucleation

flank approach to abdomen

what are three examples of standing surgical procedures in which detomidine may be administered as a CRI for in horses?

true

T/F detomidine may be given epidurally when combined with morphine in horses

detomidine

romfidine has a similar onset and duration in horses as with what other drug?

less ataxia

hold up head

What are two things that make the use of romfidine in horses unique compared to other a2 agonists?

dental procedures

since horses tend to hold their head up more on romfidine, what kind of procedures might it be preferred for?

False, romfidine not detomidine

T/F BI stopped producing detomidine so it can only be compounded, therefore, it is not super commonly used anymore

ketamine

diazepam/midazolam

guaifenesin

what three drugs are the most commonly used drugs for intravenous ("field") anesthesia?

sedatives

prior administration of what drugs is recommended for smoother induction and recoveries when using intravenous anesthesia on horses?

ketamine

what is the most commonly used induction agent in horses?

NMDA antagonist

what is the MOA of ketamine?

Benzodiazepine

a2 agonist

what two drug classes may ketamine be combined with for muscle relaxation?

short

5

15 minutes

top up

ketamine offers a (choose one: short/long) duration of surgical anesthesia -> _ to __ _________ and it can be used for "__ __" anesthesia

tiletamine

zolazepam

telazol is a combination of what two drugs?

ketamine/benzodiazepine

inductions with telazol are similar to that of what other drug combination?

2 times

the duration of surgical anesthesia provided by telazol is about _ ______ that of ketamine

true

T/F telazol can be associated with very rough recoveries in horses and in general, is not recommended for use in horses (though, because it comes as a powder to be diluted, it may be a good option for darts or pole syringes because it can be ultra concentrated into very small volumes)

true

T/F propofol is associated with smooth inductions and recoveries and its side effects are similar to thiopental

difficult to inject large volume rapidly enough to prevent excitement stage of anesthesia

foals, minis, donkeys

what is a big down side of using propofol as a sole induction agent in adult horses?

What equids is its sole use more appropriate in?

Ketamine

propofol is useful as a co-induction agent with what other drug?

hypotension

respiratory depression

what are the two big side effects of propofol?

guaiphenesin (GG)

what intravenous agent is a central acting muscle relaxant used in conjunction with other agents most commonly as a 5% solution combined with ketamine and xylazine in what is referred to as a "triple drip"?

hemolysis

higher than 10% solution of guaiphenesin may cause what adverse effect in horses (we typically use a 5-10% solution)?

field anesthesia

________ ____________: anesthesia performed away from a hospital (ambulatory practice) setting using intravenous agents for induction and maintenance

true

T/F field anesthesia is the most common type of anesthesia for horses (used for greater than 90% of anesthesia events in horses including for castrations, lacerations...) and is often used as anesthesia for emergencies

1 hour

field anesthesia total anesthesia time should be kept under _ ______

single injection

top up (multiple boluses)

constant rate infusion (triple drip)

what are three anesthetic techniques used for field anesthesia?

short procedure (15-30 minutes)

what are indications for using single injection as field anesthesia technique?

premed with xylazine (+/- butorphanol)

induction with ketamine (plus a muscle relaxant)

what is the technique (drugs used as premed and induction agent) for single injection field anesthesia in horses?

ketamine

single injection field anesthesia in horses may be topped up with small additional doses of ________ to prolong anesthesia

Ketamine

xylazine (or other a2 agonist)

5% guaifenesin

what are the three components of a triple drip?

1-3 ml/kg/hr (1-2 drops/second for 450 kg adult)

What is the rate that a triple drip should be set in horses?

45 minutes

a triple drip can be used for about __ _______ without the horse getting to toxic levels

can cause tissue necrosis (if gets outside of vessel)

why must guaifenesin be delivered through an IV catheter?

Effect

a triple drip is delivered to _________

respiration

hypoxemia

hypercapnia

apnea

a triple drip can depress muscles of __________

which can result in what adverse effects? (3)

heart rate

ventilatory rate

typically only what two parameters are monitored when a horse is on a triple drip?

false, IV protocols generally have shorter and more coordinated recoveries compared to inhalant anesthesia

T/F Inhalant anesthesia generally has shorter and more coordinated recoveries compared to IV protocols

padded recovery stall or outdoors in an open area to prevent injury

where should recovery from IV anesthesia in horses occur?

true

T/F before administering local anesthesia in horses, you should always aspirate the syringe first to ensure you are not in a blood vessel!

lidocaine

mepivacaine

bupivacaine

what three local anesthetic agents are most commonly used in horses?

moderate

2-4 hours

short

1-2 hours

long

4-8 hours

mepivacaine has a (choose one: short/moderate/long) duration of action - _-_ ______

lidocaine has a (choose one: short/moderate/long) duration of action - _-_ ______

bupivacaine has a (choose one: short/moderate/long) duration of action - _-_ ______

cardiotoxic

Local anesthetics other than lidocaine can be __________ and should NEVER by administered IV

Auriculopalpebral n

supraorbital n

when providing local anesthesia to the equine eye, what two nerves are typically targeted?

auriculopalpebral n (branch of facial n)

orbicularis oculi m

When blocking the equine eyelid MOTOR function, what nerve are we targeting? What muscle?

zygomatic arch

spasm

corneal

the auriculopalpebral nerve is palpable across the _________ ______ in horses and when it is blocked, it relieves eyelid ________/permits ________ examination/surgery

False! Does NOT provide analgesia, only motor block

T/F an auriculopalpebral block offers analgesia of the equine eye to facilitate ophthalmic procedures

supraorbital n

What nerve is a branch of the trigeminal nerve and is blocked just cranial to the dorsal rim of the eye in order to block sensation to the upper eyelid?

True

T/F you should use a small gauge needle to infiltrate 2-5 mL of local anesthesia per site when blocking the equine eye

dental procedures

Anesthesia for the teeth and face in horses is typical done for what type of procedures?

standing under sedation

floating teeth

trimming hooks

removal of wolf teeth

extractions

anesthesia for the teeth and face in horses is typically performed while the horse is ________ ______ _________

what four dental procedures commonly indicate the use of teeth and face anesthesia in horses?

maxillary n

ipsilateral nose, face, upper lip, dental structures rostral to block

The infraorbital nerve is a branch of what nerve?

what parts of the face does an infraorbital nerve block desensitize?

point of emergence from infraorbital foramen under levator nasolabialis muscle

where, anatomically, is the infraorbital nerve blocked in horses?

horses unable to flair nostrils resulting in airway obstruction (especially when you block both sides)

what is a possible complication of infraorbital nerve block in horses?

as it exits maxillary foramen

upper arcade of teeth

where, anatomically, is the maxillary nerve blocked in horses?

what does a maxillary nerve block anesthetize?

true

T/F similar to an infraorbital nerve block, a maxillary nerve blocked may cause the horse to be unable to flair its nostrils