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My 2016 RUSVM Anesthesia > Premedication Dr. Ambrisko > Flashcards

Premedication Dr. Ambrisko Flashcards

1
Q

what is sedation

A

induction of CNS depressioun & drowsiness by use of drugs (not unconsciousness)

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2
Q

What is tranquillization

A

used somewhat synonymously to sedation

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3
Q

what is analgesia

A

aka antinociception

loss or reduction of pain sensation

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4
Q

what is general anesthesia

A

controlled & reversible loss of consciousness, nociception & mobility

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5
Q

what is balanced anesthesia

A

using multiple drugs to achieve the goals of general anesthesia w/ less side effects than using a single agent (e.g. a combo of an anesthetic, analgesic & muscle relaxant)

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6
Q

what is dissociative anesthesia

A

form of general anesthesia characterized by a catatonic state

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7
Q

what is neuroleptanalgesia

A

state similar to general anesthesia produced by a sedative & an analgesic agent (e.g. phenothiazine + opioid)

  • very deep sedation + very deep pain mgmt*
  • usually no unconsciousness*
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8
Q

what is inhalationa anesthesia

A

general anesthesia using inhalational drugs

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9
Q

what is TIVA

A

Total Intravenous Anesthesia

achieved soley by injectable drugs

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10
Q

what is PIVA

A

combination of injectable drugs & lower concentration of inhaled anesthetic agent

basically balanced anes!

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11
Q

what is local anesthesia

A

loss of sensation in a smaller, circumscribed body area

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12
Q

what is regional anethesia

A

loss of sensation in larger but limited body area

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13
Q

what is purpose of premedication

A

sedation & analgesia

anesthetic sparing effect

reduction of stress & catecholamine release

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14
Q

types of premedication d2rugs

A

anticholinergics

alpha2 agonists

phenothiazines & butryophenones

benzodiazepines

opiods

muscle relaxants

antihistamines & antibiotics

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15
Q

what do anticholinergics do

name 2

A

inhibit PSNS

antagonists on muscarinic ACh receptors

Atropine

Glycopyrrolate

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16
Q

Atropine

solubility

route

A

crosses BBB & placental barrier

lipid soluble

IM, SC, PO, IV

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17
Q

Glycopyrrolate

solubility

route

A

onset slower & duration longer than atropine

doesn’t cross BBB & placenta

H2O soluble

IM SC, PO

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18
Q

indications for use of anticholinergics

A

Routine use not recommended

incr HR

  • opioid induced bradycardia*
  • tx of reflex bradycardia*
  • young & brachycephalic breeds*

decr salivation & bronchial seccretion

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19
Q

contraindications for anticholinergics

A

tachycardia

hyperthyroidism

most cardiac dz except when tx bradycardia

narrow angle glaucoma

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20
Q

CV side effects of anticholinergics

A

2° AV block

bradycardia

cardiac arrest

tachycardia

hypertension

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21
Q

what happens if you combine an alpha2 agonist + atropine

A

vasoconstriction

tachycardia

hypertension

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22
Q

T or F

Routine co-administration of an alpha2 agonist & anticholinergic is contraindicated

A

TRUE!

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23
Q

other effects of anticholinergics

A

relaxes lower esophageal sphincter (regurg)

mydriasis (may trigger acute glaucoma)

bronchodilation (increases airway dead space)

dries airway secretions

Intestinal paralysis (may cause colic in horses)

CNS toxicity: crosses BBB may cause sedation, coma

Tx w/ physostigmine (not neostigmine)

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24
Q

What is special about rabbits & atropine

A

most rabbits have high levels of atropinase enzyme so atropine not effective

Glycoyrrolate is preferred!

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25
Q

What are alpha2 agonists

MoA

A

strongest available sedatives (except pigs)

have important CV side effects

have specific antagonists

competitive agonist of alpha2 adrenergic receptors

suppress NE release by negative feedback

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26
Q

what are effects of alpha2 receptors

A

cause sedation

analgesia

reduction of sympathetic outflow from brain

decr stress response

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27
Q

where are important (to anesthesia) alpha2 receptors located & what do they do

A

wall of arteries & veins (along with alpha1) - mediate vasoconstriction

pancreas ß cells - inhibit insulin release ⇒ hyperglycemia

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28
Q

what are CNS effects of alpha2 agonists

A

sedative effect spp specific:

strong: dogs, cats, horses, ruminants

weak: pigs (alpha2 + benzo + opioid best combo)

some anlagesic effects synergistic w/ opioids

muscle relaxation

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29
Q

what are CV effects of alpha2 agonists

A

strong vasoconstriction ⇒ reflex bradycardia ⇒ low CO & tissue perfusion

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30
Q

what are respiratory effects of alpha2 agonists generally

in horses

A

mild respiratory depression

In horses: upper airway resistance increases

  • relaxation of larynx, pharynx & narse
  • head dropping in horses: nasal edema
  • V/Q mismatch
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31
Q

what are respiratory effects of alpha2 agonists in ruminants

A

Bronchoconstriction

V/Q mismatch

lung edema & hypoxemia

any alpha2 in any ruminant spp

xylazine in sheep is contraindicated

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32
Q

xylazine spp differences, issues

duration

A

Equine: better than for other spp

intraarterial injection may cause excitement (seizure) Don’t do it!

