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Anesthesiology > Premedication Drugs > Flashcards

Premedication Drugs Flashcards

1
Q

Purposes of premedication

A
  1. Sedation, analgesia
  2. Anesthetic sparing effect
  3. Reduction of stress and catecholamine release
  4. Redution of O2 demand
  5. Increased safety for animals and staff
  6. Decrease parasympathetic tone
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2
Q

Drugs classes used in premedication

A
  1. Anticholinergics
  2. Alpha 2 agonists
  3. Phenothiazines and butyrophenones
  4. Benzodiazepines
  5. Opioids
  6. Antihistamines and antibiotics
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3
Q

MOA Anticholinergics

A

Inhibit parasympathetic nervous system

Antagonize muscarinic acetylcholine receptors

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4
Q

Anticholinergic drugs

A

Atropine and glycopyrrolate

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5
Q

Atropine

A

Lipid soluble
Absorbed well IM/SC/PO
Crosses BBB and placenta

Dose: 0.01-0.04 mg/kg IV

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6
Q

Glycopyrrolate

A

Water soluble
Absorbed slowly IM/SC/PO
Does not cross BBB and placenta

Slower than atropine, half the dosage

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7
Q

Indications for Anticholinergics

A

Need for increasing the heart rate (opioid induced or reflex bradycardia)
Need for decreasing salivation and bronchial secretions

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8
Q

Contraindications for Anticholinergics

A
  • Tachycardia
  • Hyperthyroidism
  • Most heart diseases
  • Narrow angle glaucoma
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9
Q

Cardiovascular side effects of Anticholinergics

A
  1. Second degree AV block (bradycardia and cardiac arrect)
  2. Tachycardia
  3. Hypertension
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10
Q

What part of the heart do Anticholinergics effect?

A

SA node particularly

AV node is weakly effected

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11
Q

Medetomidine/Atropine disadvantages

A

Vasoconstriction, tachycardia, hypertension

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12
Q

Other effects of anticholinergics

A
  1. Relaxes lower esophageal sphincter
  2. Mydriasis
  3. Bronchodilation
  4. Dries airway secretions
  5. intestinal paralysis
  6. CNS toxicity
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13
Q

What drug treats anticholinergic CNS toxicity?

A

Physostigmine

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14
Q

Which Anticholinergic is preferred in rabbits?

A

Glycopyrrolate

Atropine is broken down too quickly

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15
Q

Which class has the strongest available sedative ability?

A

Alpha-2 Agonists

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16
Q

Do Alpha-2 agonists have specific antagonists?

A

Yes

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17
Q

MOA: Alpha-2 agonists

A

Competitive agonist of alpha-2 receptor (suppress NE release)

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18
Q

Location of alpha-2 receptors

A
  1. CNS presynaptic membrane
  2. Postsynaptic membrane
  3. Extra-synaptic sites
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19
Q

Alpha-2 agonist presynaptic effects

A
  1. Sedation
  2. Analgesia
  3. Reduction of sympathetic outflow from brain
  4. Reduction of stress response
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20
Q

Alpha-2 agonist postsynaptic effects

A

Vasoconstriction of arteries and veins

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21
Q

Alpha-2 agonist extra synaptic effects

A
  1. Inhibition of lipolysis
  2. Inhibition of insulin release- hyperglycemia
  3. Natural ligand with Epinepherine
  4. Interaction with stress response
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22
Q

Alpha-2 agonist CNS effects

A
  1. Species specific sedative (weak in pigs)
  2. Some analgesia- synergism with opioids
  3. Muscle relaxation
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23
Q

Alpha-2 agonist Cardiovascular effects

A
  1. Strong vasoconstriction- high SVR and BP
  2. Reflex bradycardia- low CO and tissue perfusion
  3. May develop hypotension
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24
Q

Should alpha-2 agonists be used with atropine?

A

No- reflex bradycardia does not need to be treated

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25
Q

Alpha-2 agonist Respiratory effects

A
  1. Mild respiratory depression (decreased RR)
  2. Increase in tidal volume
  3. Increased upper airway resistance
  4. V/Q mismatch in horses and ruminants- decreased PaO2
  5. Bronchoconstriction, lung edema, and hypoxemia in Ruminants
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26
Q

Which alpha-2 agonist is contraindicated in sheep?

