Lecture 25: Ruminant Anesthesia (Exam 4) Flashcards
What factors determine the approach to a case
- Production animal v. pet
- Cost
- Field ax v. in hospital ax
- Standing surgery (sedation + local ax) v. general ax
What procedures can the use of just local ax to restrain ruminants be used
- Simple diagnostics
- Some sx procedures
What type of ax does more complex procedures need
General ax
What are some anticipated complications of ruminant ax
- Hypersalivation
- Bloat
- Hypoventilation
- Regurgitation (potential aspiration pneumonia)
Describe hypersalivation
Adults produce a lot of saliva
Describe bloat
Leads to decreased venous return & hypoventilation
Describe hypoventilation
Dorsal recumbency will worsen the ability to ventilate
Describe regurgitation
- 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
What happens w/ aspiration of acidic stomach/rumen contents
- 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
What is recommended in all anesthetized farm animals
With holding of food & endotracheal intubation w/ a properly inflated cuff right after placement of ETT
Fill out the recommended fasting times
What does the GI tract of a ruminant < 3 W old function like
A simple stomach
What does the GI tract of a ruminant > 3 W old function like
Functions as a full ruminant
Describe fasting of ruminants
- helps reserve functional residual capacity since ruminants have a decreased tidal vol compared to horses
- Produces bradycardia in cattle
- Can cause mild metabolic alkalosis
Even if precautions are taken as many as what % of adult cattle regurgitate under ax
25%
Where is an IV catheter place
The jugular vein will be accessed easily during sx
What gauge catheter should be used
- 12 - 14 G on adult cattle
- 16 - 18 g for calves, goats, & sheep
Describe acepromazine in LA ax
- 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
Describe Xylazine in LA ax
- 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
What effects does xylazine cause in cattle
- Bradycardia
- Rumen atony / bloat
- Hyperglycemia
- Hypoinsulinemia
- Hypoxemia
- Hypercarbia
- Increased urine production
What can occur in sheep given xylazine
- @ risk for dev pulmonary hemorrhage & edema (leads to hypoxemia)
What is not recommended to give sheep
alpha 2 agonist
What effects does xylazine have on pregnant cattle & sheep
- Oxytocin like effect on the uterus
- Premature delivery during last trimester of preg
Describe Tolazine for ax
- Toxicosis reported in camelids
- Ruminants are also sensitive to tolazoline compared to other species
- Lower doses are recommended
- Avoid IV admin
Describe doxapram in LA ax
- Can be somewhat effective in stimulating respiration
- Can reverse alpha 2 sedation
Why are anticholinergics typically not used in ruminants
- Salivary secretions become more viscous & could obstruct the airway
- Decrease GI motility & cause bloat
Describe benzodiazepines w/ LA ax
- No analgesic effect w/ min sedation
- Typically combined w/ ketamine for induction
- Midazolam & Diazepam
What reverses benzodiazepines
Flumazenil
Describe opioids can be given for analgesia
- Butorphanol
- Morphine & hydromorphone (not typically used in cattle)
- Buprenorphine (not used in cattle b/c of cost)
What is a side effect of opioids
Excitement or vocalization
List three induction drugs for LA ax
- Ketamine
- Telazol
- Propofol
What is ketamine combined w/ in LA ax
- Benzodiazepin
- GG to make a “double drip”
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
What is ketofol
- Ketamine + propofol IV
- Works well in small ruminants
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
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
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
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
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
When can a small machine be used for the maintenance of ax
- Px < 60 kg
- Using less than 18 mm ETT
What are the oxygen flow rates for maintenance of ax
10 - 22 ml/kg/min
Fill out the following:
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
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
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
Where do we measure indirect BP
- Front leg
- Tail
When monitoring what should MAP be above
60 - 70 mgHg
Where is ECG leads placed
- In tough hide
- Base apex lead
- Can use 16 g needle to place electordes
Describe monitoring ventilation
- Goal: end tidal CO2 btw/ 35 - 45 mmHg
- Ruminants tend to hypoventilate under anesthesia
- Hypocarbia may cause bradycardia in ruminants
What should mechanical IPPV be set to
- Tidal volume: 10 - 20 ml/kg
- RR: 6 - 12 bpm
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
What can cause pneumothorax & emphysema
Excissive airway pressure
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
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
What is the “sweet smell of ruminant anesthesia success”
Eructation
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
