Chemical Restraint, Locals, & Epidurals

Question 1

What are the main contributing factors to mortality related to anesthesia/sedation in horses?

Answer 1

(Age (the younger or older, the worse off), duration of the surgery, the drugs used for sedation, and inhalants used)

Question 2

In preparation for sedation in the field of a horse, you should perform a physical exam paying special attention to which systems?

Answer 2

(Respiratory and cardiovascular)

Question 3

What are the three more common arrhythmias found in horses?

Answer 3

(1st degree AV block, 2nd degree AV block, and atrial fibrillation)

Question 4

A murmur is innocent if it is found in a foal of what age?

Answer 4

(Anywhere from 10 days to 2 weeks, anything past that should be evaluated)

Question 5

What are the possible routes of administration available for alpha 2 agonists in horses and which is the fastest to reach the desired effect?

Answer 5

(PO, IM, and IV, IV is the fastest)

Question 6

How long does it take to reach the peak effect for IV versus IM administration of an alpha 2 agonist in a horse?

Answer 6

(IV → 3-5 minutes, IM → 10-15 minutes)

Question 7

Of the alpha 2 agonists available for use in horses, which is more potent?

Answer 7

(Detomidine is more potent than xylazine)

Question 8

Why do alpha 2 agonists increase urination in horses?

Answer 8

(Induces a transient hyperglycemia that causes osmotic diuresis and increased urination, they also inhibit ADH)

Question 9

(T/F) When using an alpha 2 agonist for sedation and/or as a premedication, it should always be reversed.

Answer 9

(F, you’ll have a better recovery if you can avoid reversing)

Question 10

What is the classical stance horses take when they are sedated with alpha 2 agonists?

Answer 10

(The 5 point stance)

Question 11

What is the potential complication associated with giving acepromazine and then maintaining anesthesia with inhalants in horses?

Answer 11

(Hypotension)

Question 12

What is the onset of action and duration of action for acepromazine in horses?

Answer 12

(Onset → 15-30 minutes, duration → 6-10 hours)

Question 13

Is acepromazine or xylazine more likely to induce ataxia in horses?

Answer 13

(Xylazine)

Question 14

Is acepromazine or xylazine going to have some analgesic effect in addition to sedation?

Answer 14

(Xylazine)

Question 15

Why should acepromazine be used with caution in breeding stallions?

Answer 15

(Can cause priapism)

Question 16

Is acepromazine or xylazine going to be more effective as an adjunct to dissociatives?

Answer 16

(Xylazine)

Question 17

Why should opioids mostly be used as an adjunct to tranquilizers and not alone?

Answer 17

(They can cause excitement)

Question 18

What is the duration of action of the ketamine/alpha 2 agonist combo?

Answer 18

(15-20 minutes)

Question 19

How can you increase your chances of a drug protocol working that uses xylazine and ketamine?

Answer 19

(Give the xylazine first and allow the horse to become sedate before giving the ketamine (giving them together is not as desirable and ketamine should not be given to an excited horse), do not disturb the horse until it is recovered, and ketamine should only be given IV)

Question 20

What is the purpose of adding diazepam to your xylazine/ketamine drug protocol?

Answer 20

(Allows for a smoother induction and greater muscle relaxation)

Question 21

Why is there a potential for prolonged and/or rough recoveries when using a xylazine/telazol combo?

Answer 21

(Bc the telazol lasts a lot longer than the xylazine so the horse will have a dissociative on board longer than a tranquilizer and recovering on just a dissociative sucks → avoid by using detomidine instead of xylazine, will also give you a longer duration of anesthesia)

Question 22

(T/F) TKD does not induce a surgical plane of anesthesia and should not be used alone for a surgical procedure.

Answer 22

(T)

Question 23

What type of drug is guaifenesin?

Answer 23

(Muscle relaxer, nothing else)

Question 24

What are the signs associated with a guaifenesin overdose?

Answer 24

(Stiffening and extension of the forelimbs, labored breathing that is similar to a horse reaching light anesthesia, and eventual respiratory and cardiac arrest)

Question 25

Of the benzodiazepenes available for use in horses, which can be given both IV and IM?

Answer 25

(Midazolam, diazepam is IV only)

Question 26

What side effect of propofol limits its usefulness in the field when working with horses?

Answer 26

(Respiratory depression)

Question 27

Recovery of a horse that was administered GKX/triple drip to maintain anesthesia depends on what?

Answer 27

(The total dose administered, the more muscle relaxer you give the more difficulty the horse will have getting up post op)

Question 28

GKX/triple drip can be used to induce (in foals)/maintain anesthesia safely for up to how long?

Answer 28

(One hour, should supplement O2 if sx longer than 30 minutes, can sub midazolam for GG d/t cost)

Question 29

What change do you expect to see in the respiratory signs of a horse that is getting light?

