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
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
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
- General w/drawal times:
- Acepromazine
- Mild-moderate calming
- Prolonged effect (2-4 hrs)
- No analgesia
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
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
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
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
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
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)
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
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
- May be more effective in ruminants but serious side effects (after IV administration)
- Atipamazole–~1600:1 sensetivity as dexmedetomidine
- Not usually used in cattle
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
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
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
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
- Adult cattle–at least 24 hrs (26-48), no water for 12-18 hours
- 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
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
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
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
19
Q
What are some various induction techniques (specific drug combos)?
A
- Xylazine IV w/ butorphanol IV, then:
- Thiopental (usually 5% solution) IV
- Be sure catheter is in
- Ketamine (also w/ midazolam or diazepam
- Thiopental (usually 5% solution) IV
-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
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
