Swine anesthesia Flashcards

1
Q

Important points to emphasize regarding swine:

Behavior?

Physical exam?

A
  • Behavior–not amiable for restraint, difficult to grab
  • PE difficult to do sometimes
    • Observe before handling
    • If part of herd: questions about its interactions
    • History of porcine stress in herd?
    • Pet
      • Better history
      • Thoracic auscultation–PE can still be difficult
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2
Q

Important oints to emphasize regarding swine

Veins/arteries?

Injection sites?

Intubation?

Alpha2’s?

Stress?

A
  • Veins and arteries not readily accessible
  • Limited sites for injections (fat)
  • Intubation can be very difficult
  • Swine = most resistant species to sedative effects of alpha2’s
  • Stress–> trigger to porcine stress syndrome
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3
Q

Restraint

Easy?

Equipment involved?

Which pigs are easiest?

A
  • Not very amiable to restrain–stress easily
    • Not much to grab
    • Adults can be very strong
    • Can use snare (if needed)
    • Stanchion = good control
    • Baby pigs and small, mini breeds easier
      • May squeal when restrained
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4
Q

Injections

Needle?

Sites?

A
  • IM injections necessitates using needles at least 2-3in long to avoid injections into fat
  • Sites
    • IM injection behind the ear-neck muscle
      • Using ‘butterfly’ avoids restraint (good small pigs)
    • SQ injection in skin fold of rear leg
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5
Q

Venous puncture

6 sites

A
  • Cranial vena cava–site is proximal to manubrium
    • Used for large volumes
  • Cephalic vein proximal–young/small pigs
  • Jugular–deep in jugular groove
  • Medial caudal vein–at the first movable tail joint–ventral midline
  • Subcutaneous abdomen vein
  • Ear vein
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6
Q

IV catheter placement

Difficulty?

Requires what?

Sites?

A
  • Tough skin, veins deep, not readily accessible
  • Almost always requires sedation
    • Difficult to restrain
    • Squealing
    • Must avoid stress
  • Ear veins
    • Auricular vein
    • Small ears more difficult
  • Lateral saphenous
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7
Q

Preparation for anesthesia

Fasting?

A
  • Adults = 12-24hrs
    • Improper fasting–> gas accumulation producing distention; inc. pressure on diaphragm impeding ventilation
    • Inc. risk of vomiting/regurg/aspiration
  • Piglets = held from suckling 3-4hrs, but prone to hypoglycemia
  • Mini pigs = fast up to 12hrs
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8
Q

Sedation

Azaparone

A
  • Butyerophenone (similar to phenothiazines)
  • Only tranquilizer approved for swine in US
  • Used primarily to decrease fighting and anxiety amongst pigs (lower dosages)
  • Sedation at higher dosages
  • IM
  • Boars– >1mg/kg = penile prolapse
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9
Q

Xylazine

A
  • Most resistant species to xylazine and other alpha2’s
    • Does not produce good sedation when used alone
    • May cause vomiting
  • 2-3mg/kg IV may produce rapid but short sedation that is readily abolished as soon as handler approaches/touches pig
  • Add ketamine IM–short-term restraint (20-30min)
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10
Q

Anticholinergics

A
  • Usually not given routinely unless bradycardia warrants
  • Ketamine (usually) and telazol (might) produce salivation–> makes visualizing the larynx difficult and may occlude airway or tube
    • Low doses atropine may minimize secretions (unless suction is available at intubation)
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11
Q

Benzodiazepines

A
  • May produce some sedation when used alone (small/young pigs)
  • Usually combined with other drugs, BUT
    • 0.5mg/kg medazolam IM alone can produce moderate sedation
    • Can also give medazolam intranasal
      • Lab piglets–rapid and reliable sedation
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12
Q

Tiletamine/zolazepam (telazol)

A
  • “Super ketamine/diazepam”
  • Reconstitute powder w/ 5ml sterile water
  • Very reliable sedation and good muscle relaxation
  • Potent–so small volume
  • 4mg/kg IM good for IV catheter placement but not enough for intubation and may produce long recoveries (zolazepam)
  • Tiletamine = responsible for restraint/anesthesia
  • Zolazepam = muscle relaxation and sedation
    • Prolonged recoveries using higher doses
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13
Q

TKX (Telazol, ketamine, xylazine)

Reconstitue with?

