Swine Anesthesia Flashcards
How are anesthetic agents used in swine?
off label
(extra-label use of drugs permitted when animal health is threatened, per FARAD)
How are large pigs typically handled?
don’t typically tolerate physical restraint (LOUD) - chute, sling, boards
- forking may make them lay down and relax
What 5 conditions are pigs susceptible to under anesthesia? How are their respiratory systems especially affected?
- ventricular arrhythmias
- vasospams - challenging to intubate, put lidocaine on larynx
- decreased FRC
- increased V/Q mismatch
- hypoventilation, hypoxemia
What should the ventilator pressure be set at for pigs? Why?
no more than 22 cm H2O pressure
lungs are especially susceptible to damage
How are pigs fasted prior to an anesthetic event?
- 6-12 hour fast
- free access to water until sedation
What is the most common mode of administration of premeds and sedation in pigs? What are the 4 most common combinations?
IM —> pigs do not tolerate the handling necessary for IV
- Ketamine + Xylazine + Midazolam
- Ketamine + Xylazine + Butorphanol
- Ketamine + Midazolam
- Ketamine + Acepromazine
What alpha-agonist is most commonly used for premedication in pigs? What kind of dose do they tolerate? What side effect is seen?
Xylazine - not typically effective sedation if used alone
higher doses compared to other farm animals
vomiting
What is the most common opioid used in premedication in pigs? How do pigs typically respond? Which ones are avoided?
Butorphanol - less sensitive to opioids
Morphine, Fentanyl, Hydromorphone - causes excitement and respiratory depression
What family of drugs provide the most reliable sedation in pigs?
benzodiazepines (Midazolam)
- no distribution
What access is used for induction in pigs? What drugs are most commonly used?
ear veins
- propofol*
- ketamine*
- alfaxalone
How can smaller pet pigs be induced when there is poor venous access? What are the 2 main categories of maintenance?
inhalant induction
- inhalants
- CRIs of ketamine, lidocaine, midazolam, alpha-2 agonists, fentanyl, or combinations
What 3 things make intubating pigs difficult? What is required to make it easier?
- pigs are nasal breathers
- soft palate is anterior to the epiglottis
- pigs have a blind pouch in the pharynx - pharyngeal diverticulum
angling of the ETT
How are pigs intubated?
- ensure the patient is at the adequate depth and place in dorsal or sternal recumbency
- apply 2% lidocaine to the arytenoids
- use ETT size up to 16 mm and special long laryngoscope blades
- use ETCO2 to confirm placement
smaller pigs are more challenging
What causes malignant hyperthermia? What breeds of pigs are susceptible? Less susceptible?
stress/anesthesia causes Ca to be released into the sarcoplasmic reticulum and a mutation of ryanodine receptors impedes homeostasis = generalized skeletal muscle contraction
Pietrain, Poland China, Landrace
Large White, Yorkshire, Hampshire
What are the most common clinical signs associated with malignant hyperthermia?
- hyperthermia
- muscle rigidity
- tachypnea, rising ETCO2
- arrhythmias, tachycardia
- metabolic acidosis
- myoglobinuria, renal failure
- death
What are the 3 main triggers of malignant hyperthermia?
- stress
- halogenated anesthetics - Iso, Sevo
- depolarizing neuromuscular blocking drugs - succinylcholine
What are the main 2 purposes of using neuromuscular blocking agents? What is important to note about their action?
- ophthalmologic procedures, like phacoemulsification of cataracts that require complete stillness of the eyes
- orthopedic procedures
paralyze the patient, but do no provide anesthesia or analgesia
What is the main depolarizing neuromuscular blocking agent used in veterinary medicine? How does it work?
succinylcholine
binds to postsynaptic cholinergic receptors on the motor endplate and causes rapid depolarization, fasciculation, and flaccid paralysis within 1 min, lasting 7-15 mins
What are the 2 classes of non-depolarizing neuromuscular blocking agents? How do they work?
- steroidal - Rocuronium, Vecuronium, Pancuronium
- benzylisoquinoline - Mivacurium, Atracurium, Cisatracurium
competitive ACh antagonists that bind directly to nicotinic receptors on postsynaptic membrane, blocking ACh binding and depolarization of the endplate = muscular paralysis
What monitoring is recommended when using neuromuscular blocking agents?
train-of-four stimulation where consecutive 2Hz stimuli are applied to nerve innervating a muscle group and TOF ratio indicates recovery of blockade
What reversal is used for neuromuscular blocking agents? Why must it carefully be used? What can be added to increase safety?
neostigmine (anticholinesterase)
indiscriminate —> can have cardiac effects that lead to profound untreatable bradycardia
pretreatment with glycopyrrolate (anticholinergic)
What monitoring is most commonly used in swine patients? Where is an arterial line commonly placed?
ECG, SpO2, BP, ETCO2 —> hypoventilation, hypoxemia, hypotension, hypothermia, bradycardia, tachyarrhythmias
auricular artery (IBP)
What depth signs are the best indicators for swine anesthetic depth?
- jaw tone* - chewing = too light
- palpebral reflexes
Why must pigs be carefully ventilated?
peak inspiratory pressure must remain low due to fragility of lungs
- helps treat decreased FRC, atelectasis, and increased V/Q mismatch
What 4 forms of analgesia are recommended in pigs?
- epidurals, local/line blocks
- IM, SQ, or transdermal Buprenorphine
- Fentanyl CRI or patch
- NSAIDs - Ketoprofen, Phenylbutazone, Flunixin, Carprofen**
What must be monitored in pigs recovering from anesthesia? What commonly causes slow recovery?
- ventilation
- pig remaining sternal with head up until extubation
hypothermia
How can smaller and larger pigs be carefully recovered?
swaddle in a towel/blanket until able to stand
assist to stand as needed
(padding!)
What are the 3 most easily observed signs of malignant hyperthermia?
- hyperthermia
- hypercarbia
- muscular rigidity
(can pretreat with Dantrolene, but $$$)
