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POS 2 > Premedication and sedation > Flashcards

Premedication and sedation Flashcards

1
Q

What are the 4 phases of anaesthesia?

A

premedication
induction
maintenance
analgesia

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2
Q

What are the concepts of balanced anaesthesia?

A

unconsciousness
myorelaxation
immobility
analgesia

transient loss of memory
maintenance of physiological function

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3
Q

What are the goals of premedication?

A

relieve fear and anxiety
make patients more amenable to handling
reduce stress-hormone release
form part of the balanced anaesthesia

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4
Q

What can reducing stress-hormone release also reduce?

A

catecholamine induced cardiac-arrhythmias

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5
Q

How is premedication a part of balanced anaesthesia?

A

it smooths the induction, decreased induction and maintenance anaesthetic doses, facilitate smooth recovery
provides analgesia
provides muscle relaxation
reduces unwanted autonomic reflexes

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6
Q

How can we optomise premedication?

A

know drugs and interactions
tailored approach: individual needs, procedural requirements
combinations: decrease dose of drugs, decrease secondary effects, optimal combo of desired effects
reversibility

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7
Q

What are the categories of drugs that can be used for premedication?

A

alpha2 agonists
phenothiazines
benzodiazepines
opioids
anticholinergics
induction agents

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8
Q

What is acepromazine (ACP)?

A

a phenothiazine derived tranquilizer

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9
Q

What are the wanted effects of ACP as a premedication?

A

sedation
anxiolysis (in hospitalised ptx)
anti-emetic
anti-arrhythmic (lowers BP)
antihistaminic
NO ANALGESIA

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10
Q

What is the mechanism of action of ACP?

A

acts on various receptors with inhibitory effect on the brain serotoninergic, H1, dopaminergic, alpha1

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11
Q

What are the CV and Resp effects of ACP?

A

CV: vasodilation/hypotension, syncope, anti-arrhythmic
Resp: minimal, increased when used w/ opioids

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12
Q

What are other effects, unwamted effects ACP could have?

A

pro- or anticonvulsant
anticholinergic
hypothermia
haematological: decrease in PCV, splenic dilation, anti-thrombotic
anti-oxidant
anti-inflammatory

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13
Q

What are the properties of ACP?

A

highly protein bound
lipophilic, cross BBB and placenta
hepatic metabolism
long duration of action
no reversal agent
at high doses, extrapyramidal effects may be seen (increased locomotor activity and uncontrollable restlessness)

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14
Q

What is the onset and duration of action of ACP?

A

onset: 30-40 min IM
duration: begins to wane 3-4h, lasts up to 6-8h (dose-dependant)

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15
Q

For which type of ptx is ACP?

A

all healthy young adults (dogs, cats, horses)
more reliable sedation in dogs

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16
Q

When should we avoid or use ACP with caution?

A

non-corrected hypovolaemia/hypotension
severe renal dz
severe liver dz
HCM/left ventricular hypertension

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17
Q

What are alpha2 adregergic agonist molecules?

A

medetomidine, dexemedetomidine (Ca, Fe)
Romifidine (Eq)
Detmonidine, Xylazine (Eq, Bov)
Clonidine (Hum)

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18
Q

What is the mechanism of action of alpha2 adrenergic agonists?

A

a2 receptors are a sub-class of both pre-and post-junctional noradrenergic receptors
effects mediated via central and peripheral a2 receptors

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19
Q

What are the effects of alpha2adrenergic agonists mediated vial central a2 receptors?

A

sedation and anxiolysis
sympatholysis
anaesthetic sparing
muscle relaxation
analgesia

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20
Q

What are the effects of alpha 2 adrenergic agonists mediated via peripheral a2 receptors?

A

vascular smooth muscle vasoconstriction

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21
Q

What are the effects of alpha2 adrenergic agonists?

A

CV: BP, HR, CO
Resp: minimal, increased w/ opioids
renal system
pancreas
liver
body temp
emesis
uteribe, GI tract, ocular effects

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22
Q

What are the properties of alpha2 adrenergic agonists?

A

selectivity of alpha2/alpha1 ratio
highly lipophilic: easily cross BBB, placeta, mms
rapid absorption
metabolism mainly in liver: oxidative and hydrolytic breakdown

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23
Q

What are the main aspects of alpha2 adrenergic agonists to remember?

A

good analgesia (spinal)
reliable sedation in dogs and cats and in a variety of others
reversable
arrhythmogenic
increase/decrease BP
more expensive

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24
Q

For which patients is alpha2 adrenergic agonists considered for premedication?

A

healthy young dogs as premed or to sedate for short ambulatory procedures
aggressive dogs and cats for IM sedation
for many non-conventional species

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25
Q

When should we avoid or use with caution alpha2 adrenergic agonists?

A

cardio-resp diz/impairment
diabetic patients
in general sick animals classified ASAIII or more

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26
Q

What are the commonly known benzodiazepines used in vet med?

A

midazolam and diazepam

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27
Q

What is the mechanism of action of benzodiazepines?

A

enhance the activity of GABA in the CNS

28
Q

What are the main effects of benzodiazepines?

A

anticonvulsant
anxiolytic and sedative
muscle relaxation (skeletal)
amnesic (anterograde and maybe retrograde)
NO ANALGESIA

29
Q

When are benzodiazepines used as an anticonvulsant?

