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clinical anesthesia > Farm Animal Anesthesia > Flashcards

Farm Animal Anesthesia Flashcards

1
Q

Why are ruminants not ideal candidates for general anesthesia?
What do we do instead usually?

A

Not ideal because:

  • High risk of regurgitation and aspiration
  • Ruminal tympany
  • Salivation: ruminant cant swallow, therefore saliva can become an aspiration risk or acid-base disturbance
  • Hypoventilation: large rumen/ viscera pushes on the diaphragm
  • Hypotension
  • neuropathy/ myopathy
  • Difficult intubation especially goats and sheep

Usually do Sedation and local blocks instead

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2
Q

How can the risk of aspiration/ regurgitation be reduced in ruminants under general anesthesia?

A
  • Place an endotracheal tube and inflate the cuff
  • Fast the ruminant prior to anesthesia
  • Place a stomach tube to redirect the rumen contents out of the ruminan
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3
Q

How can the risk of ruminal tympany be reduced in ruminants under general anesthesia?

A
  • Fast the ruminant prior to anesthesia
  • Place a stomach tube to redirect the rumen contents out of the cow

note: Trochar + cannula can be used to treat ruminal tympany

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4
Q

How can the risk of salivation be reduced in ruminants under general anesthesia?

A
  • Place an endotracheal tube and inflate the cuff: prevent aspiration
  • Administer LRS + bicarbonate, or collect the saliva and readminister via a stomach tube
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5
Q

How can the risk of hypoventilation be reduced in ruminants under general anesthesia?

A
  • Positive Pressure Ventilation: manual or ventilator

- Fast the ruminant prior to anesthesia: reduce the weight of the viscera on the diaphragm

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6
Q

How can the risk of hypotension be reduced in ruminants under general anesthesia?

A
  • Administer fluids

- May be due to tympany, therefore prevent or treat ruminal tympany

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7
Q

How can the risk of neuropathy/ myopathy be reduced in ruminants under general anesthesia?

A
  • Padding and good positioning of the ruminant
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8
Q

How can you prevent laryngospasm in ruminants while trying to intubate them?

A

Spray Lidocaine (similar to cats)

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9
Q

What induction agents are used in ruminants?

A
  • Ketamine (2-5 mg/kg IV)
    Lower dose used if already premedicated
    Higher dose used if no premed or poor sedation is used

Unlicensed to use but are options:

  • Propofol
  • Alfaxalone
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10
Q

What inhalant anesthetic is used in ruminants?

What is its withdrawal period?

A

Isoflurane

Withdrawal period = 28 days

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11
Q

What Analgesics are available to be used in ruminants?

A

NSAIDs:

  • Carprofen
  • Meloxicam
  • Ketoprofen
  • Flunixin

Local Anesthetics:

  • Procaine + adrenaline: used for cornual nerve blocks
  • Lidocaine: used for epidurals
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12
Q

What is the standard anesthetic protocol used in cattle?

A

Premed: Butorphanol + Xylazine

Induction: Ketamine

Maintenance: Isoflurane

Analgesia: Ketamine CRI, local/ regional blocks, and NSAIDs

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13
Q

What is the standard anesthetic protocol used in sheep/goats?

A

Premed: Butorphanol + Detomidine (not licensed for use in Ireland though)

Induction: Ketamine

Maintenance: Isoflurane

Analgesia: Butorphanol, local/ regional blocks, and NSAIDs

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14
Q

What is the standard anesthetic protocol used for llamas and alpacas?

A

Premed: Xylazine (0.2-0.5 mg/kg) + Butorphanol (0.05-0.5 mg/kg)

Induction: Ketamine

Maintenance: Isoflurane or Sevoflurane

Analgesia: Butorphanol, local/ regional blocks, and NSAIDs

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15
Q

What breeds of pigs are genetically predisposed to Malignant Hyperthermia?

A
  • Landrace
  • Duroc
  • Pietrain
  • Poland-China
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16
Q

Where can an IV catheter be placed in pigs?

A
  • Auricular vein: preferred
  • Cephalic
  • Saphenous
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17
Q

Pigs are prone to laryngospasm, how can this be prevented?

A

Lidocaine spray (similar to cats)

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18
Q

What is Malignant Hyperthermia?

What can trigger this event in pigs?

A

Malignant Hyperthermia is a hereditary disorder of the Ryanodine receptor type 1
This receptor is associated with the calcium channels in the skeletal muscle, leading to excess release of Calcium, intense muscle contraction and the formation of heat

In pigs, this event can be triggered by stress, succinylcholine, volatile agents (including isoflurane) and Nitrous oxide

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19
Q

What are the clinical signs associated with Malignant Hyperthermia in pigs?

