Lecture 25: Ruminant Anesthesia (Exam 4) Flashcards
1
Q
What factors determine the approach to a case
A
- Production animal v. pet
- Cost
- Field ax v. in hospital ax
- Standing surgery (sedation + local ax) v. general ax
2
Q
What procedures can the use of just local ax to restrain ruminants be used
A
- Simple diagnostics
- Some sx procedures
3
Q
What type of ax does more complex procedures need
A
General ax
4
Q
What are some anticipated complications of ruminant ax
A
- Hypersalivation
- Bloat
- Hypoventilation
- Regurgitation (potential aspiration pneumonia)
5
Q
Describe hypersalivation
A
Adults produce a lot of saliva
6
Q
Describe bloat
A
Leads to decreased venous return & hypoventilation
7
Q
Describe hypoventilation
A
Dorsal recumbency will worsen the ability to ventilate
8
Q
Describe regurgitation
A
- Active & passive regurgitation potential
- Intubate swiftly & inflate the cuff after induction
- Position the head to promote drainage during ax
- Keep the head elevated w/ the nose pointed down during sedation & recovery
- During ax the head & neck should be positioned to encourage drainage
9
Q
What happens w/ aspiration of acidic stomach/rumen contents
A
- Immediate reflex airway closure
- destruction of type II alveolar cells & pulmonary capillary lining
- Leads to pulmonary edema, hypoxemia, & cyanosis (death in extreme cases)
- Severity depends on the rumen pH & amount of material aspirated (pH in ruminants = 5.5 - 6.5)
- Mechanical airway obstruction can occur depending on food particle size
10
Q
What is recommended in all anesthetized farm animals
A
With holding of food & endotracheal intubation w/ a properly inflated cuff right after placement of ETT
11
Q
Fill out the recommended fasting times
A
12
Q
What does the GI tract of a ruminant < 3 W old function like
A
A simple stomach
13
Q
What does the GI tract of a ruminant > 3 W old function like
A
Functions as a full ruminant
14
Q
Describe fasting of ruminants
A
- helps reserve functional residual capacity since ruminants have a decreased tidal vol compared to horses
- Produces bradycardia in cattle
- Can cause mild metabolic alkalosis
15
Q
Even if precautions are taken as many as what % of adult cattle regurgitate under ax
A
25%
16
Q
Where is an IV catheter place
A
The jugular vein will be accessed easily during sx
17
Q
What gauge catheter should be used
A
- 12 - 14 G on adult cattle
- 16 - 18 g for calves, goats, & sheep
18
Q
Describe acepromazine in LA ax
A
- Not approved for use in food animals by the FDA
- Used at hospitals but not really in other institutions
- May increase the risk of regurgitation
- Do not inject in the coccygeal vein (may hit an artery & slough off tail)
- Contraindicated in hypovolemic or debilitated px
19
Q
Describe Xylazine in LA ax
A
- Not approved for use in food animals by the FDA
- More potent in ruminants
- Goats are most sensitive
- Cattle sensitivity - Brahmans > Herefords > Holsteins
- Stressful envi can cause a prolonged response in cattle
20
Q
What effects does xylazine cause in cattle
A
- Bradycardia
- Rumen atony / bloat
- Hyperglycemia
- Hypoinsulinemia
- Hypoxemia
- Hypercarbia
- Increased urine production
21
Q
What can occur in sheep given xylazine
A
- @ risk for dev pulmonary hemorrhage & edema (leads to hypoxemia)
22
Q
What is not recommended to give sheep
A
alpha 2 agonist
23
Q
What effects does xylazine have on pregnant cattle & sheep
A
- Oxytocin like effect on the uterus
- Premature delivery during last trimester of preg
24
Q
Describe Tolazine for ax
A
- Toxicosis reported in camelids
- Ruminants are also sensitive to tolazoline compared to other species
- Lower doses are recommended
- Avoid IV admin
25
Describe doxapram in LA ax
* Can be somewhat effective in stimulating respiration
* Can reverse alpha 2 sedation
26
Why are anticholinergics typically not used in ruminants
* Salivary secretions become more viscous & could obstruct the airway
* Decrease GI motility & cause bloat
27
Describe benzodiazepines w/ LA ax
* No analgesic effect w/ min sedation
* Typically combined w/ ketamine for induction
* Midazolam & Diazepam
28
