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Anesthesiology > Ruminant anesthesia > Flashcards

Ruminant anesthesia Flashcards

1
Q

T/F: In general, ruminants are amenable to physical restraint that will allow procedures to be done standing (or laying down) without anesthesia or sedation

A

TRUE

Time must be at a minimum when laying down

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2
Q

T/F: Very few ruminant surgical procedures can be performed standing using local anesthetic techniques

A

FALSE–Many surgical procedures can be erformed standing using local anesthetic techniques

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3
Q

What are some general concepts regarding ruminant anesthesia? Give an example drug

A
  • Often mild sedation (standing) reduces stress and helps facilitate surgeries and adds some central anesthesia
  • Most drugs are not approved for food animal use
    • General w/drawal times:
      • Milk = at least 3 days
      • Meat = at least 7 days
  • Acepromazine
    • Mild-moderate calming
    • Prolonged effect (2-4 hrs)
    • No analgesia
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4
Q

General concerns (risks)?

A
  • Anesthesia/recumbency in large ruminants often considered high risk
    • If they weren’t fasted
    • Recumbent sedation w/o airway protection
      • Inability to eructate normally–bloat, tympany
      • Regurg, aspiration,…
      • Inability to ventilate and oxygenate well due to large abdominal volume
    • IF they go down, must get them sternal–difficult in very large bovine
    • If down long–myositis/neuritis
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5
Q

Sedation protocols–general (how to decide what to use)

A
  • Look in the books–dif. options
  • People use what they are comfortable with from experience; there can be conflicting opinions, difference options
  • Most important to understand which drugs are commonly used
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6
Q

Xylazine

A
  • Ruminants are the most sensitive species to the effects of xylazine with breed sensitivity differences
    • Goats (most sensitive) > bovine (brahman > hereford > holsteins) > sheep >> equine >> swine (most resistant)
    • Cattle–1/10 dose of equine
  • Effects in cattle can be variable–may become recumbent at very low doses
    • Can be unpredictable
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7
Q

Things to remember about alpha2 agonists (6)

A
  • Xylazine produces uterine contraction–oxytocin effect
    • Poss. abortion in bovine and shee (but NOT equine)
  • Detomidine is NOT abortifacient in bovine, and dosage in equine and bovine are similar
    • Detomidine more specific to alpha2 than xylazine
  • C/V depression, some resp. depression
  • GI effects: dec. motility, rumen atony and bloat
  • Xylazine produces hyperglycemia (hypoinsulinemia) in cattle and shee
  • Sheep–avoid xylazine
    • ​Hypoxemia
    • Assoc. pulmonary edema
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8
Q

General statements about anesthetics (review):

Acepromazine

Alpha2 agonists

Benzodiazepines

Opioids

A
  • Ace
    • Effective to ‘take edge off’
    • Would not be expected to produce profound (recumbency) sedation
    • May/may not produce desired effect–dose-dependent duration and effect
      • Do not use in debilitated/ill animals
  • Alpha2 agonists
    • Can produce profound sedation
    • Side effects
    • Do not use in debilitated animals
  • Benzodiazepines
    • Small and young ruminants–can be sedated, esp. if used w/ an opioid
    • Avoid in large ruminants (ataxia) unless used with induction
    • Always good choice to use as part of any induction
  • Opioids
    • Profound depressant effect on GI tract
    • Can improve sedation w/ a tranquilizer
    • Usually never used alone
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9
Q

Standing sedation (bovine) example?

A
  • Xylazine
    • Low-end IV if calm
    • IM if anxious/unruly
  • Detomidine
    • IV or IM
  • Add butorphanol IV–can dec. dose of xylazine
  • ALWAYS use 20mg/ml xylazine (NOT 100mg/ml)
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10
Q

Example: 2 month-old calf requires radiographs of head (trauma)–duration estimated ~30 min.

Drugs/procedure?