A
  • Rapid and sudden Hypercarbia
  • Muscle rigidity = limb extension
  • Retraction of eyeballs
  • Obvious 3rd eyelid protrusion
  • Hot and very pink skin
  • Tachycardia
  • Increased temperature
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20
Q

What is the treatment for Malignant Hyperthermia in pigs?

A

1) Remove the triggering cause e.g. stop isoflurane immediately and give 100% oxygen
2) Cool the body: give cold IV fluids, gastric and bladder lavage + icepacks
3) Dantrolene: is a muscle relaxant

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21
Q

What is a standard anesthetic protocol used in pigs?

A

Premed:

  • Azaperone + Ketamine + Butorphanol = Give IM and leave the animal alone for 30 mins minimum in a quiet environment. Slow recovery too
  • Detomidine + Ketamine + Butorphanol = Give IM
    0. 1 mg/kg, 5mg/kg, 0.2 mg/kg

Induction:

  • Ketamine
  • Thiopentaone

Maintenance: Isoflurane is the drug of choice, but can cause malignant hyperthermia

Analgesia:

  • NSAIDs: Meloxicam or Flunixin
  • Opioid: Butorphanol
  • Local anesthetics
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22
Q

What nerve blocks are indicated in a horn block in cattle?

A

2 or 3 blocks
1) Cornual nerve block: midway b/w lateral canthus and base of horn

2) Cornual branch of the Infratrochlear nerve: b/w medial canthus of eye and base of horn, inject at same level as cornual nerve

+/-

3) Supraorbital branch of Frontal nerve: midway from medial side of horn along the supraorbital process
- note: if you block infratrochlear you are likely to block this one anyway as they are anatomically close together

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23
Q

When are horn blocks indicated for cattle?

A
  • Dehorning/ Disbudding
  • Horn injury
  • Inappropriate horn growth
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24
Q

What local anesthetic cocktail is used for a horn block in cattle?

A
  • 2% lidocaine neat (5-10 mls)
  • Adrenocaine

+ NSAID

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25
Q

What are the complications associated with a horn block in cattle?

A

Block not 100% effective due to:

  • Variations in the nerve path
  • Inaccurate assessment of depth
  • Misplacement of needle
  • Pain on injection might cause the animal to move and misplace the block
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26
Q

When is disbudding/ dehorning usually done in cattle?

A

2 weeks old

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27
Q

When is disbudding/ dehorning of goats usually done?

A

3-5 days old

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28
Q

What are the complications associated with a horn block in goats?

A
  • Overdose is more likely due to reduced ability to metabolize the drug and the goat is so young when disbudding is done
  • Neonate goats are very wriggly and so it is easy to miss

Caution: sedation can be done BUT neonatal goats can easily become hypoglycemic, hypothermic and have depressed respiratory and cardiovascular depression due to their sensitivity to alpha2 agonists

29
Q

What nerve blocks are indicated in a horn block in goats?

A

1) Cornual nerve block: midway b/w lateral canthus and lateral edge of the base of horn
2) Cornual branch of the Infratrochlear nerve: b/w medial canthus of eye and base of horn, inject at same level as cornual nerve

30
Q

What local anesthetic cocktail is used for a horn block in goats?

A

Adult goats:

  • 2% lidocaine neat (2-3 mls)
  • Adrenocaine

+ NSAIDs

Note: neonatal goats will need a reduced dose

31
Q

What is the maximal dose you can use of Lidocaine 2% (neat) in cattle and goats?

A

Cattle: Do NOT exceed 10 mg/kg

Small Ruminants: Do NOT exceed 5mg/kg

32
Q

What blocks can be used to block the eye of a ruminant?

A
  • Peterson Block
  • Retrobulbar block
  • Auriculopalpebral block
33
Q

What cranial nerves does the Peterson Block work on?

A
  • 3: Oculomotor
  • 4: Trochlear
  • 5: Trigeminal
  • 6: Abducens
34
Q

What is the indication of using the Peterson Block on a cow?

A
  • Enucleation surgery
  • Foreign body removal
  • Surgery of the eyelids (e.g. mass removal) is possible if combined with auriculopalpebral block and eyelid block
35
Q

The Peterson Block does NOT anesthetize the __________

A

Eyelids

Therefore, an auriculopalpebral block is needed to stop motor function to the eyelids, and an eyelid block is needed to stop sensory function

36
Q

What anesthetic is used in the Peterson Block?

