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Flashcards in Sedation and premedication Deck (54)
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1

Define premedication

Administration of medication prior to anaesthesia:
- facilitate/improve peri-anaesthetic period
- long acting drugs may span the whole period
- animals should be maintained under observation

2

Aims of premed

Reduce anxiety
Facilitate handling
Peri-operative analgesia
Facilitate smooth anaesthetic induction, maintenance and recovery
Reduce dose (anaesthetics)
Reduce risks of specific complications

3

Why are anti-cholinergics used a premeds?

Less commonly nowadays but to reduce secretions. Also: used when there was:
- increased vagal tone
- vagomimetic drugs (opioids)
- ressuscitation
- adjuncts to antagonism of mm blockers

4

Major effects - anticholinergics - 5

Increased HR
Bronchodilation
Decreased secretions (more viscous)
Mydriasis
Reduced GIT motility

5

2 examples - anti-cholinergics

ATROPINE: crosses BBB (remember rabbits have atropine esterase)
GLYCOPYRROLATE: lower magnitude increase in HR (than atropine), longer acting (1 hour), not licensed in animals

6

Define anxiolytic

calming effect, less interest in environment, still aroused by stimuli, AKA tranquilisers/nebulisers (not same but often used interchangeably)

7

Define sedative

calming effect, less responsive to stimuli, sleepiness, may also be analgesics

8

Define narcosis

drug-induced sleep, not easily aroused

9

Define hypnosis

artificially-induced sleep, broader meaning

10

List the 5 classes of sedatives

Phenothiazines
Butyrophenones
Benzodiazepines
Alpha-2 adrenergic agonists
(opioids?)

11

Describe phenothiazines

Highly protien bound (>90%)
Lipophilic (cross placenta and BBB)
Hydrophilic (IM absorption)
Hepatic metabolism
Excretion - urine and bile

12

Effects - Phenothiazines -8

CALMING - main reason for use, blocks CNS dopamine-R
POTENTIATE CNS DEPRESSION (of other drugs): opioids, anaesthetics
EXTRAPYRAMIDAL EFFECTS - high doses
PERIPHERAL VASODILATION: blocks alpha-1 adrenergic receptors
ANTI-EMETIC EFFECT: inhibits CRTZ
ANTI-HISTAMINE EFFECTS: blocks H1 receptor
ANTI-MUSCARINIC EFFECTS: antispasmodic in GIT
HYPOTHERMIA: depression of thermoregulatory centre, increased vasodilation --> heat loss

13

List 3 examples of phenothiazines

ACEPROMAZINE (ACP)
PROMETHAZINE
CHLORPROMAZINE

14

Which phenothiazine is the only phenothiazine licensed in animals?

Acepromazine (ACP)

15

When is promethazine used?

ACTIONS:
anti-histamine
For nausea, vomiting, motion sickness (human)

16

Advantages - acepromazine -3

- Anxiolytic (low dose) OR sedative (higher dose)

- Anti-arrhythmic: reduce SNS activity, membrane stabilising effects (LA effect), blockade of cardiac alpha adrenergic receptors

- PO administration - variable absorption

17

Disadvantages - acepromazine - 12

HYPOTENSION - blocks alpha 1 adrenergic receptors, suppresses SNS

SYNCOPE - due to hypotension and bradycardia, brachycephalics more susceptible (naturally high vagal tone and upper airway obstruction)

CARDIAC SPHINCTER RELAXATION: anti-muscarinic effect --> increases risk of reflux and regurgitation

DECREASED PCV and TS - due to splenic sequestration OR vasodilation causing an increased intravascular space volume with consequent RBC dilution

LATE ONSET OF ACTION

LARGER ANIMALS MORE SENSITIVE

CONCOMITANT USE OF ADRENALINE - ACP blocks alpha1 receptors --> vasodilation. Adrenaline may lead to unopposed beta2 activity --> vasodilation.

(SEIZURE THRESHOLD - reduced)

ANTI-THROMBOTIC - due to decreased platelet count, inhibit aggregation, transien

AVOID USE PRIOR TO INTRADERMAL SKIN TESTING

MAY POTENTIATE EFFECTS OF ORGANOPHOSPHATES

RELAXATION OF RETRACTOR PENIS MUSCLE IN HORSES

18

When should you avoid acepromazine?

Age extremes (BP regulation problems)
Renal/hepatic disease
Hypovolaemia/most shock states
Brachycephalics
Breeding stallions

19

Where do BUTYROPHENONES work?

Same receptors as Phenothiazines - but degree of localisation on specific receptors is variable. They have a sedative action due to dopamine antagonism. Also has anti-emetic properties and causes vasodilation and hypotension.

20

When are butyrophenones used?

Pigs, healthy animals
Sedation and behavioue modification

21

Pharmacodynamics - azaperone

Peak sedation in 15-30 mins (IM)
Sedation duration 2-3 hours
Decrease HR, CO, ABP
Impaired thermoregulation

22

What is the metabolism/excretion of azaperone?

Hepatic metabolism --> inactive metabolites
Renal excretion

23

What class of sedatives does azaperone belong to?

Butyrophenones

24

What can azaperone be combined with?

Ketamine --> immobilisation, anaesthesia
Opioids: for painful diagnostic or minor surgical procedures

25

Define neuroleptoanalgesia

a state of quiescence, altered awareness and analgesia produced by a combination of an opioid analgesic and a neuroleptic

26

List 2 examples of neuroleptoanalgesic mixtures

HYPNORM: fluanisone and fentanyl
INNOVAR VET: droperidol and fentanyl
IMMOBILON: acepromzaine and etorphine, extremely potent, immobilisation of large wild animals

27

Are benzodiazepines licensed for vet use in the UK?

No

28

List 3 commonly used benzodiazepines

Diazepam
Midazolam
(Zolazepam)

29

How do benzodiazepines work?

Act of GABA-A receptor: allosteric modulation, increased affinity/active of GABA therefore increased inhibitory NT conductance.

30

Main actions - benzodiazepines - 4

Anticonvulsant
Anxiolytic/sedative
Skeletal mm relaxation (minor)
Amnesiac (anterograde)

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