What reverses benzodiazepines
Flumazenil
29
Describe opioids can be given for analgesia
* Butorphanol
* Morphine & hydromorphone (not typically used in cattle)
* Buprenorphine (not used in cattle b/c of cost)
30
What is a side effect of opioids
Excitement or vocalization
31
List three induction drugs for LA ax
* Ketamine
* Telazol
* Propofol
32
What is ketamine combined w/ in LA ax
* Benzodiazepin
* GG to make a "double drip"
33
Describe propofol in LA ax
* Smooth induction & recover
* Apnea may occur w/ rapid admin
* Can be used as a CRI for light plane of ax
34
What is ketofol
* Ketamine + propofol IV
* Works well in small ruminants
35
Why should you always intubate a ruminant during ax
* To prevent aspiration of salivary secretions or rumen contents if regurgitation occurs
* Attempting intubation when px is too light may result in regurgitation
36
regurgitation is (more/less) likely to occur if placed in lateral/sternal recumbency while regurgitation is (more/less) likely to occur in dorsal recumbancy
Less; More
37
What size ETT is used in adult cattle, calves, & adult sheep & goats
* Cattle: 20 to 30 mm ID
* Calves: 8 - 12 mm ID
* Sheep & goats: 7 - 12 mm ID
38
Describe intubation in LA
* Hyperextend the head & neck to make an orotracheal axis of 189 degrees
* Blind intubation or w/ hand in adult cattle
* Use laryngoscope & stylet in small ruminants
39
What are the steps of intubation of adult cattle
* Insert a dental speculum
* Manually find the larynx w/ hand
* Insert ET tube btw/ the arytenoids
* Do quickly due to the hand causing airway obstruction
40
When can a small machine be used for the maintenance of ax
* Px < 60 kg
* Using less than 18 mm ETT
41
What are the oxygen flow rates for maintenance of ax
10 - 22 ml/kg/min
42
Fill out the following:
43
What is done for proper positioning of the px
* Padding to prevent myopathy/neuropathy
* Min pressure on the radial nerve
* Support up leg & align parallel to the table
* Head down for saliva or regurgitation to drain out
44
What should be monitored during ax
* HR & pulse quality
* Muscle relaxation
* RR
* CRT / MM
* BP
* Ocular rotation, palpebral reflexes, & pupil size
* Temp
* Arterial blood gases
45
What type of BP monitoring is done for in hospital GA cases
* Direct BP monitoring
* Auricular artery is a good choice b/c the skin is thin
46
Where do we measure indirect BP
* Front leg
* Tail
47
When monitoring what should MAP be above
60 - 70 mgHg
48
Where is ECG leads placed
* In tough hide
* Base apex lead
* Can use 16 g needle to place electordes
49
Describe monitoring ventilation
* Goal: end tidal CO2 btw/ 35 - 45 mmHg
* Ruminants tend to hypoventilate under anesthesia
* Hypocarbia may cause bradycardia in ruminants
50
What should mechanical IPPV be set to
* Tidal volume: 10 - 20 ml/kg
* RR: 6 - 12 bpm
51
Why can the settings for mechanical ventilation be lower than for equine
B/c cows do not have as much fibrous connective tissue in their lungs as horses do
52
What can cause pneumothorax & emphysema
Excissive airway pressure
53
Describe the ocular rotation of ruminants when under ax
* Palpebral reflex disappears w/ light anesthesia
* At induction - eyebally rotates ventrally & cornea obsucred partially by the lower lid
* W/ deepening ax, pupil is completely hidden by the lower lid
* Further increase in depth will lead to dorsal rotation of the eyeball
54
Describe recovery in ruminants
* Leave the ET tube in place until a strong laryngeal reflex returns & the px is able to remain sternal
* Pull the ETT inflated
* Immediately check for away patency after extubation to ensure there is not excessive amounts of fluid (keep the nose pointed down for drainage)
* Check for regurgitation & bloat
55
What is the "sweet smell of ruminant anesthesia success"
Eructation
56
Describe some diff seen in sheep/goats under ax than large ruminants
* Active laryngeal reflexes ( can use topical lidocaine)
* Tend to hypoventilate under ax so anticipate giving IPPV
* Hypothermia can prolong recovery esp in young animals
* Rotationon of the globe does not occur under ax but nystagmus can be seen