A

Xylazine

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27
Q

Alpha-2 agonist GI effects

A
  1. Decreased salivation
  2. Decreased lower esophageal sphincter tone
  3. Decreased GI motility
  4. May induce vomiting- esp cats
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28
Q

Xylazine side effect in cattle

A

Uterine contractions and abortion

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29
Q

Alpha-2 agonist indications

A
  1. Sedation of aggressive animmals
  2. Sedation in the ICU
  3. Sedation to manage post-op airway obstruction
  4. Prevention/tx of seizures
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30
Q

Alpha-2 agonist contraindications

A
  1. Too young or too old
  2. Hemodynamic instability
  3. Severely debilitated patient
  4. Not suitable for most at risk patients
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31
Q

Alpha-2 agonist drugs

A
  1. Xylazine
  2. Medetomidine
  3. Dexmedetomidine
  4. Detomidine
  5. Romifidine
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32
Q

Alpha-2 antagonist drugs

A
  1. Atipemezole
  2. Yohimbine
  3. Tolazoline
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33
Q

Which alpha-2 antagonist should be used to counteract alpha-2 agonist drugs?

A

Atipemezole

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34
Q

Alpha-2 antagonist are always given what route?

A

IM

Emergency can be given IV

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35
Q

Which alpha-2 antagonist is the most specific?

A

Atipemezole

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36
Q

Xylazine dosages

A

Cattle ~10% of horses dose

Small ruminants between dog and horse dose

37
Q

Xylazine duration

A

20-40min

38
Q

Detomidine species used

A

Large animals

39
Q

Detomidine route and duration

A

IM/IV/sublingual

90-120min

40
Q

Romifidine species used

A

Horses

41
Q

Romifidine route and duration

A

IM/IV

45-90min

42
Q

Romifidine benefits

A

Produces less ataxia than xylazine and is preferred for standing procedures

43
Q

Medetomidine dosing

A

USA- body surface
EU- body weight

Typically used in combination to reduce doses/adverse effects

44
Q

Dexmedetomidine is ______ times as potent as medetomidine.

A

2x

45
Q

Does dexmedetomidine have the same effects as medetomidine?

A

Yes

46
Q

Medetomidine is a mixture of which two drugs?

A

Levomedetomidine and Dexmedetomidine

47
Q

Phenothiazine drugs

A

Acepromazine, chlorpromazine, etc.

48
Q

Which receptors do phenothiazines act on?

A

Dopamine, serotonine, alpha-1, histamine

49
Q

Acepromazine duration

A

4-8 hours depending on dose

48 hours for liver patients

50
Q

Phenothiazine CNS effects

A
  1. Sedation (weaker than apha-2 agonists)
  2. No analgesia
  3. Antiemetic
  4. Mild respiratory depression
51
Q

Phenothiazine Cardiovascular effects

A

Vasodilation and hypotension (esp in hypovolemic animals)

Monitor bp very closely

52
Q

Phenothiazine Other effects

A
  1. Antihistamine
  2. Antiarrhythmogenic
  3. Inhibit platelet function
  4. Penile prolapse in horses (not much of an issue but avoid anyway)
  5. Seizures (older drugs)
53
Q

Phenothiazine indications

A
  1. Mild sedation for premed or post-op
  2. prevention/treatment of opioid dysphoria
  3. Prevention of emesis (morphine induced)
  4. Sedation for dogs with laryngeal paralysis
  5. Enhance xylazine in horses
54
Q

Contraindications for phenothiazines

A
  1. Hypovolemia or hemodynamic instability
  2. Age extreme patients
  3. Von-Willebrand disease
  4. Boxers
  5. Breeding stallions
55
Q

Butyrophenones are very similar to which other class?

A

Phenothiazines

56
Q

Butyrophenone drugs

A

Droperidol and azaperone

57
Q

T/F: Butyrophenones are more likely to cause behavioral side effects.

A

True

58
Q

T/F: Butyrophenones are more likely to cause the same adverse effects as phenothiazines.

