general anaesthetics Flashcards
whats analgesia
a lack of pain sensation
whats anaesthesia
lack of sensation, total loss of motoric activity
- local
- general
whats local anaesthesia
without loss of conscious
whats general anaesthesia
total loss of consciousness
how many stages are there to general anaesthesia
- stage 1
- stage2
- stage 3
- stage 4
describe stage 1 of general anaesthesia
disordered consciousness - induction
describe stage 2 of general anaesthesia
excitment
what happens in stage 3 of general anaesthesia
surgical anaesthesia - unconsciousness, amnesia, immobility, unresponsive to surgical stimulation
what happens in stage 4 of general anaesthesia
overdose
what types of anaesthetics do we use for induction
injectable anaesthetics
what types of anaesthetics do we use for maintenance
inhalational anaesthetics
injectable anaesthetics
- barbiturates
- propofol
- imidazole anaesthetics
- steroid anaesthetics
- NMDAr antagonists
inhalational anaesthetics
- halothane
- isoflurane
- sevoflurane
- dinitrogen monoxide
- desflurane
- methoxyflurane
barbiturates for use as injectable anaesthetics
- pentobarbital
- methohexital
- hexobarbital
- thiopental
- thiamylal
- venobarbital
steroid anaesthetics for use as injectable anaesthetics
-alfadolone and alfaxolone in combo
imidazoles for use as injectable anaesthetics
- etomidate
- medomidate
dissociative injectable anaesthetics
- ketamine
- tiletamine
properties of an ideal injectable anaesthetic
- water and lipid soluble
- sufficiently potent
- good analgesic activity
- muscle relaxation
- non irritant to tissue
- rapid and safe induction and recovery
- limited effect on vital fnctions
- high TI
- not have direct reno and hepatotoxicity
- rapid metabolism
- no chemical or pharmacological incompatability
- pharmacological antagonist
barbiturates mechanism of action
- GABA bariturate receptor complex allosteric activator
- decr in Ca accumulation -> inhibit release of NTs, stabilisation of membranes
barbiturates pharmacological effects
CNS, circulation, resp - slight overdosing can lead to resp and cardio inhibition
barbiturates duration of action for anaesthesia
short or ultra short acting
barbiturates application
only IV, effective and harmless
short acting barbiturates duration
15-60 mins
ultra short acting barbiturates duration
5-8mins
short and ultra short acting barbiturates distribution
- fast - complete, blood brain barrier
- placenta -> fetus -> pronounced side effect
- redistribution
- accumulation -> no readministration
ultra short acting barbiturates indication
- induction, general anaesthesia, no analgesia
- convulsive state, epilepsy
- euthanasia
ultra short acting barbiturates contra indications
- younger age, under 2 months
- diminished cardiac output
ultra short acting barbiturates therapeutic index
small
ultra short acting barbiturates side effects
- resp depression - neonates
- cardio depression
- tissue irritation
- pre/postnarcotic excitations
which breed of dog are oversensitive to barbiturates
greyhounds - no fatty tissue, 2nd distribution not possible, try to completely avoid use in greyhounds
ultra short acting barbiturates
- thiopental
- metohexital
- hexobarbital
- pentobarbital
- thiamylal
propofol pharmacological effects
- unconscioussness
- muscle relaxation good
- analgesia not pronounced - combo with opioids
propofol duration
IV 30-45mins
propofol distribution
fast - complete, blood brain barrier, placenta
propofol metabolism
quick hepatic and extrahepatic metabolism - in liver failure administration is safe
propofol elimination
in urine in the form of metabolites, mainly as gluronide conjugate or other inactive forms
propofol indications
- induction and maintainance general anaesthesia
- TIVA with opioids
- convulsions, epileptic seizure
propofol contraindications
cardiac, respiratory, renal, hepatic impairment
propofol side effects
- transcient apnoea during induction
- cardiovascular depression
- vomiting, excitation during recovery
- allergy septicaemias
- increased ICP and ocular pressure
propofol proprietary products
- narcofol inj
- vetofol inj
- frescofol inj
- diprivan inj
etomidate anaesthetics receptor
GABAa
etomidate pharmacological effect
- unconsciousness
- muscle relaxation good
- analgesia not pronounced - combo
etomidate duration
up to 10-20mins
etomidate distribution
fast - complete, blood brain barrier, placenta
whats wake up like under etomidate
quick wake up and excitation
etomidate indication
- induction before inhalational anaesthesia
- combo - opioids, short procedure
etomidate side effects
- severe tissue irritation - only IV
- resp depression
- cardiovascular depression none
- adrenocortical suppression - 2-3hr - no cont inf
- pre/post narcotic excitation - frequent and violent
etomidate therapeutic index
broad
metomidate most commonly used species
pigs
metomidate is an anaglogue of what
etomidate
