27 – Exotic (Rabbit) Anesthesia Flashcards
(54 cards)
1
Q
Effects of size: difference to dogs and cats
A
- Higher metabolic rate, smaller reserves of glycogen PREDISPOSES to HYPOGLYCEMIA
- *higher oxygen consumption reduced tolerance to HYOXEMIA
- HYPOTHERMIA
2
Q
Hypothermia: effects of size
A
- Higher body surface area to volume ratio
- Radiant heat loss: cover patient!
- Evaporative heat loss
o *Clip as minimal as necessary
o *minimize use of scrub and alcohol solution
3
Q
Respiratory system of a rabbit
A
- Visualization of larynx is difficult
- Prone to laryngospasm
- Obligate nasal breathers
- Thoracic cavity: small, small tidal volume
- Clinical and subclinical respiratory disease
- Be careful with positioning!
o *large abdominal organs push against diaphragm
4
Q
Digestive system of a rabbit
A
- Allow water up to premedication
- Can NOT vomit
- Fast rabbits for 1-2 hours
- Check for food in oral cavity: clean with cotton swabs
- Post operative ileus is common
- Encourage to eat in post-anesthetic period
5
Q
What are the predisposing factors for post operative ileus in rabbits?
A
- Pain
- Starvation
- Stress
- Diet change
- Drugs
6
Q
What do you need to consider for small mammal anesthesia?
A
- Accurate dosing of drugs
o Accurate body weight, dilate drugs if necessary, use appropriate syringe size - Anesthesia protocols
o DO NOT extrapolate from other species - Compression of thoracic cavity
o Hands, instruments, drapes
7
Q
What is the blood volume of rabbits?
A
- 50-78mL/kg
o Less tolerance for hemorrhage
o One cotton tip applicator=0.17ml blood
o 4x4 gauze sponge=7ml blood
8
Q
What are the anesthetic mortalities of rabbits?
A
- Overall risk: 1.39-4.8%
- Sick: 7.37%
- Post anesthetic: 64% mortality occurred
- Peri-anaesthetic GI complications: 38%
9
Q
What increases the anesthetic risk?
A
- Stress (prey)
- Underlying disease
- Failure to address perioperative issues
- Lack of familiarity and expertise
- Increased risk of hypothermia (slows metabolism and delays recovery)
- *prolonged procedures: anesthesia time
10
Q
How can you minimize stress in rabbits?
A
- Provide rabbit friendly environment
- Use premedication to reduce stress during induction
- Minimize handling
- Pain management
11
Q
What are some underlying disease that can increase anesthetic risk?
A
- malnourishment and dehydration
- sub-clinical respiratory disease
- uterine carcinoma
12
Q
Lack of familiarity and expertise that increases anesthetic risk
A
- size
- endotracheal intubation is technically DEMANDING
- fewer veins that are easily accessible for catheterization
- pain
13
Q
What can be done to reduce anesthetic morbidity and mortality?
A
- Supportive care
14
Q
Pre-operative blood tests
A
- Get an idea of PCV, total protein, glucose, BUN
- *glucose as a prognostic indicator for stress and clinical disease
15
Q
How can you avoid disaster?
A
- Be prepared
- Know normal vital parameters
- Full clinical examination and history
- Consider pre-operative blood work
- Stabilize condition before anesthsia
- Don’t starve
- Accurate weight
- *always calculate dose for anesthetic agents, reversals and emergence drugs
16
Q
What are the normal vital parameters of rabbits?
A
- HR: 200-300
- RR: 32-60
- T: 38.5-39.5
17
Q
What are the patient specific complications in rabbits?
A
- Hypoglycemia, ileus
- Possible underlying subclinical disease
- Corneal ulcers
- Increased risk of hypothermia
- Injury (back fracture)
18
Q
What are the 3 roles of premedication?
A
- Reduce stress during handling, induction and pre-oxygenation
- Anesthetic sparing
- Analgesia
19
Q
What are some examples of premedication?
A
- Acepromazine
- Midazolam
- Dexmedetomidine
- Opioids
- Anticholinergic drugs
20
Q
Acepromazine (pre-med)
A
- Long duration
- NOT reversible (prolonged recovery)
- Peak effect after 30-45mins
- Hypotension: peripheral alpha1 receptor blockage (vasodilation)
- *only use in healthy animals
- *don’t usually use in rabbits: long duration and prolongs recovery!
21
Q
Midazolam (pre-med)
A
- WATER soluble, can be administered IM
- *Minimal cardiopulmonary effects
- Produces moderate SEDATION and MUSCLE RELAXATION
- *Reversal: Flumazenil
- *combine with opioid
- *good for rabbits and humans
22
Q
Dexmedetomidine (pre-med)
A
- Mild to profound sedation
- Respiratory and CV depression (not great for older animals)
- Peripheral vasoconstriction
- Reversible: Atipamezole
- *combine with an opioid
- *alternative to midazolam
23
Q
Opioids (pre-med)
A
- Provide analgesia and will increase sedation
- Reversible: Naloxone
- Ex. Buprenorphine: 6-8hrs
- Ex. Butorphanol: 2 hrs
- Ex. Hydromorphone and methadone
24
Q
Anticholinergic drugs (pre-med)
A
- NOT routinely administered as premedication
- Used to treat bradycardia
- Negative effects on GI motility
- Ex. Atropine: 61% possess atropine esterase (ineffective)
- Ex. Glycopyrrolate: slower onset time
25
Induction of anesthesia
- ALWAYS pre-oxygenate
- Always have a person monitoring
- Have monitoring attached to patient
- IV catheter
- Have enough induction agent
- Masking down should NOT be first option in rabbits
- *prefer injectable
26
Why should masking down NOT be first option in rabbits?