Ketamine added–>

Xylazine added–>

T&Z?

Route?

A
  • Reconstitute w/ 250mg ketamine + 250mg xylazine = 5ml total
  • Ketamine adds more restraint, ‘anesthesia’
  • Xylazine provides more sedation, muscle relaxation w/ improved analgesia
  • T&Z diluted down to use smaller dosage of mixture
  • IM
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14
Q

Opioids

Sedation?

Used as? Example?

Post-op pain?

A
  • Not very good for adding sedation to other sedatives for premedication
  • Used as an adjunct to analgesia during anesthesia
    • Fentanyl–bolus or infusion
  • Post-op pain:
    • Fentanyl patches
    • Buprenorphine IV (if poss.) or IM
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15
Q

Induction (if not intubatable w/ premedications)

Mask?

Drugs?

A
  • Mask w/ iso or sevo if close, just not quite intubatable
  • Propofol (amount depends on how sedated w/ premeds)
  • Alfaxalone
  • Thiopental
    • If using ear vein: dilute in syringe to 1:1–avoid irritating vein
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16
Q

Intubation

When?

Why?

Positioning?

Oxygen?

A
  • Should always intubate unless very short procedures (<30-45 min)
  • Protects airway from poss. aspiration
  • Long soft palate–may obstruct airway
  • Allows for ventilation to avoid hypercapnia and minimize chance of hypoxemia
  • Sternal (but some feel dorsal works best)
  • Pre-oxygenate before/during induction (mask or flow) at nose
    • Lidocaine–sprayed on larynx using long urinary catheter–>depress spasms
  • Extend head (do not over-extend)
17
Q

Why are pigs difficult to intubate?

A
  • Difficult to visualize larynx
    • Difficult to open mouth wide
    • Narrow glottis and trachea; long soft palate
    • Thick tongue, fat cheeks
18
Q

Name the labeled structures

A
  • dp = pharyngeal diverticulum
  • ct = long thyroid cartilage on the floor of the larynx
  • pc = pharyngeal recess above larynx
    • Places where the tube can get ‘stuck’
  • e = epiglottis
19
Q

Intubation

Steps

A
  • Carefully extend the stylet through the glottis, into the trachea (a small distance)
  • ‘Thread’ the T tube over the stylet into the trachea WHILE retracting the stylet
  • Must use care to avoid trauma to trachea: hematoma
    • Must turn tube upward once past the glottis
  • Lidocaine airway again, prior to extubation, when pig starts to swallow/chew tube
20
Q

How do you verify proper RT placement?

A
  • ET CO2 wave form
    • Waveform and CO2–only comes from the lungs
      • Only reliable sign
  • Condensation in the tube
  • Breathing moves rebreathing bag
  • “Normal” chest excursion with IPPV
21
Q

Endotracheal tube sizes?

A
  • <10kg = 3-4
  • 10-15 = 4-6
  • 20-40 = 6-8
  • 50-100 = 8-10
  • >100 = up to 16
22
Q

Maintenance and monitoring

Rates?

Head signs?

A
  • O2 flow rate ~50-100ml/kg/min initially, then decrease to 10-30ml/kg/min
  • Iso 2.5-3% then maintenence usually 1.5-2%
  • Head signs not very helpful IMO
    • Want loss of palpebral with deviated eyeball
  • Monitor autonomic signs
23
Q

What is monitored during pig ax?

A
  • ECG–rhythm
  • BP–indirect (doppler and/or oscillometeric)
  • Direct pressure–auricular artery in center of pinna
    • Need to cutdown for other arteries
  • Pulse oximetry
  • Capnography
  • Temperature
24
Q

Maintenance

What is important to remember?

MAP?

Systolic?