A
  • Young calf–sedated w/ 0.1mg/kg xylazine IM
  • Recumbency and profound sedation for rads of head
  • Young calf, fasted = less risk for regurg
    • Still somewhat of a risk
    • May/may not intubate
  • End of procedure
    • Reverse with atipamazole or tolazaline
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11
Q

Alpha2 reversal agents

A
  • Yohimbine–similar alpha2:alpha1 sensitivity as xylazine
    • Efficacy in cattle varies and sometimes is relatively ineffective
  • Tolazoline–non-selective alpha receptor antagonist
    • May be more effective in ruminants but serious side effects (after IV administration)
      • Bradycardia, tachycardia, hypotension, cardiac asystole, seizures (llamas)
    • Use low dosage IM for slow onset
      • If you must, 1/2 dose well-diluted slowly IV
  • Atipamazole–~1600:1 sensetivity as dexmedetomidine
    • Not usually used in cattle
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12
Q

Examples of procedures that use standing anesthesia

A
  • Enucleation
  • Dehorning
  • Caudal epidural
  • Obstetric procedures and rectal tenesmus
  • Standing procedures for laparotmy, rumenotomy, celiotomy, C-section, ovariectomy, correction of GI displacement
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13
Q

Example: 3yo heifer–400kg displaced abomasum; fiesty, resisting local blocks

Drugs/procedure?

A
  • Sedation required (fiesty, resistant)
  • Xylazine IM
    • Expecting 30-60 min, ~30 standing restraint
  • Distal paravertebral thoracolumbar block–performed using lidocaine
  • Still sedated at end of surgery–> reversal planned
    • Yohimbine or tolazaline IM
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14
Q

When is general anesthesia required?

A
  • More extensive or prolonged procedures; dorsal recumbency necessary
  • High risk in large ruminants but can be done safely
    • Adequate fasting
    • Attn to avoid potential problems of regurg and aspiration
    • Secure airway
    • Attn to proper positioning and padding–avoid nerve/muscle injury
  • The process of laying down/anesthetizing a large ruminant can depend on the physical layout of the hospital/equipment/personnel and temperament of the animal
  • If tractable–can be walked into induction area–near wall/induction gate–for induction
    • Or kept in stock w/ head secured (as for catheter placement) induction can take place in stock; fall to sternal, intubated–kept asleep–moved via hoist to surgery
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15
Q

What’s involved in preparing for GA?

A
  • Fasting
    • Adult cattle–at least 24 hrs (26-48), no water for 12-18 hours
      • Bradycardia common (vagal effect of the fast)
      • Anticholinergics–NOT routinely given–dec. GI motility, produce bloat
    • Calves, sheep, goats–12-18 hrs, no water 8-12
  • Laboratory evaluation–depends on physical condition, economics, but should include at least ‘big 4’
  • IV catheter must be secured–jugular
    • Adults–10ga, 14ga, 5.5 in
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16
Q

Proper catheter size?

Fluids?

A
  • Adult cattle–large 10ga x 5.5 in catheter (or 14ga–nothing smaller)
    • Too short will be dislodged
    • Too small–can’t get fluids in fast enough if needed
  • Tough hide–need small cut down
  • Fluid rates: 5-10 ml/kg/hr to start
  • Small ruminants–14ga, 5 in.
    • Unless pigmy or neonate
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17
Q

Sedation/pre-med protocols–bovine

A
  • Acepromazine IM if intractable
    • Acep–IM–takes at least 30 min effect
  • Xylazine–IV or IM
  • Detomidine–IV or IM
  • Butorphanol–to allow lower doses of xylazine
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18
Q

T/F: In bovine, premedication may or may not be necessary

A

TRUE

If tractable, may walk to induction room–so sedative drugs become part of induction

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19
Q

What are some various induction techniques (specific drug combos)?

A
  • Xylazine IV w/ butorphanol IV, then:
    1. Thiopental (usually 5% solution) IV
      1. Be sure catheter is in
    2. Ketamine (also w/ midazolam or diazepam

-OR-

  • Xylazine IV w/ butorphanol IV, then:
    • Guafenesin 5% immediately followed by #1 or #2
    • Propofol or alfaxalone–only in very small ruminants–too expensive for large ruminants
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20
Q

Guaifenesin (GG)

What is it?

Why is it given?

Side effects?

Solution percentage?

Dose?