A

10-15mL of 2% Lidocaine

37
Q

What are the advantages of using the Peterson Block?

A
  • Safer than the Retrobulbar block as there is less risk of globe penetration and hemorrhage
  • Less likely to inject into the meninges surrounding the optic nerve which is considered fatal
  • Less edema and inflammation, than with infiltration of local anesthetic into the eyelids and orbit
38
Q

What is the disadvantage of using the Peterson Block?

A
  • Its technically more challenging to perform than other blocks anesthetizing the same/ similar area
39
Q

What is the use of the 1 point Retrobulbar block?

A
  • Enucleation
40
Q

What is the advantage of using the 1 point Retrobulbar block?

A
  • Provides excellent peri-operative analgesia
41
Q

What is the disadvantage of using the 1 point Retrobulbar block?

A
  • Accidental injection of local anesthetic into a blood vessel could be fatal
  • Accidental injection of local anesthetic agent into the CSF surrounding the optic nerve could be fatal
  • There is a greater risk of globe trauma if performed incorrectly, this is particularly problematic especially if an infection is present
  • There is a risk of trauma to local tissues
  • There is the risk of initiating the oculocardiac reflex
42
Q

What is the use of the 4 point Retrobulbar block?

A
  • Enucleation
43
Q

What is the advantage of using the 4 point Retrobulbar block?

A
  • Provides excellent peri-operative analgesia
44
Q

What is the disadvantage of using the 4 point Retrobulbar block?

A
  • Accidental injection of local anesthetic into a blood vessel could be fatal
  • Accidental injection of local anesthetic agent into the CSF surrounding the optic nerve could be fatal
  • There is a greater risk of globe trauma if performed incorrectly, this is particularly problematic especially if an infection is present
  • There is a risk of trauma to local tissues
  • There is the risk of initiating the oculocardiac reflex
45
Q

What is the use of the Auriculopalpebral nerve block?

A
  • To allow for examination of the eye especially in painful conditions
  • To control eyelid movement during minor surgical procedures
46
Q

What is the advantage of using the Auriculopalpebral nerve block?

A
  • Provides excellent eyelid paralysis

- Can be used in conjunction with sedation and other regional blocks

47
Q

What is the disadvantage of using the Auriculopalpebral nerve block?

A
  • Only blocks motor, NOT sensory function

- The supraorbital, lacrimal, infratrochlear and zygomatic nerves require blocking to remove all periocular sensation

48
Q

Describe the notch location used as a landmark for the Peterson Block

A

Notch is formed:

  • Cranially by the supraorbital process
  • Ventrally by the zygomatic arch
  • Caudally by the coronoid process of the mandible
49
Q

Describe the locations used in the 4 point Retrobulbar block

A
  • Upper and lower lids (12 and 6 o’clock position)
  • Lateral and medial canthi (3 and 9 o’clock position)

note: use your finger to create a space between the globe and the orbit

50
Q

Describe the location of the auriculopalpebral block

A
  • Insert the needle at the dorsal border of the zygomatic arch, in front of the base of the ear
51
Q

What is the oculocardiac reflex?

A

The oculocardiac reflex is a phenomenon where a decrease in pulse rate is associated with traction applied to extraocular muscles and/or compression of the eyeball

52
Q

You want to perform a Line Block, what anesthetic agent is used and why?

A

2% Lidocaine (neat)

- Avoid using any mixture with adrenaline as it can cause local tissue ischemia and necrosis of the skin and muscle

53
Q

You want to perform an abdominal procedure on a cow (e.g. C-section), what blocks can be used?

A

1) Line block of the skin
2) Paravertebral blocks of T13, L1 and L2 +/- L3 and L4
3) Inverted L Block

54
Q

What are the 2 techniques used in the Paravertebral blocks

A

1) Proximal paravertebral block
2) Distal paravertebral block

Note: They achieve the same thing, they just have different advantages and disadvantages

Note:

  • They will desensitize the entire body wall including the peritoneum, and provide muscle relaxation
  • Indicated for Rumenotomy, Abomasal, cecal surgeries and exploratory laparotomies as well as C-sections
55
Q

Describe the Proximal paravertebral block

A

Needle: 18G, inserted 10-15cm deep

Placement: caudal to the transverse processes of T13, L1 and L2

  • Needle is placed through the skin at the anterior edge of the transverse process of L1 (4cm lateral to the dorsal midline)
  • The needle is passed ventrally until it contacts the transverse process of L1
  • Needle is walked off the cranial edge of the transverse process of L1 and advanced 1cm
  • 6-8 mls is injected (desensitized the ventral branch)
  • Needle is withdrawn just dorsal to the transverse process and 6-8mls in injected (desensitized the dorsal branch

The above steps are repeated for the anterior edge of the transverse process L2 and L3 to block spinal nerves T13, L1 and L2

56
Q

What are the advantages and disadvantages of the Proximal paravertebral block?