A
  • Anesthesia depresses ventilation–and in large/heavy animals hypoventilation is significant
    • Hypoventilation = hypercarbia
    • Hypercarbia will dec. the PaO2
    • Must be ventilated IPPV–to maintain ETCO2 in acceptable range (<50-55mmHg)
  • Keep MAP > 60mmHg
  • Kee systolic > 85mmHg
25
Q

Expected vital parameters: mini and market pigs

Normal life span

Rectal temp

Heart rate

Resp rate

Blood pressure

ETCO2

A
26
Q

What 4 things should be done during recovery?

A
  • Extubate when pig is swallowing/chewing
    • May be prone to spasms once removed
  • If laryngeal edema/spasms suspected: lidocaine w/o dilute phenylephrine drip into larynx (before extubation) is helpful
  • Keep warm (esp. for surgery)–wrap legs
  • Reverse alpha2 agonists if necessary
27
Q

Potential complications (5)?

A
  • Hypoventilation–provide IPPV
  • Hypotension–assess depth
    • Reduce inhalent if poss.
    • Fluids: dobutamine; dopamine
  • Airway obstruction; laryngeal edema
  • Porcine stress syndrome
    • Striated muscle deterioration
    • Malignant hyperthermia
28
Q

What breeds are associated with porcine stress syndrome/malignant hyperthermia?

A
  • Pietran
  • Landrace
  • Large white
  • Poland China
  • Duroc
29
Q

Porcine stress syndrome/MH: pathophysiology

A
  • Inherited–autosomal recessive mutation in the ryanodine gene (Ca release channel)
  • Ca cannot exit sarcoplasmic reticulum
    • Leads to muscle rigidity
    • Hyper-metabolic state–inc. temp
    • Inc. CO2 (prod. exceeds elimination)
    • Can be fatal
30
Q

MH

Triggers?

A
  • Stress (called capture myopathy in wild animals)
  • Halothane; succinycholine ‘classic’ triggers assoc. w/ anesthesia
  • Has occurred w/ all the inhalents
  • Must have the gene
    • Not all pigs will get MH
31
Q

MH

Signs?

A
  • Rapid onset of tachycardia, tachypnea
  • Hyperthermia (>107 F)
  • Myoglobinuria
  • Inc. K, inc. ionized Ca
  • Unstable BP
  • Muscle rigidity
  • Rapid rise in ETCO2 (despite increases in RR/volume)
    • Hypermetabolic state–overproduction of CO2
  • Dysrhythmias lead to cardiac arrest
32
Q

MH

Antidote?

Problem?

A
  • Dantrolene
    • Suppresses Ca release but doesn’t inhibit uptake of Ca by muscle cells
      • Aids in Ca removal from SR
    • Direct relaxing effect on skeletal muscle
  • Problem–most likely won’t have it
    • Call medical center in town to get it fast
33
Q

MH

Treatment?

A
  • Discontinue inhalent anesthesia; change to fresh machine (w/ new equipment)
  • Use propofol or alfaxalone to keep asleep (if necessary) w/ midazolam
  • Institute body cooling–ice baths or alcohol
  • Cool IV fluids
  • Hyperventilate to dec. ETCO2
  • Blood gas–for pH, BE, PaCO2, PaO2
  • Metabolic acidemia can/will occur
    • If PCO2 is still high, Na bicarbonate will only increase CO2
    • Still might be necessary (small amounts) if BE > 10-12 mEq/L
34
Q

Anesthesia for MH susceptible pig?

A
  • Pre-treat w/ dantroline 5mg/kg PO 8-12 hours before surgery
  • May need to repeat pre- and post-operatively
  • Use injectables (propofol and opioids/medazolam) if necessary to avoid inhalants
35
Q

Lumbosacral epidural

Use?

Process?

A
  • Facilitate C-section, repair rectal, uterine, vaginal prolapse, other ‘hind-end’ procedures
  • Lumbosacral anesthesia
  • Retrain–chute, sanction, w/ or w/o sedation
  • Palpable depression midline between and just caudal to iliac wings at L6-S1
  • Needle length 2-4cm
    • Up to 4-10cm > 100kg
  • 20mg (1ml) lidocaine/4.5-7kg
36
Q

What drug is used for castration?

A

Lidocaine 2% w/ equal volume saline (for more volume) injected into center of each testicle