A
  • GG 5% centrally acting muscle relaxant
    • No/very little sedation
    • No analgesia
  • To improve quality of induction
    • Relaxation
    • Reduces dosage rate of anesthetic
  • No/little cardiovascular or respiratory depression unless very high dosages
  • 5% solution in 1 liter of 5% dextrose/water (or in 500 ml)
  • Dosage to effect until animal is ataxic–usually ~40-80mg/kg
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21
Q

Inductions with GG–4 options

A
  1. After xylazine + butorphanol
    1. GG 5% in 500ml dextrose/water
    2. Give GG as fast as possible
    3. Given to effect until animal is ataxic
    4. Follow with
      1. Thiopental IV or ketamine IV (w/ or w/o diazepam or midazolam IV)
      2. Give, expect ~1-2mg/kg
  2. After xylazine + butorphanol
    1. GG 5% in 500ml of 5% dextrose/water
    2. Add to 500ml 5% GG 500ml ketamine ‘double drip’
  3. To #2, add 50mg xylazine ‘triple drip’
    1. Because of sensitivity to xylazine in ruminants most people only use ‘double drip’
  4. After xylazine/butorphanol
    1. Add to GG 5%
      1. 2gm thiopental to GG-and give to effect-at ~1-2mg/kg
22
Q

GG–advantages/disadvantages?

A
  • Advantages
    • Little/no cardiovascular or res. depression
    • Reduce amount of induction drugs
    • Very good relaxation (GG used to be cheap)
  • Disadvantages
    • Slower induction–large amount of volume to administer so must have good control over the animal (i.e. swing gate, in stocks, etc.)
  • Always keep sternal once down until intubated
23
Q

What should you start with when intubating?

A

Mouth gag (speculum)

24
Q

Intubation: large bovine

A
  • Pass arm into oral cavity
  • Manually reflect epiglottis down
  • Guide the tube into the larynx between the aryetenoid cartilages into the trachea
  • Bovine must not be too light–gag/regurg
  • Cuff must be inflated while animal is still sternal
  • Tube size 24-30mm id
25
Q

Padding and positioning

Complications?

Equipment?

Different positioning?

Legs?

Eyes?

A
  • Post-anesthetic myopathy and neuropathy–feared complication in LA
  • Padded table–thick foam pads, water beds
    • With attn to positioning
  • Lateral–dependent foreleg pulled forward, other legs perpendicular to body and parallel to table
    • Avoid brachial plexus injury
  • If poss., have nose lower than laryngeal area (drainage of saliva and rumen fluid)
  • Dorsal recumbency–body needs to be balanced evenly on the back w/ even pressure on the gluteals
  • All legs should be flexed and relaxed
  • Always protect eyes (lubricate) from excessive pressure or drainage fluids
26
Q

What 5 things are included in maintenance of bovine?

A
  • Begin O2 flows (20-50ml/kg) ~5-7 L/min isoflurane
    • Start at 2-4% until eyes show stage 3, plane 2
  • Maintain O2 flow ~10ml/kg w/ iso 1.5-2%
    • Depends on individual
    • Sevo too expensive
  • Balanced electrolyte solution 10ml/kg/hr–then dec. rate to 5ml/kg
  • Intra-op butorphanol–0.5mg/kg for additional analgesia
  • Always have extra drugs available
    • ​Ketamine, GG, thiopental (if animal gets very light)
27
Q

What 9 things are involved in monitoring of bovine during anesthesia?

A
  • Auricular artery–for direct BP monitoring and blood gas analysis
  • ECG–hide is thick–attach ECG clip to a needle passed through hide
  • Indirect BP in very large bovines–not option
    • Maybe doppler on tail for trends/sound
  • Pulse oximetery; ETCO2
  • Eye signs–rolled eyeball, lack of palpebral reflex
  • Lack of swallow
  • Bovines will hypoventilate and develop V/Q mismatch in relatively short time (<1hr)
    • Must be mechanically ventilated
  • Keep ETCO2 <55-60
    • Blood gas if poss. to determine PaCO2-ETCO2 diff.
  • SPO2; PaO2 if poss.
28
Q

Supportive care

Head position

Cuff

Rumen tube

Anticholinergics

A
  • Ruminants will produce copious amounts of saliva and rumen fluid during a procedure–try to position head in a declined plane (not always poss.–dorsal)
  • Be certain the cuff is well inflated!
  • Rumen tube helps to prevent bloat and avoid aspiration of the fluid that could accumulate
  • Anticholinergics will NOT decrease saliva volume–only make it more viscous
    • Do not use unless necessary to treat bradycardia
    • Decrease intestinal motility
  • Check electrolytes, blood gas if long ax
    • Rare that fluid/bicarb loss will cause problems
29
Q

Monitoring bovine

HR?