A

Advantages:

  • simple and quick
  • small doses of anesthetic are used
  • wide and uniform area of analgesia is obtained
  • no anesthetic is at the surgical site and thus less chance of edema

Disadvantages:

  • can cause the spine to bend away from the incision, making closure more difficult
  • difficult to perform in obese or muscled animals
57
Q

How can you tell if your paravertebral block was effective/ placed correctly?

A
  • Skin will become hyperemic and warm due to vasodilation
  • Spine may curve slightly
  • Pinch test for sensation using forceps
58
Q

Why might the spine curve during a paravertebral nerve block?

A

Relaxation of the epaxial musculature on the affected side, the spine will curve towards the opposite side

59
Q

Describe the Distal paravertebral block

A

Needle: 3.5-5.5cm long needle

Placement: anesthetic is placed above and below the ends of the transverse processes of L1, L2 and L4, which desensitizes spinal nerves T13, L1 and L3

  • Needle is inserted ventral to the transverse process of L1 (blocking T13 nerve), 5mLs of 2% Lidocaine is injected
  • Pull out 50% of the way and redirect dorsally, then inject the remaining 5mls

Repeat for transverse processes of L2 and L4 (blocking spinal nerves L1 and L3 respectively)

60
Q

What are the advantages and disadvantages of the Distal paravertebral block?

A

Advantages:

  • Won’t get spinal curve (scoliosis)
  • Easier
  • More consistent results

Disadvantages:

  • Larger doses of Lidocaine are needed
  • Variations of efficacy can occur due to variation in anatomic pathways of the nerves
61
Q

When is a Caudal Epidural indicated?

A
  • Obstetrics
  • Surgical procedures involving:
    Tail
    Perineum
    Anus
    Rectum
    Vulva and Vagina
    Prepuce and Scrotum
62
Q

Where are the 2 main locations for a caudal epidural in a ruminant?

A
  • Sacrococcygeal space (S4-Co1)

- First Intercoccygeal space (Co1-Co2

63
Q

Which anesthetic agents can be used for a caudal epidural?
How much of each agent can be used?
What needle size and length is used?

A

Lidocaine 2%: 0.5mLs for every 45kg of bodyweight

+/- Xylazine 2%: 0.05 - 0.07 mg/kg

  • Xylazine has a 20 min onset, and a duration of action up to 6 hours
  • The addition of xylazine is particularly helpful in obstetrics, and used in conjunction with an intratesticular lidocaine block

18G needle (3.8cm long)

64
Q

Describe the technique of a caudal epidural?

A

Same for a Lumbosacral epidural

  • Advance needle perpendicular to the skin surface
  • Place a drop of agent on the hub of the needle
  • Advance needle slowly until anesthetic solution is drawn into the epidural space due to negative pressure
  • Attach the syringe
  • Inject slowly (keeping an air bubble in the syringe will help determine if you are in the right tissue)
65
Q

What are the indications for using Intravenous Regional Anesthesia (IVRA) in cattle?

A
  • Surgery of the distal limb + digits
66
Q

What anesthetic agent is used for Intravenous Regional Anesthesia (IVRA) in cattle?

A
  • Lidocaine 2% (neat): usually 20mls is used, takes 15-20 mins to take effect
    caution: do not use a mixture containing adrenaline, as this will cause devitalization of the tissue and tissue necrosis
67
Q

Describe Intravenous Regional Anesthesia (IVRA) used in cattle

A
  • Apply tourniquet proximal to the injection site
  • Insert needle or catheter into the chosen vein
  • Aspirate to confirm correct needle location
  • Inject into the superficial vein
68
Q

What are the advantages and disadvantages of using Intravenous Regional Anesthesia (IVRA) in cattle?

A

Advantages:

  • simple
  • rapid onset and recovery
  • single injection site
  • minimal blood in surgical field
  • may also administer antibiotics into site

Disadvantages:

  • lateral recumbency often is needed
  • hematoma formation may occur at the site of the injection
  • damage to the nerve underneath the tourniquet is possible
  • may get local anesthetic toxicity when the tourniquet is released
69
Q

What are the contraindications of using an epidural?

A
  • Septicemia
  • Skin infection at the site of the epidural
  • Coagulopathies
  • Known hypersensitivity to agent

clinical anesthesia (17 decks)

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