Exotic Anesthesia Flashcards
How is exotic anesthesia different than in dogs & cats?
- higher metabolic rate & smaller reserves of glycogen predisposes to HYPOGLYCEMIA
- HIGHER OXYGEN CONSUMPTION, reduced tolerance to HYPOXEMIA
- HYPOTHERMIA: high body surface area to volume ratio; radiant heat loss (cover patient); evaporative heat loss (clip as minimally as possible; minimize use of scrub & alcohol solution)
What is important about the respiratory system of a rabbit?
- visualization of larynx difficult
- prone to laryngospasm
- obligate nasal breathers
- thoracic cavity v sm, sm tidal volume (4-6 mL/kg)
- clinical & subclinical respiratory disease (P. multocida)
- be careful w/ positioning (large abdominal organs push against diaphragm)
What is important about the digestive system of a rabbit?
- allow water up to premedication
- CANNOT vomit
- fast rabbits for 1-2 hrs to reduce presence of food in oral cavity
- check for food in oral cavity (clean w/ cotton swabs in guinea pigs)
- post operative ileus is common (predisposing factors: pain, starvation, stress, diet change, drugs)
- encourage to eat in post-anesthetic period
What should you consider during small animal anesthesia?
- Accurate dosing of drugs (accurate body weight, dilute drugs if necessary, use appropriate syringe size (insulin syringe))
- anesthesia protocols (dont extrapolate from other spp)
- beware of compression of thoracic cavity (hands, instruments, drapes)
What is important regarding blood volume in rabbits?
less tolerance for hemorrhage
What increases the anesthetic risk in rabbits?
- stress
- underlying disease
- failure to address perioperative issues
- lack of familiarity
- increased risk of hypothermia (slow metabolism, delayed recovery)
- prolonged procedures (anesthesia time -> ileus)
SUPPORTIVE CARE WILL REDUCE ANESTHETIC MORBIDITY & MORTALITY
How to reduce stress in prey spp?
- provide rabbit friendly enviro
- use premedication to reduce stress during induction
- minimize handling
- pain managment
What are potential underlying diseases in rabbits the increase anesthetic risk?
- malnourishment (dental treatment) & dehydration
- sub-clinical respiratory disease (Pasteurellosis)
- uterine carcinoma
What are examples of lack of familiarity and expertise that increase anesthetic risk in rabbits?
- size
- endotracheal intubation is technically demanding
- fewer veins that are easily accessible for catheterization
- pain
what pre-operative blood tests should you do in rabbits?
- PCV, TP, BG (can be used as a prognostic indicator for stress & clinical disease), BUN
What is normal heart rate in a rabbit?
200-300
What is normal respiratory rate in a rabbit?
32-60
What is normal temperature in a rabbit?
38.5-39.5 C
How do you avoid disaster during anesthesia in rabbits?
- be prepared
- know normal vital parameters
- full clinical exam & hx
- consider preoperative blood work
- stabilize condition before anesthesia
- dont starve
- accurate weight
- ALWAYS CALCULATE DOSES FOR ANESTHETIC AGENTS, REVERSALS, & EMERGENCY DRUGS!
Why should you use premedication in exotics?
- reduces stress during handling, induction, pre-oxygenation
- anesthetic sparing
- analgesia
Acepromazine in rabbits?
- IM, SC, IV
- long duration, not reversible (prolonged recovery)
- peak effect after 30-45 min
- hypotension: peripheral A1 receptor blockade (vasodilation)
- only use in healthy animals
- DONT necessarily use this in sm mammals
Midazolam in rabbits?
- IM, SC, IV
- water soluble so can be administered IM
- minimal cardiopulmonary effects
- produces moderate sedation & muscle relaxation
- reversal: flumazenil
- combine w/ opioid
Dexmedetomidine in rabbits?
- IM, SC
- mild to profound sedation
- respiratory & cardiovascular depression
- peripheral vasoconstriction
- reversible w/ atipamezole
- combine w/ an opioid
Opioids in rabbits?
- provide analgesia & will increase sedation
- reversible w/ Naloxone
- Buprenorphine (6-8 hrs IM, SC, IV); Butorphanol (2 hrs IM, SC, IV); Hydromorphone (IM, SC, IV); Methadone (IM, SC, IV)
What is important about anti-cholinergic drugs in rabbits?
- not routinely administered as premed
- used to treat bradycardia
- negative effects on GI motility!
- Atropine: IM, SC, IV; 61% of rabbits possess atropine esterase
- Glycopyrrolate: IM, SC, IV
How do you induce anesthesia in rabbits?
- always preoxygenate
- always have a person monitor the patient during induction/intubation
- have monitoring equipment attached to the patient
- IV catheter
- have enough induction agent
- masking down should not be the first option in rabbits
Which injectable agents do we use to induce anesthesia in rabbits?