Cattle: sensitive ≈ 10% of horse dose needed

may cause uterine contraction & abortion in cattle

Dogs: less preferred alpha2 for this spp

duration: 20-40 min

33
Q

indications for use of alpha2 agonists

A

sedation of aggressive animals

34
Q

contraindications for alpha2 angonists

A

hemodynamic instability

not suitable for risk patients

35
Q

Alpha2 agonists/antagonists (reversal agents)

A

Xylazine/Yohimbine (LA w/ exceptions)

Dexmdetomidine/Atipamezole

Medetomidine

Detomidine

Romifidine

36
Q

In the order of highest to lowest, what are the alpha2/alpha1 receptor specificity of the alpha2 agonists?

A

Dexmedetomidine >>> detomidine > xylazine

the main effects are very similar even with the specificity differences

37
Q

In the order of highest to lowest, what are the alpha2/alpha1 receptor specificity of the alpha2 antagonists?

A

atipamezole >>> yohimbine >> tolazoline

yohimbine & tolazoline are “dirty drugs” acting on other receptors & have many side effects

Use atipamezole to antagonize any alpha2 agonist whenever possible, give IM except for emergency (IV)

38
Q

Medetomidine

A

Not available in US

50:50 racemic mix of demedetomidine & levomedetomidine

Dexmedetomidine 2 x as potent as medetomidine

39
Q

Dexmedetomidine

A

most specific drug for alpha2 receptors

mostly for SA use but may be used in horses

40
Q

Detomidine

RoA

Duration

A

LA use

IM, IV, sublingual

90-120 min

41
Q

Romifidine

use

RoA

duration

A

used in horses

IM, IV

45-90 min

thought to produce less ataxia than xylazine, preferred for standing dental surgery

42
Q

Alpha2 agonists In order of duration of action (minutes) from shortest to longest

A

Xylazine (20-40) < Romifidine < (45-90) < Detomidine (90-120) < Dexmedetomidine (30-120)

43
Q

What are the premeds in the phenothiazine class

how do they work?

A

Acepromazine

Chlorpromazine, etc

antagonist of multple receptor types:

Dopamine

Serotonin

Alpha1

Histamine

44
Q

Acepromazine

duration of action

A

4-8 hours

48 hours in liver pts

45
Q

CNS effects of phenothiazines

A

weaker sedative effects compared to alpha2 agonists

NO analgesic effect

antiemetic

mild respiratory depression

46
Q

CV effects of phenothiazines

A

Alpha1 antagonist:

causes vasodilation & hypotention

47
Q

other effects of phenothiazines

A

antihistaminic

anty arrhythmogenic

inhibits platelet function

Penile prolapse in horses

seizures?

48
Q

Indications for phenothiazines

Contraindications

A

mild sedation for premed or post op

prevent/tx opioid dysphoria

prevent emesis by morphine

sedation of dogs w/ laryngeal paralysis

enhance sedation of xylazine in horses

  • Hypovolemia/hemodynamic instability*
  • vWD in dobes*
  • Boxers (bradycardia)*
  • Breeding stallions (penile prolapse)*
49
Q

What drug family is similar to phenothiazines

drugs in family

spp most used with

effects/side effects

A

Butyrophenones

Droperidol & azaperone (Stresnil®)

Azaperone used for Pigs

sedative similar to aceprom

less hypotensive, stronger antiemetic than aceprom

less platelet effect

antiarrhythmogeni, not seizurogenic

More likely to cause behavioral side effects

50
Q

Characteristics of benzodiazepines

A

GABA receptor agonists

Sedative, anticonvulsant, muscle relaxant effects

Minimal CV & respiratory effects

NO ANALGESIA!

51
Q

What are GABA receptors

A

GABA main inhibitory neurotransmitter in CNS

Benzodiazeines allosterically activate (no maximal effect)

Site of most anesthetics (notable exception is ketamine!)

