2. Rabbit Anesthesia Flashcards
Why should we NOT compare rabbits to dogs and cats?
higher metabolic rate, smler reserves of glycogen predisposes to hypoglycemia
higher O2 consumption so reduced tolerance to hypoemia
hypothermia: high body surface area to V ratio, radiant heat loss - cover patient, evaporative heat loss (clip as minimal as necessary, minimize use of scrub and alcohol solution
What is unique about the respiratory system of rabbits?
visualization of larynx is difficult
prone to laryngospasm
obligate nasal breathers
thoracic cavity: very small, small tidal volume (4-6ml/kg)
clinical and subclinical resp dz (P. multocida)
be careful with positioning bc lg abdominal organs can push against diaphragm
What is unique about the digestive system of the rabbit
Allow water up to premed
can NOT vomit
fast rabbits 1-2hrs to reduce presence of food in oral cavity
check for food in oral cavity - clean w/ cotton swabs (guinea pigs)
post-op ileus is common, predisposing factors: pain, starvation, stress, diet change, drugs
encourage to eat in post-anes period
What do we need to consider with small mammal anesthesia?
Accurate dosing of drugs: accurate BW, dilute drugs if necessary, use appropriate syringe size (insulin syringe)
Anesthesia protocols: don’t extrapolate from other species
Compression of thoracic cavity: hands, instruments, drapes
What is the average blood volume of a rabbit?
50-78ml/kg
they have less tolerance for hemorrhage
A cotton tip applicator can hold 0.17ml of bleed
A 4x4 gauze sponge can hold 7ml of blood
What is the anesthetic mortality of rabbits?
overall: 1.39-4.8%
sick: 7.37%
Post anesthesia: 64%
Perianasthesia GI: 38%
What increases the anesthetic risk in rabbits?
Stress (prey species): provide a rabbit friendly environment, use premed to reduce stress during induction, minimize handling, pain management
Underlying dz - malnourished (dental tx) and dehydration, sub-clinical resp dz (pasteurellosis), uterine carcinoma
Failure to address perioperative issues
Lack of familiarity and expertise bc of size, ETT technically demanding, fewer veins for catheter, pain
inc risk of hypothermia (slow metabolism and delayed recovery)
Prolonged procedures > anesthesia time > ileus
Supportive care will reduce anesthetic morbidity and mortality
What is your normal pre-op blood tests
- PCV: 34%–43%
- TP: 5.0–7.5 g/dL
- BG: 4.1–8.2 mmol/L
- Blood glucose can be used as a prognostic indicator (stress, clinical disease)
- BUN 15-30 mg/dL
How can we avoid disaster with rabbit anesthesia?
Be prepared, know normals, full clinical exam and hx, consider pre-op blood work
stabilize condition b4 anesthesia, don’t starve, accurate rate
always calculate doses for anesthetic agents, reversals and emergency drugs
What is the normal HR, temp and RR of a rabbit?
Heart Rate 200-300
Respiratory Rate 32-60
Temperature 38.5-39.5
What are some anesthesia and procedure related complications?
hypothermia/tension/ventilation
hypoxemia
Bradycardia
procedure: pain, hemorrhage
What drugs might we use in rabbits for premed?
Acepromazine, midazolam, dexmedetomidine, opioids, anticholinergic drugs
How is acepromazine used for rabbit anesthesia?
- 0.1-0.25 mg/kg (IM, SC, IV)
- Long duration, not reversible – prolonged recovery
- Peak effect after 30-45 min
- Hypotension: peripheral α1 receptor blockade – vasodilation
- Only use in healthy animals
Very long lasting (6-8hrs), not reversable
How is midazolam used in rabbit premed
- 0.5 - 2mg/kg (IM, SC, IV)
- Water soluble can be administered IM
- Minimal cardiopulmonary effects
- Produces moderate sedation and muscle relaxation
- Reversal: Flumazenil (0.05-0.1mg/kg IV, IM)
- Combine with an opioid
How is dexmedetomidine used in rabbit premed?
- 0.02-0.05mg/kg (IM, SC)
- Mild to profound sedation
- Respiratory and cardiovascular depression
- Peripheral vasoconstriction
- Reversible with Atipamezole
- Combine with an opioid
How is opioids used in rabbit premed?
- Provide analgesia and will increase sedation
- Reversible with Naloxone (0.01-0.1mg/kg, IM, IV)
Buprenorphine - 0.05 - 0.1mg/kg (IM, SC, IV), 6-8 hours
Butorphanol - 0.5 - 2 mg/kg (IM, SC, IV) 2 hours
Hydromorphone - 0.1- 0.3mg/kg (IM, SC, IV)
Methadone - 0.3-0.7 mg/kg (IM, SC, IV)
How are anticholinergic drugs used in rabbit premed?
- Not routinely administered as premedication
- Used to treat bradycardia
- Negative effects on gastrointestinal motility!
Atropine - 0.1-0.2 mg/kg (IM, SC, IV)
- 61% of rabbits possess atropine esterase
Glycopyrrolate - 0.01-0.1mg/kg (IM, SC, IV)
What do we need to do when inducing rabbits?
always preoxygenate
always monitor during induction/intubation
have monitoring attached to patient
IV cath, have enough induction agent
masking down should not be first option for rabbits - humane exposure, stressful, not enough time to intubate
What are the injectable induction agents for rabbits?
KETAMINE (1- 5 mg/kg, IV, IM)
* Combine with benzodiazepine (midazolam 0.5mg/kg)
* High doses (up to 25mg/kg) can provide surgical anesthesia
PROPOFOL (2-8 mg/kg, IV)
* Requires IV access prior to induction
ALFAXALONE (1-4 mg/kg IV)
* Could be given IM – large volume
TITRATE TO EFFECT TO AVOID INDUCTION APNEA
KETAMINE (1- 5 mg/kg, IV, IM)
* Combine with benzodiazepine (midazolam 0.5mg/kg)
* High doses (up to 25mg/kg) can provide surgical anesthesia
PROPOFOL (2-8 mg/kg, IV)
* Requires IV access prior to induction
ALFAXALONE (1-4 mg/kg IV)
* Could be given IM – large volume
What do we need to keep aware of when using volatile induction agents?
should only be 2nd choice to IV induction
always use w/ premed to reduce stress and struggling
beware of breath holding
apnea induced bradycardia
introduce volatile gradually
pre-oxygenate if possible
oxygen flow rates greater than 100ml/kg/min with well fitted mask
What volatile agents are used for induction?
ISOFLURANE
* MAC: 2.5%
* Pungent smell – breath holding more likely
* Induction apnea
SEVOFLURANE
* MAC 3.5-4.1%
* Less pungent – better tolerated
* Faster induction ? - Depth of anesthesia may alter more rapidly
* Induction apnea
What is a facemask?
Mask for volatile agents
close fitting: reduces envirocontam, avoid inhaling of room air
Diaphragm can be adapted using an exam glove
clear: visual assessment
low V: minimize dead space
What is lidocaine constant rate infusions?
prokinetic effects
improved food intake and fecal output in rabbits following OHE
anesthetic sparing (reduces iso MAC)
analgesia
anti-inflam/anti-endotoxin
How do we intubate a rabbit?
can use a mask, or v-gel (supraglottic airway device)
or blind intubation, can do direct visualization (videoendoscope, laryngoscope, otoscope