Answer 29

(Respiratory rate becomes more rapid and the breathes become more forceful)

Question 30

What is the duration of lidocaine vs. mepivacaine vs. bupivacaine?

Answer 30

(Lidocaine → 1-2 hours, mepivacaine → 1-2 hours, and bupivacaine → 4-6 hours)

Question 31

Blocking what nerve is the most important block to prevent a horse from clamping its eye shut during an exam or procedure?

Answer 31

(Auriculopalpebral is the most important eye motor block)

Question 32

Why should you choose to use something short acting for your auriculopalpebral block?

Answer 32

(Bc the animal can’t blink which is bad for the eye for longer durations, want something that will wear off sooner than later)

Question 33

Blocking which nerve will block the sensory innervation to most of the upper eyelid in a horse?

Answer 33

(Supraorbital)

Question 34

Pair the following nerve to what they innervate (and what you would block if you were to block those nerves):

Lacrimal
Infratrochlear
Zygomaticofacial

A - Nasal canthus
B - Temporal 75% of lower lid
C - Temporal canthus and 25% of upper lid

Answer 34

Lacrimal (C)
Infratrochlear (A)
Zygomaticofacial (B)

Question 35

Compare and contrast the structures desensitized by the infraorbital I versus infraorbital II blocks.

Answer 35

(Infraorbital I desensitizes the upper lip and nose, infraorbital II does that and desensitizes the teeth to the 1st molar, the maxillary sinus, the roof of the nasal cavity, and the skin to the medial canthus)

Question 36

What nerve block can be used to desensitize all upper teeth, all of the sinuses, and the nasal cavity?

Answer 36

(Maxillary)

Question 37

What nerve block can be used to desensitize all of the mandibular structures including the cheek teeth and the lateral canthus?

Answer 37

(Mandibular)

Question 38

Compare and contrast the structures desensitized by the mental I versus mental II blocks.

Answer 38

(Mental I desensitizes the lower lip, mental II does that and desensitizes the lower incisors and the 3rd premolar plus everything cranially)

Question 39

What are contraindications for epidurals?

Answer 39

(If there is an infection at the puncture site and +/- sepsis (do not want to introduce bacteria into the dural space), uncorrected hypovolemia (epidural can induce vasodilation and tank the blood pressure further), anticoagulation therapy or bleeding disorders (don’t want to cause an epidural hematoma), and anatomic abnormalities)

Question 40

(T/F) If you are performing a lumbosacral epidural on a horse and get CSF fluid, you should pull out and try again.

Answer 40

(F, give half of what you were planning to give, will still achieve analgesia you just need less volume than if you were in the extradural space)

Question 41

How do you find the site for a lumbosacral epidural/subarachnoid injection?

Answer 41

(Draw a line from the cranial edge of one of the tuber sacrale to the dorsal midline, the L6-S1 space should be 1-2 cm behind that point)

Question 42

How do you find the spot for a caudal epidural?

Answer 42

(Palpate for the first midline depression caudal to the sacrum, that corresponds to the space between Cd1 and Cd2, also can raise and lower the tail and find the first movable coccygeal articulation)

Question 43

What are three ways to determine if you are in the correct space when performing a caudal epidural?

Answer 43

(Use the hanging drop technique, there is lack of resistance to your injection, and there should be a lack of blood/CSF when you aspirate)

Question 44

Which of the epidural options is associated with a higher risk of motor blockade and ataxia?

Answer 44

(Lumbosacral)

Question 45

Why might choosing an alpha 2 agonist not be the best choice if you are using an epidural to provide analgesia primarily?

Answer 45

(They can act systemically when given epidurally (decreased CO, bradycardia, decreased blood pressure))

Question 46

(T/F) The use of opioids for an epidural has minimal effect on the motor nerve blockade, making them an ideal choice for epidural analgesia.

Answer 46

(T with the additional benefits of minimal dose requirements and few side effects)

Question 47

Ketamine provides good somatic/visceral (choose) analgesia.

Answer 47

(Somatic, poor visceral, adding a local anesthetic improves visceral analgesia)

Question 48

Morphine is a great option for an epidural (duration of 6-16 hours, only mild systemic opioid effects in the awake horse (and this is a maybe), and can reduce MAC of halothane) but it does have a slow onset, what drug is typically combined with morphine to gain a faster onset?

Answer 48

(Alpha 2 agonists, you get the faster onset of the alpha 2 (30 minutes) with the prolonged duration of the morphine)

Question 49

When combining an alpha 2 agonist and a local anesthetic for an epidural injection, why should you decrease the dose of the local by 30%?

Answer 49

(Not decreasing the dose could lead to excessive ataxia)