52
Q

Benzodiazepines used in vet med

A

Agonists

Midazolam

Diazepam

Zolazepam (Zoetil or Telazol)

Antagonists

Flumazenil

53
Q

spp specific sedation effects of benzos

A

Dogs, cats, horses: disorientation, excitation may occur when used alone

Better sedative effects in ruminants, camelids, pigs, birds & ferrets

Rarely used alone

54
Q

indications for use of benzos

A

as Premed:

Combine with opiods a/o alpha2 agonists

for Induction:

Combine w/ dissociatives, barbiturates or propofol

Tx of seizures

55
Q

Diazepam characteristics

RoA

duration

cautions

A

Lipid soluble

formulated in propylene glycol or lipid emulsion

chemical compatibility limited

IV, poor absorbtion & pain IM

hepatic metabolism

1-4 hours

Oral may cause liver damage in cats

56
Q

Midazoam characteristics

RoA

duration

caution

A

Water soluble (no propylene glycol)

Good chemical compatibility

more potent than diazepam

hepatic metabolites inactive

IM, IV or TM

57
Q

Opioid characteristics

A

strongest available systemic analgesics

best choic for tx of acute pain

decr anesthetic dose

MINIMAL CV effects

Suitable for most risk pts

58
Q

Types of opioid receptors

A

Mu (µ): strong analgesis, resp. depression, dependency

Kappa (K): weaker analgesia

Delta (ð): weaker (human)

59
Q

classification of opioids

A

Full agonists: activate receptors & trigger full tissue response

Partial agonists: activate receptors but do not trigger full tissue response even at high doses (butorphanol)

Antagonists: bind to receptors but do not activate them

Mixed agonist antagonist: activate one receptor type & inhibit another one

e.g. Butorphanol mu antagonist & kappa agonist

60
Q

CNS effects of opioids

A

Analgesia

decr MAC

spp dependent:

primates > dogs > cats > pigs > horses

may incr MAC in horses!

61
Q

T or F

Opioids may trigger or inhibit vomiting

A

TRUE

stimulate CRTZ outside BBB triggering vomiting then cross BBB & inhibit

water soluble opioids (morphine) enter BBB slowly: cause more vomiting

lipid soluble (fentanyl) enter BBB fast: no vomiting

62
Q

CV effects of opioids

A

Minimal CV effects

No direct negative inotropy or vasodilation

Suitable for most risk pts

63
Q

Respiratory effects of opioids

A

May depress

Antitussive effect

May inhibit airway protective reflexes (coughing)

64
Q

GIT effects of opioids

A

defecation

obstipation

65
Q

Other effects of opioids

A

Hypothermia

Cats: post OP hyperthermia

Myosis (dogs), mydriasis (cats)

inhibition of urination

noise sensitivity

66
Q

indications for opioids

A

Premedication alone or in combo

Perioperative analgesia

Tx acute & chronic pain

67
Q

RoA of opioids

A

IM, SC

IV/CRI

PO

Epidural/spinal

Transdermal (fentanyl)

Oral (buprenorphine for cats)

68
Q

Morphine

A

Preferred

full mu agonist

water soluble

slow onset (30-45min) long duration (4-6 hr)

May cause hitamine release esp post high IV dose

69
Q

hydromorphone, oxymorphone

A

full mu agonist

4 hr duration

No histamine release

70
Q

Methadone

A

similar to hydromorphone

also acts as NMDA antagonist!

71
Q

Fentanyl

A

full mu agonist

fast onset, short duration (15-20 min)

no histamine release

may accumulate after long infusions

72
Q

Remifentanil

A

similar potency to fentanyl

very short acting (5 min), does not accumulate

73
Q

Butorphanol

A

mu antagonist, kappa agonist

may worsen pain in case of strong pain

weak & short acting analgesic

may antagonize full mu agonists

74
Q

Buprenorphine

A

partial mu agonist

stronger analgesic than butorphanol but weaker than full mu

slow onset (20-40min IV) long acting 6-8 hours

often given to cats because may cause less excitation than full mu agonists

Owners can give TM

75
Q

Tramadol

A

Weak analgesic

hepatic metabolite is mu opioid agonist

tramadol itself inhibits NE & serotonin reuptake (analgesia)

PO

76
Q

Opioid antagonists

A

Naloxone

30 min duration

Naltrexone

long acting (≈10 hrs)

used to antagonize wild animals after long acting opioids e.g. carfentanyl or etorphine

77
Q

Muscle relaxants

A

Centrally acting:

Guaifenesin

Peripherally acting

NMBD’s

Dantrolene

78
Q

Guaifenesin

A

aka glyceryl guaiacolate (GG)

large animal anesthesia

minimal CV or resp effects

NO ANALGESIA or Unconsciousness SHOULD NOT be used as sole agent!

most common: 5% GG in dextrose

>10% = thrombophlebitis

Part of TIVA “Triple Drip” : GG + alpha2 + ketamine

79
Q

Dantrolene

A

muscle cells

used for tx Malignant hyperthermia (pigs mainly)

My 2016 RUSVM Anesthesia (22 decks)

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