A

first line tx in status epilepticus

30
Q

What are the anxiolytic and sedative characteristics of benzodiazepines?

A

good sedation in neonates and geriatric or sick dogs and cats
not good sedative in adults
may cause disinhibition: excitation

31
Q

What are the other unwanted effects of benzodiazepines?

A

hepatic problems
CV depression (minimal)
resp depression (minimal)
antagonists are expensive

32
Q

How can benzodiazepines affect hepatic problems?

A

PO in cats have been associated with fulminant hepatic failure
if hepatic dz and hypoproteinaemia, increase free drug and potential for overdose
liver enzyme induction

33
Q

How can benzodiazepines affect respiratory depression?

A

with higher doses relaxation may result in decreased resp function and when combines with anaesthetics
reduced ventilatory response to CO2

34
Q

What are the physical-chemical properties of midazolam?

A

contains an imidazoline ring
opens in acidic solution(ph<4) and molecule becomes water soluble
closes when in the body pH
acidic water soluble formulation doesnt require solubilising agents

35
Q

What are the physical-chemical properties of diazepam?

A

is liposoluble
solubilised in emulsion or propylene glycol
IV use only
propylene glycol may cause arrhythmias, haemolysis, hypotension

36
Q

What are the properties of benzodiazepines?

A

highly protein bound
hepatic metabolism (potential for entero-hepatic recycling and cumulative effects)
midazolam has no active metabolites, shorter action, suitable for infusion

37
Q

For which patients are benzodiazepines used for?

A

neonates up to 4 weeks
very old or sick dogs and cats
ptx with risk o seizure
in case of severe cardiac impairment
when myorelaxation is needed

38
Q

When to avoid or use with caution benzodiazepines?

A

healthy young/adult non-premedicated animals
hepatic encephalopathy

39
Q

What are examples of endogenous opioids?

A

endorphins, dynorphins, enkephalins
produced by body

40
Q

Why do we use exogenous opioids?

A

gold standard, very powerful analgesic
treatment of moderate-severe pain
is a controlled drug

41
Q

What are the types of receptor agonists in opioids?

A

mu
kappa
delta

42
Q

What are examples of mu receptor agonist opioids?

A

methadone
morphine
fentanyl
pethidine

43
Q

What are examples of kappa receptor agonist opioids?

A

butorphanol (pethidine, morphine)

44
Q

What are examples of delta receptor agonist opioids?

A

etorphine (morphine, buprenorphine)

45
Q

What is the opioid reversal agent?

A

naloxone

46
Q

What are the effects of mu receptor agonist opioids?

A

Analgesia (profound)
sedation/narcosis (mild)
sympatholytic: decreases HR
euphoria/increased locomotor activity
nausea/vomiting/constipation/decreased gut motility
respiratory depression/cough suppresion
dependence
miosis: dog and pig
mydriasis: horse and cat

47
Q

What are the effects of kappa receptor agonist opioids?

A

analgesia (mild-moderate)
sedation
dysphoria/increased locomotor activity

48
Q

What is morphine?

A

gold standard pure mu agonist potent opioid
not licensed in animals

49
Q

What is methadone?

A

pure mu agonist opioid
no histamine release if given IV
onset 10 min, duration 2-4h
licensed for dogs

50
Q

What is butorphanol?

A

kappa agonist and mu agonist opioid
mild sedative
poor analgesic!!
used with sedative drugs in horses and dogs
not controlled

51
Q

What is buprenorphine?

A

weak mu agonist opioid
licensed in SA
not as potent as morphine but better than butorphanol

52
Q

What is pethidine?

A

mu agonist opioid of short duration
licensed
must be given IM

53
Q

What is fentanyl?

A

very potent mu agonist short acting opioid
now licensed
used as an infusion during surgery

54
Q

What is naloxone?

A

antagonist vs opioid overdose

55
Q

For which patients should we give opioids?

A

all pts in pain
invasive sx
ptx with cardiac dz

56
Q

When do we use opioids with caution?

A

resp dz
allergic conditions, asthma
ptx with laryngeal dysfunction

57
Q

What are the options for sedation/premed?

A

opioid, acp, benzodiazepine or a2 agonist ALONE

opioid + acp
opioid + a2 agonist
opioid + benzo

58
Q

What are the anticholinergic agents?

A

atropine and glycopyrrolate
not in regular us in uk as premed

59
Q

When are anticholinergics mostly used?

A

treat excessive decrease of HR and as part of CPR

60
Q

What are the induction agents?

A

ketamine
alfaxolone
propofol

61
Q

What should we know about ketamine as an induction agent?

A

used as part of premed combos
effective for fractious animals

62
Q

What should we know about alfaxolone as a an induction agent?

A

used mainly in cats when other premed plan fails and/or as part of combo without IV access
volume large to prevent use in most dogs
off-license

63
Q

What should we know about propofol as an induction agent?

A

low dose IV for short procedures

64
Q

How is ketamine usually given as an induction agent?

A

IM
often combined with midazolam
or combined with medetomidine/dexemedetomidine

65
Q

How is alfaxolone usually given as an induction agent?

A

IM
often combined with midazolam
or combined with opioid (butor/methadone)

66
Q

How id propofol usually given as an induction agent?

A

slow IV
may be repeated

67
Q
A

POS 2 (10 decks)

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