metomidate analgesic effect
moderate, better in combo with azaperone
is metomidate acidic or basic
highly acidic, can only be injected into large veins
are excitations common with metomidate
frequent, pre and post anaesthetic
whats cardio depression like with metomidate
moderate
possible side effects metomidate in horses
tremors, convulsions
steroid anaesthetics fixed combo
alphaxalone+alfadolone = althesin, when used in fixed combo they have a common name
althesin pharmacological effect
- unconscioussness
- muscle relaxation good
- analgesia not pronounced - combo with opioid
althesin onset
IV 30mins, IM 5-10mins
althesin duration
up to 10-30mins
althesin metabolism
quick metabolism, no accumulation -> readministration
althesin recovery
quick
althesin therapeutic index
broad
althesin side effects
- cardio depression - hypotension, neg ionotropic
- histamine release - allergy
- postnarcotic excitation - stimulation during recovery
althesin licensed products
- cremofor - cat, shock in dogs bc of intensive histamine release
- cyclodextrine - dog and cat
ketamine proprietary products
- bioketan inj
- CP-ketamin inj
- narketan inj
- calypsol inj
tiletamine proprietary products
zoletil inj
ketamine indications
-anaesthesia in combo, inductions and maintainance
ketamine contraindications
sole use in horses and dogs, hepatic and or liver impairment, late pregnancy
ketamine side effects
- catalepsy like condition
- increased sympathetic nervous system tone
- increased cardiac output, heart rate, blood pressure, arrythmias
- mild resp depression, tidal volume slightly incr
- salivation
- pre/postanaesthetic excitations, convulsions
- incr ICP/eye pressure
- hallucinations -> missuse, dependancy
in which species can ketamine only be used in combo
horses and dogs
eg opioids, alpha2-agonists, benzodiazepines etc
zoletil how does it come prepared
freshly dissolved in water, saline or 5% dextrose - 14 days if stored in a refrigerator
zoletil onset
very fast onset of unconsciousness, 2-5min
zoletil side effects
- incr sympathetic tone -> tachycardia, arrythmias, hyperthermia, incr ICP
- dose dependant resp depression
- pain response when drug given by IM or SC
types of combined anaesthesia
- balanced anaesthesia
- total intravenous anaesthesia
- neuroleptanalgesia
- ataranalgesia
whats balanced anaesthesia
combo of antimuscarinics, sedatives, opioids, anaesthetics and muscle relaxants
balanced anaesthesia effects
- safe and deep anaesthesia
- pain control
- less side effects
- relaxed body
- smooth recovery
whats TIVA, total intravenous anaesthesia
combo of agents given exclusively by the intravenous route without the use of inhalation agents
whats neuroleptanalgesia
tranquiliser and opioids, a state of sedation combined with analgesia
whats ataranalgesia
benzodiazepine or opioid and ketamine -> zoletile A.U.V
advantages of neuroleptanagesia
- less amount of sedative, safer
- prior anaesthesia - induction safer, analgesia more pronounced
examples of combos used for neuroleptanalgesia
- etorphine, acepromazine
- butorphanol, acepromazine
- fentanyl, fluanisone
- fentanyl, droperidol
physiological signs of neuroleptanalgesia in dogs
- pupil myosis
- circulation - mild bradycardia and hypotension
- musculature - usuay relaxation
- respiration - depression
physiological signs of neuroleptanalgesia in horses
- pupil - mydriasis
- circulation - prolonged tachycardia, hypotension, transcient hypertension + incr hematocrit
- muscles - incr muscle tone, forelimbs ext, hindlimbs flex
- resp - depression
groups of inhalational anaesthetics
organic and inorganic
organic types of inhalational anaesthetics
non halogenated and halogenated
halogenated inhalational anaesthetics
- chloroform
- halothane
- isoflurane
- desflurane
- sevoflurane
- methyoxyflurane
non halogenated inhalational anaesthetics
diethyl ether
criteria for efficacy of inhalational anaesthetics
- good vaporisation
- good blood gas distribution
- lipid solubility, good oil; gas distribution
whats the MAC
minimum alveolar conc
halothane side effects
- teratogenic, carcinogenic, hepatotxic, arrhythmogenic,
- sensitivity to catecholamines incr
- ADH level incr
- EU bans therapeutic use
isoflurane, svoflurane indications
induction and maintainance of general anaesthesia
isoflurane, sevoflurane contra-indications
younger age, pregnant, lactating animals, susceptibility to malignant hyperthermia
isoflurane, sevoflurane side effects
- cardio and resp depression
- cardiac arrhytmias
- malignant hyperthermia
- nephrotoxicity
isoflurane dose induction
3-5%
isoflurane maintainance dose
1.5-3%
sevoflurane induction dose
5-7%
sevoflurane maintainance dose
3.3-3.8%
desflurane side effects
more common than others
- resp tract irritation
- tachyacardia
which group of animals should methoxyflurane not be used in
reptiles, risk of nephrotoxicity
methoxyflurane is preferred to be used when
maintainence