Ventilation?

PaCO2?

BP?

Large bovines?

A
  • HR should be ~60-80bpm in large bovine
  • Ventilate ~10ml/kg tidal volume at RR ~8-10 bpm
  • Maintain PaCO2 <55-60mmHg
  • Keep mean BP >70mmHg
  • Large bovines often will have inc. BP during sx–not necessarily due to inadequate anesthesia (mech. not well defined)
30
Q

5 steps in bovine recovery?

A
  • Keep bovine aslee and intubated as he is moved to his stall
    • Keep ketamine/GG handy if he gets too light (esp. if hoisting is necessary)
  • Unlike horses, cattle recover well and calmly and do not make premature efforts to stand
  • Use hay bales/wall and mult. people to maintain sternal recumbency
  • Keep intubated until swallowing
  • Keep close watch until he can maintain himself sternal
  • When ready, encourage standing to ensure no nerve/muscle damage has occurred
31
Q

Small ruminants

Various procedures requiring anesthesia?

A
  • Castration
  • Umbilical hernia
  • Intestinal obstructions
  • Obstructive urolithiasis (goats)
  • Dehorning
  • Fracture repairs
32
Q

What drug should you be extra careful with when dehorning goats?

33
Q

Small ruminant anesthesia

Preparation

A
  • Neonates (calves) should not be fasted
    • To avoid hypoglycemia
  • Calves (essentially monogastric) ~1mo: fasting 2-4hrs
  • Young bovine, sheep, goats
    • Fast 12-18hrs, water ok
  • Good physical exam auscultation heart and lungs
  • Economics and general health determines lab work
    • At least ‘big 4’
    • If ill include chemistries
34
Q

Small animal anesthesia:

Sedation/premedication

A
  • Sheep/goats/young calves can be sedated w/ benzodiazepines with/without butorphanol
    • Xylazine usually not necessary
    • Midazolam IV w/ butorphanol IV
  • Acepromazine IM + morphine IM
  • In unruly calves/goats–xylazine IM
    • Remember goat sensitivity
  • Avoid xylazine and/or acepromazine in hypovolemic or very ill animals
35
Q

Small ruminant anesthesia

Xylazine–sheep

A
  • EXTREME CAUTION (and other alpha2’s)
  • Impairment of gas exchange due to alveolar edema
  • Absence of a free radical mediated inflammatory mechanism
    • Thought to be increased pulmonary vascular resistance–inc. alveolar pressures and alveolar edema–vasoconstriction pulmonary vasculature
36
Q

Small ruminant anesthesia

Ex: 5mo old calf umbilical hernia (calf doesn’t want to stand still): drugs/protocol?

A
  • Fasted–no food 12-18hrs
    • No water 8-12hrs
  • Not wanting to stand still –> give xylazine IV
  • Then midazolam w/ butorphanol IV (good sedation)
    • Induction: ketamine OR ketamine + propofol (ketafol)
37
Q

Small ruminant anesthesia

Intubation

A
  • Calves and small ruminants
    • Must visualize–use laryngoscope w/ stylet
  • Sheep/goats
    • Narrow mouth–difficult to open wide
      • Use gauze/ties to open
      • Do not attempt if too light
      • Stylet necessary
  • Pass stylet through arytenoids–then slide in the T tube over the catheter
  • Advance T tube while pulling out stylet
  • Always keep sternal until cuff is inflated
  • Note–O2 high flow at nostril
38
Q

Small ruminant anesthesia

T tube sizes

A
  • 20-30kg = 7-10mm id
  • 30-40kg = 10-11
  • >40-50kg = 12
  • Verify proper tracheal placement
    • ETCO2
    • Condensation in tube when breathing
  • Keep sternal–inflate cuff
  • Move to surgery table
39
Q

Small ruminant anesthesia

Maintenance

A
  • O2 flow 30-50ml/kg
  • Isoflurane
    • Begin 2-3% until loss of palpebral
    • See deviated eyeball–then decrease vaporizer ~1.5-2%
  • Fluids–begin 10ml/kg/hr
    • Neonates add dextrose–2.5-5% in fluids
  • ECG, BP, ETCO2, SPO2
40
Q

Small ruminant anesthesia

Calves/small ruminants: ideal

HR

BP

Ventilation problem?

