Ruminant anesthesia Flashcards
(52 cards)
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
21
Q
Inductions with GG–4 options
A
- After xylazine + butorphanol
- GG 5% in 500ml dextrose/water
- Give GG as fast as possible
- Given to effect until animal is ataxic
- Follow with
- Thiopental IV or ketamine IV (w/ or w/o diazepam or midazolam IV)
- Give, expect ~1-2mg/kg
- After xylazine + butorphanol
- GG 5% in 500ml of 5% dextrose/water
- Add to 500ml 5% GG 500ml ketamine ‘double drip’
- To #2, add 50mg xylazine ‘triple drip’
- Because of sensitivity to xylazine in ruminants most people only use ‘double drip’
- After xylazine/butorphanol
- Add to GG 5%
- 2gm thiopental to GG-and give to effect-at ~1-2mg/kg
- Add to GG 5%
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
**Padding and positioning**
Complications?
Equipment?
Different positioning?
Legs?
Eyes?
* 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
What 5 things are included in maintenance of bovine?
* 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
What 9 things are involved in monitoring of bovine during anesthesia?
* 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
**Supportive care**
Head position
Cuff
Rumen tube
Anticholinergics
* 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
**Monitoring bovine**
HR?
Ventilation?
PaCO2?
BP?
Large bovines?
* 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
5 steps in bovine recovery?
* 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
**Small ruminants**
Various procedures requiring anesthesia?
* Castration
* Umbilical hernia
* Intestinal obstructions
* Obstructive urolithiasis (goats)
* Dehorning
* Fracture repairs
32
What drug should you be extra careful with when dehorning goats?
Lidocaine
33
**Small ruminant anesthesia**
Preparation
* 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
**Small animal anesthesia:**
Sedation/premedication
* 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
**Small ruminant anesthesia**
Xylazine--sheep
* **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
**Small ruminant anesthesia**
Ex: 5mo old calf umbilical hernia (calf doesn't want to stand still): drugs/protocol?
* 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
**Small ruminant anesthesia**
Intubation
* 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
**Small ruminant anesthesia**
T tube sizes
* 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
**Small ruminant anesthesia**
Maintenance
* 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
**Small ruminant anesthesia**
Calves/small ruminants: ideal
HR
BP
Ventilation problem?
ETCO2
Doppler
* 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
**Small ruminant anesthesia****--monitoring**
SPO2/HR/BP/mean?
Ventilation?
Lung CT?
Avoid?
* 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
**Small ruminant anesthesia**
Where do you put the arterial catheter?
Ear
43
**Small ruminant anesthesia**
Recovery
* 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
**Small ruminant anesthesia**
Analgesia
* Flunixin
* Buprenorphine IV
* If received xylazine and still depressed consider reversal
* Atipamazole IM ideally or dilute _very slow IV to effect_
* **__**Tolazaline IM
45
**Camelids**
Stomach?
Fasting?
Jugular groove?
Which jugular?
* 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
**Camelids**
Venous access/catheterization--advantages vs. disadvantages for different sites
* 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
**Camelids**
Premedication
* 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
**Llamas/alpacas**
Short injectable anesthesia (specific)
* Xylazine/ketamine
* Xylazine IV + ketamine IV or IM
* IM = induction 10 min
* Duration = 30-60 min
49
**Llamas, alpacas**
Most widely used protocol for field settings?
Combination of xylazine, ketamine, and butorphanol (all IV); ~20-40 min recumbency
50
**Llamas/alpacas**
Induction/intubation
* 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
**Llamas/alpacas**
Maintenance
* Usually ventilate better than cattle
* Still IPPV necessary to keep PaCO2 \< 55mmHg
* Monitoring similar as with all ruminants
* Proper padding and positioning important
52
**Llamas/alpacas**
Recovery
* 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