- Ketamine (IV, IM): combine w/ benzodiazepine (midazolam); high doses can provide surgical anesthesia
- Propofol (IV): requires IV access prior to induction
- Alfaxalone (IV): could be given IM - large volume
TITRATE TO EFFECT TO AVOID INDUCTION APNEA
How to induce anesthesia in rabbits with volatile agents?
- should only be 2nd choice to IV induction
- always use w/ premed to reduce stress & struggling (back fracture)
- beware of breath holding
- apnea induced bradycardia
- introduce volatile gradually
- introduce volatile gradually
- pre-oxygenate if possible
Iso in rabbits?
- MAC: 2.5%
- pungent smell - breath holding more likely
- induction apnea
Sevo in rabbits?
- MAC 3.5-4.1%
- less pungent (better tolerated)
- faster induction? (depth of anesthesia may alter more rapidly)
- induction apnea
Facemask in rabbits?
- close-fitting
- diaphragm can be adapted using an exam glove
- clear: visual assessment
- low volume: minimize dead space
Lidocaine CRI in rabbits?
- prokinetic effects
- improves food intake & fecal output in rabbits following ovariohysterectomy
- anesthetic sparing (reduces isoflurane MAC)
- analgesic
- anti-inflammatory/anti-endotoxin
How do we maintain rabbit airways during anesthesia?
- mask
- V-gel (supraglottic airway device)
- intubation
Why should we intubate rabbits?
- protects airway
- allows efficient oxygen supplementation
- allows positive pressure ventilation
- reduces human exposure
what is important regarding intubation of a rabbit?
- ensure rabbit is adequately anesthetized
- pre-oxygenate
- prone to laryngospasm: use lidocaine (careful toxic dose)
- sternal recumbency w/ hyper-extended neck (to align larynx & trachea w/ oropharynx)
- continuously monitor heart rate during induction/intubation
What is important about blind intubation in a rabbit?
- technically difficult initially
- easy & quick to perform once experienced
- no extra cost
- possible damage to glottis & risk of laryngospasm
- possible to be unsuccessful due to entrapment of epiglottis
- risk of aspiration if unnoticed presence of food in the pharynx
how do you blind intubate a rabbit?
- premeasure ETT/atomizer to level of larynx
- sternal recumbency & hyper-extend neck
- insert ET tube to pre-measured point
- instill lidocaine 2% neat via small catheter/atomizer through ET tube
- gently advance ET-tube during inspiration while listening at the connector end of the tube & watching the capnograph
How do we confirm tracheal intubation in rabbits?
- ventilate & listen for respiratory sounds on both sides of thorax
- use capnograph
- coughing
- watch for condensation (fogging of the tube during expiration)
REPEATED ATTEMPTS OF INTUBATION ARE NOT RECOMMENDED. RISK OF LARYNGEAL TRAUMA & SPASM -> RESPIRATORY OBSTRUCTION
What is important about intubation of a rabbit with a laryngoscope/otoscope?
- direct visualization possible
- can move soft palate & expose the glottis if necessary
- technically challenging compared to dog & cat
- unexperienced user can cause tissue damage
- minimal equipment necessary: laryngoscope/otoscope + stylet
How do you intubate a rabbit w/ direct visualization?
- sternal recumbency & hyper-extended neck
- requires an assistant to open the mouth
- hold rabbit’s mouth wide open
- gently pull tongue out of mouth
- use small laryngoscope
- insert ET tube
How do you intubate a rabbit with the endoscopic method?
- direct visualization allows rapid & accurate intubation
- technically challenging (learning curve)
- no risk of aspiration or soft tissue damage
- expensive equipment needed
- side-by-side or endoscope can act as stylet
What are potential complications of rabbit intubation?
- difficult placement
- laryngospasm
- trauma to the oropharyngeal soft tissue
- tube dislodgement, occlusion, & kinking
- postintubation oropharyngeal swelling
What is a supraglottic airway device (V-gel) for rabbits?
- some experience necessary (online training)
- always use w/ capnograph!
- can be easily dislodged when animal is moved
- faster placement than ET-intubation
- less trauma than blind intubation
How do you get IV access in a rabbit for anesthesia?
- in a conscious rabbit, apply local anesthetic cream (EMLA)
- cephalic vein, lateral saphenous, marginal auricular vein
How do you monitor anesthetic depth in a rabbit?
- palpebral reflex, eye position: unreliable
- nictitans mb will move over cornea
- corneal reflex should be maintained
How do you monitor the cardiovascular system in a rabbit?
- auscultation
- doppler
- pulse oximetry: ear, tongue, digit
- ECG
- temperature (avoid hypo & hyperthermia)
What kind of post operative care is important after rabbit anesthesia?
- analgesia: NSAIDs (Meloxicam SC); opioids (buprenorphine, hydromorphone, butorphanol)
- stress free environment
- continue monitoring!
- prolonged recovery -> check for hypothermia, hypoglycemia, residual drug effects (reversal)
- feed ASAP