ETCO2

Doppler

A
  • HR = 80-120bpm
  • BP
    • Systolic 90-120 (doppler)
    • Diastolic 60-80
    • Mean 75-100
  • Ruminants will hypoventilate
  • Maintain ETCO2 <55 mmHg
  • Doppler–pressure at median artery
41
Q

Small ruminant anesthesia–monitoring

SPO2/HR/BP/mean?

Ventilation?

Lung CT?

Avoid?

A
  • SPO2 = 96%, HR = 110, BP = 100/46, mean = 65
  • Take care in ventilating sheep and other ruminants
  • Lung CT not as fibrinous in sheep/other ruminants as in horses
    • Excessive positive pressure may produce injury
    • Pneumothorax
  • Avoid high airway pressures (not much > 15cm H2O)
    • Positive pressure ventilation dec. venous return and BP
42
Q

Small ruminant anesthesia

Where do you put the arterial catheter?

43
Q

Small ruminant anesthesia

Recovery

A
  • Wash mouth (if regurgitated) before extubation
  • Extubate when swallowing/chewing
  • Pull tube w/ cuff inflated
    • Esp. if regurg occurred–to ‘pull out’ debris around larynx
  • Keep warm
  • Usually calm recoveries
44
Q

Small ruminant anesthesia

Analgesia

A
  • Flunixin
  • Buprenorphine IV
  • If received xylazine and still depressed consider reversal
    • Atipamazole IM ideally or dilute very slow IV to effect
    • ​Tolazaline IM
45
Q

Camelids

Stomach?

Fasting?

Jugular groove?

Which jugular?

A
  • Stomach divided into 3 compartments
    • Also susceptible to tympany, regurg, and aspiration
  • Similar fasting times to sheep and goats–12-18hrs no food, no water 8-12hrs
  • Camelids do not have a jugular groove–jugular vein lies deep to the muscles (cranially) superficial to the carotid artery and vagosympathetic trunk
  • Use right jugular–to avoid esophagus
46
Q

Camelids

Venous access/catheterization–advantages vs. disadvantages for different sites

A
  • High
    • Adv–less apt to hit the artery–omohyoideus m. lies between artery and the vein
    • Dis–skin much thicker and mvt of head interferes
  • Low
    • Adv–bony landmarks of the 5-6th vertebral processes for location; jugular easier to distend; skin is thinner
    • Dis–no protection from carotid
47
Q

Camelids

Premedication

A
  • Not as sensitive to alpha2 agonists as other ruminants
    • Cattle > camelids > horses (more sensitive to less sensitive)
      • Llamas more sensitive than alpacas
    • Cardiovascular effects of the alpha2 similar
  • Xylazine IV
    • Dif. doses = w/ w/o recumbency
      • Higher = 20-30 min w/ recumbency
48
Q

Llamas/alpacas

Short injectable anesthesia (specific)

A
  • Xylazine/ketamine
    • Xylazine IV + ketamine IV or IM
    • IM = induction 10 min
    • Duration = 30-60 min
49
Q

Llamas, alpacas

Most widely used protocol for field settings?

A

Combination of xylazine, ketamine, and butorphanol (all IV); ~20-40 min recumbency

50
Q

Llamas/alpacas

Induction/intubation

A
  • Similar as done with sheep and goats
  • Propofol
    • OR ketamine + midazolam
    • OR ketofol
  • Intubation–similar to sheep and goats–keep sternal, extend neck
    • Long blade, laryngeal scope, long stylet
    • Conventional small animal machines in ruminants; camelids <60kg
51
Q

Llamas/alpacas

Maintenance

A
  • Usually ventilate better than cattle
    • Still IPPV necessary to keep PaCO2 < 55mmHg
  • Monitoring similar as with all ruminants
  • Proper padding and positioning important
52
Q

Llamas/alpacas

Recovery

A
  • General recover well–w/o emergence delerium
    • Don’t try to stand too early
  • Extubate when swallowing–phenylephrine in the nares before recovery (reduce nasal edema)
    • Obligate nose breather–assure good air flow for recovery
    • Place nasal-tracheal tube if necessary
  • Support head during recovery

Anesthesiology (16 decks)

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