- Humane exposure
- Stressful
- Not enough time to intubate
27
Injectable induction agents: examples
- Ketamine
- Propofol
- Alfaxalone
- *titrate to effect to AVOID induction apnea
28
Ketamine (injectable induction)
- Combine with benzodiazepine (midazolam)
- HIGH doses can provide surgical ANESTHESIA
29
Propofol (injectable induction)
- Requires IV access prior to induction
30
Alfaxalone (injectable induction)
- Could be given IM: large volume
31
Induction of anesthesia: VOLATILE AGENTS
- Should only be 2nd choice to IV induction
- Always use with premedication to reduce stress and struggling
- Beware of breath holding
- Apnea induced bradycardia
- Introduce volatile gradually
- Pre-oxygenate if possible
- *Oxygen flow rates greater than 100mg/kg/min with well fitted mask
32
What are examples of volatile agents for induction of anesthesia?
- Isoflurane
- Sevoflurane
33
Isofluarane
- MAC: 2.5%
- Pungent smell: breath holding likely
- Induction apnea
34
Sevoflurane
- MAC: 3.5-4.1%
- Less pungent: better tolerated
- Faster induction?
- Induction apnea
35
Face mask for rabbits
- Close fitting
- Diaphragm can be adapted using an exam glove
- Clear: visual assessment
- Low volume: minimize dead space
- *if condensation=O2 is too low!
36
Anesthesia induction chambers
- Multiple sizes
- Bigger chamber=longer it takes
- If get excitement phase=bounce of walls and can HURT themselves
- *want it as small as possible
37
Lidocaine constant rate infusions
- Prokinetic effects
- Improved food intake and fecal output in rabbits following ovariohysterectomy
- Anesthetic sparing (reduces isoflurane MAC)
- Analgesic
- Anti-inflammatory/anti-endotoxin
38
Intubation of rabbits: options
- Blind
- Direct visualization
o Videoendoscope
o Laryngoscope
o Otoscope
39
Why intubate a rabbit?
- Protects airway
- Allows efficient oxygen supplementation
- Allows positive pressure ventilation
- Reduces human exposure
40
Rabbit intubation ‘steps’
- 2.0-3.5mm (un) cuffed ET tube
- Ensure rabbit is adequately anesthetized
- Pre-oxygenate
- Prone to laryngospasm: use lidocaine
- Sternal recumbency with hyper-extended neck (nose to ceiling)
o Align larynx and trachea with oropharynx
- Continuously monitor HR during induction/intubation
41
Blind method intubation technique
- Difficult initially
- Easy and quick to perform once experienced
- No extra cost
- Possible damage to glottis and risk of laryngospasm
- Possible unsuccessful due to entrapment of epiglottis
- Risk of aspiration if unnoticed presence of food in pharynx
42
Steps for blind method intubation
- Premeasure ETT to level of larynx
- Sternal recumbency and hyper-extended neck
- Interest ET tube to pre-measured point
- Instill lidocaine 2% (neat) via small catheter through ET tube
- Gently advance ET-tube during inspiration while
o Listening to connecter end of tube
o Watching capnograph
43
How do you confirm tracheal intubation?
- Ventilate and listen for respiratory sounds on BOTH SIDES OF THORAX
- Use capnograph
- Coughing
- Watch for condensation
- *repeated attempts of intubation is NOT recommended
o Risk of laryngeal trauma and spasm=respiratory obstruction
44
Laryngoscope/otoscope intubation technique
- Direct visualization possible
- Can move soft palate and expose glottis if necessary
- Technically challenging compared to dog/cat
- Unexperienced may cause damage
- Minimal equipment necessary: laryngoscope/otoscope + stylet
45
Intubation with direct visualization steps
- Sternal recumbency and hyper-extend neck
- Assistant to open mouth
o Hold wide open: use bandage material as a retractor
- Gently pull tongue out of mouth
- Use small laryngoscope
- Insert ET tube
46
Endoscopic method
- Direct visualization allows rapid and accurate intubation
- Technical challenging
- No RISK of aspiration or soft tissue damge
- Expensive equipment needed
- Side-by-side or endoscope can act as stylet
47
What are some complications with rabbit intubation?
- Difficult placement
- Laryngospasm
- Trauma to oropharyngeal soft tissue
- Tube dislodgement, occlusion and kinking
- Postintubation oropharyngeal swelling
48
Supraglottic airway device: V-gel
- Some experience necessary (online training)
- Always use with capnograph
- Can be easily dislodged if animal is moved
- Faster placement than ET intubation
- Less trauma than blind intubation
- Disadvantages: Tongue can get blue or black OR occlude airway (use with capnograph)
49
Rabbit anesthesia: IV access
- Conscious rabbit: apply local anesthetic cream (EMLA)
- Cephalic vein
- Lateral saphenous
- Marginal auricular vein
- *fluids: 10mL/kg/hr (+/- 2.5-5% dextrose)
50
What are some complications with using the marginal auricular vein?
- Sloughing
- Chemical phlebitis
- Mechanical irritation from catheter or bandage
- *do NOT use central auricular artery
51
Monitoring anesthetic depth
- Palpebral reflex, eye positions=unreliable (eye will stay central)
- Nictitans membrane will move over cornea
- *corneal reflex should be maintained
52
Monitoring CV system
- Auscultation
- Doppler
- Pulse oximetry: ear, tongue, digit
- ECG
- Temperature (avoid hypo and hyperthermia)
53
Post operative care
- Analgesia
o NSAIDs: meloxicam
o Opioids: buprenorphine, hydromorphone, butorphanol
- Stress free environment
- *Continue monitoring
- Feed as soon as possible
54
If a prolonged recovery, check for
- Hypothermia
- Hypoglycemia
- Residual drug effects (reversal)
