what are routes of admin of anesthesia
IM
IV
inhalational
when are IM inductions used and what is used
ex. feral cat
ketamine based
when are inhalation induction agents used
some exotics, small mammals
cats, dogs, foals occasionally
what are factors affecting the route of administration
- access to vein
- temperament of animal
- speed of induction required
what factors influence induction
- speed of injection (too fast, too slow, premedication alters)
- hypalbuminemia
how do alpha 2 agonists affect the induction speed
there might be a slower response to the induction agent
how does hypoalbuminemia affect induction
less albumin in the blood for the drug to bind to –> propofol is highly protein bound –> less albumin there might need a lower dose than expected
what are medications used for co-induction
midazolam (beware excitation)
fentanyl
ketamine
what are the purposes of co-indcution agents (2)
- minimize doses
- minimize CVS effects
how is anesthesia maintained
inhalation agents most common
injection (IV)
why are IV anesthetics not prefered for maintanence
can be expensive and they depress ventilation
what can be used to supplement anesthesia and add analgesia
- fentanyl
- ketamine
- lidocaine
what are the options for airway management (3)
- mask
- supraglottic airway
- endotracheal intubation
what are the disadvantages of using mask induction
- risk of leak of gases
- difficult to hold in place
- doesn’t protect against aspiration
when is mask induction helpful
very small patients
what are laryngeal masks
intermediate between mask and ETT
sits over larynx, doesn’t enter trachea
how can ET tubes be inserted
orally
nasally
what are the benefits of ETT
- allows patent airway (relaxation of tissues)
- allows anesthesia to support ventilation
- protect against aspiration of material (regurgitation, hemorrhage, saliva)
what are the methods of ET intubation
blind
manually assisted
laryngoscope guided
bronchoscope guided
what are cats prone to when intubating with an ET and how do you prevent it
laryngospasm
lidocaine spray
how are horses intubated
how do you tell if the tube is in the trachea (5)
- visual conformation
- condesation in trasparent tubes
- breathing system bag movement
- palpation of tube
- capnography
what are the steps following intubation
- secure tube
- inflate the cuff (just enough to stop leak)
should you always intubate a dog?
easy to intubate ususally
airway may be affected by the anatomy
regurgitation more likely in some dogs
should you always intubate a horse?
maintain airway well
evidence in cats may increase anesthetic risk
so for short procedures/healthy animals not necessary to intubate
should you always intubate a pig/rabbit?
should you always intubate ruminants?
high regurgitation risk
intubation very important if GA
how long should the ETT be
not past point of the shoulder (can enter 1 bronchus)
what are the risks of ETT intubation (8)
- laryngospasm
- trauma/swelling (post op)
- endobronchial intubation
- kinking ETT
- obstruction with secretions (clots of blood)
- obstruction of bevelled end
- tracheal stenosis (rare)
- tracheal rupture (rare)
what are 2 good practices before induction
- place IV line
- pre oxygenate (if not stressful)
how would you induce and maintain anesthesia in a 2 yo healthy lab for an ovariohysterectomy
acepromazine + methadone IM pre med
IV propofol induction
isoflurane maintenance
how would you maintain anesthesia in a 7 yo GSD with a ruptured splenic mass
poor pulse, pale
methadone pre med
propofol induction in combo with medazolam so we have to use less propofol
how would you induce a bulldog for airway surgery
low dose alpha2 + methadone pre med
concerned about aspiration, and want quick recovery
definetly pre-oxygenation
induction: rapid in sternal recumbency until tube cuffed, if regurgitates, head down (drain) and have suction ready
what is IPPV
intermittent positive pressure ventilation
why is IPPV needed for anesthesia
anesthesia depresses ventilation
or pathophysiology may require ventilation (diaphragmatic rupture)