Maintenance of anaesthesia Flashcards
(34 cards)
Do we always have to intubate?
always recommend ET intubation regardless of method of induction or maintenance
aka yes
When can you intubate?
sufficient depth of anaesthesia
eyes rotated ventrally
minimal sluggish palpebral reflex
loose jaw tone
no swallowing reflex on stimulation
Why should we always intubate?
deliver oxygen
deliver inhalational anaesthetic if required
protect airway from occlusion or aspiration
allow ventilation to be supported if depressed
What is important to note about intubation in cats?
spray larynx with local anaesthetic to desensitize and reduce laryngospasm during intubation (lidocane spray)
What are problems we can run in with ET tubes?
if no eye, end could be blocked
sometimes it goes in one main bronchi
could get squeezed
overinflation damages trachea
Why do we have to maintain anaesthesia?
duration of action of IV induction agents is generally 5-10 min after which spontaneous recovery of consciousness will occur
needed to prolong unconsciousness for the required duration
What are the 3 ways o maintain anaesthesia?
intravenous (TIVA)
inhalational
combo of both (PIVA)
What are the advantages of TIVA?
lower cost of equipment
environmentally friendly
less CV side effects
What are the disadvantages of TIVA?
higher cost of drugs
increased incidence of awareness
technically more demanding
rely in metabolism to recover
rely on IV access
What are the advantages of inhalational maintenance?
lower cost of drugs
rely on exhalation to recover
low level of metabolism
What are the disadvantages of inhalational maintenance?
higher cost of equipment
not environmentally friendly
What are the effects of GA agents on the systems?
CVS depression: drop in CO, vasodilation, reduced BP when monitoring
resp depression: decreased resp rate, tidal volume, minute volume)
CNS depression: unconsciousness
What are the injectable agents for maintenance?
propofol
alfaxalone
ketamine (used at low analgesic doses)
What other agents will be used with injectable agents for maintenance?
benzodiazepines
lidocaine
opioids
inhavalants (PIVA)
Is TIVA intermittent or continuous?
intermittent: concentration goes up and down a lot VS every time you top up
continuously stressing out the CVS
What are the pharmacokinetic properties of inhalational agents for maintenance?
administered + removed from body by lungs
metabolised in low percentage by liver
How are inhalational agents for maintenance absorbed and used by the body?
from alveoli agent is absorbed into blood -> brain
redistributed into other tissues including fat
What is MAC?
minimum alveolar concentration
what is required to prevent movement in response to painful stimulus in 50% of the animals
How much inhalational agent do i need?
aka what potency is needed to maintain anaesthesia
for clinical anaesthesia aim for slightly over MAC
varies between species, depends on other sedative/anaesthetic agents
What does not affect MAC?
length of anaesthesia
gender
blood pH
What factors can affect MAC?
hypothermia (decrease)
hyperthermia (increase)
very young (increase)
old (decrease)
severe hypoxia/hypercapnia (decrease)
severe anaemia (decrease)
severe hypotension (decrease)
CNS depressant drugs (decrease)
excitation (increase)
pregnancy (decrease)
Which inhalant agent causes the most reduced cardiac output?
halothane
some with iso/sevo
Which inhalant agent has a better maintenance of respiration?
sevoflurane
Which inhalant agent is most metabolised?
halothane