A

False, they cause less profound of the same side effects

59
Q

Benzodiazapine MOA

A

GABA receptor agonists

60
Q

Benzodiazapine effects

A

Sedative, anticonvulsant, muscle relaxant

Minimal CV and respiratory effects

No analgesia

61
Q

Benzodiazapine drugs

A

Agonists- diazepam, midazolam, zolazepam

Antagonists- flumazenil, sarmazenil

62
Q

Premedication mixtures with benzos

A

Opioids, alpha-2 agonists or both

63
Q

Induction mixtures with benzos

A

Dissociative anesthetics, barbituates, propofol

64
Q

Diazepam characteristics

A
  • Lipid soluble
  • Formulated in propylene glycol or lipid emulsion
  • low chemical compatibility
65
Q

Diazepam administration

A

Slowly IV

Poor absorption and pain on IM injection

66
Q

Diazepam duration and metabolism

A

Metabolized in liver

1-4 hours

67
Q

Midazolam characteristics

A
  • Water soluble

- Good chemical compattibiliy

68
Q

Midazolam differences from diazepam

A
  • More potent
  • Shorter acting
  • Inactive metabolites
  • Can be given IM/IV or MM
69
Q

Opioid receptors

A

Mu: strong analgesia, respiratory depression, dependency
Kappa: weaker analgesia
Sigma: weaker analgesia

Location: brain, spinal cord, peripheral nerves, inflamed organs

70
Q

Opioid classifications

A

Full agonists: activate receptors and trigger full tissue response
Partial agonists: activate receptors but do not trigger full tissue response even at high doses
Antagonists: bind to receptors but do not activate them

Concentration dependent

71
Q

Opioid CNS effects

A
  1. Analgesia (acute pain)
  2. Decreasing MAC of inhalants (species dependent)
  3. Sedation (better with more pain)
  4. Excitation, dysphoria
  5. Tolerance
  6. Dependence
72
Q

Opioid vomiting mechanisms

A

Stimulation of chemoreceptor trigger zone outside the BBB

After entering the brain they will inhibit the vomiting center

Water soluble > lipid soluble

73
Q

Opioid cardiovascular effects

A

No direct negative inotropy or vasodilation

May reduce sympathetic outflow and indirectly reduce BP

Increase parasymathetic tone to decrease HR

Suitable risk for most patients, improves Cv function be allowing reduction in anesthetic doses

74
Q

Opioid respiratory effects

A

Depression of respiration not as strongly as humans/primates

Antitussive effects, may inhibit airway protective reflexes

75
Q

Opioid GI effects

A

Nausea, vomiting, defecation, obstipation, spasm of the sphincter or oddi

76
Q

Opioids other effects

A 
Hypothermia
Post off hyperthermia
Myosis in dogs, mydriasis in cats
Inhibition of urination
Noise sensitivity
77
Q

Opioid indications

A

Premedication
Perioperative analgesia
Treatment of acute and chronic pain

78
Q

Opioid administration

A

ALL THE WAYS

79
Q

Morphine

A
  • cheap and strong analgesic
  • water soluble
  • Slow onset, long duration
  • High individual variety in elimination
  • metabolized in liver
  • may case histamine release esp in high doses
80
Q

Hydromorphone, oxymorphone

A
  • Strong analgesics (full mu)
  • duration ~4hr
  • Reliable metabolism
  • better choice than morphine
81
Q

Methadone

A

Similar to hydromorphone

Also acts as NMDA antagonist

82
Q

Fentanyl

A
  • Strong analgesic (full mu agonist)
  • fast onset of duration
  • may accumulate after long infusions
  • bolus or CRI dosages
83
Q

Remifentanil

A
  • Similar to fentanyl with potentcy
  • Short acting and does not accumulate
  • disruption of administration may trigger strong pain
  • boluses may cause sudden bradycardia
84
Q

Butorphanol

A
  • Partial antagonist on mu and kappa (mau antagonize full mu agonists)
  • weak and short acting analgesic
  • may worsen pain
  • used for premed w/ benzodiazepines or alpha-2 agonist
85
Q

Buprenorphine

A
  • partial mu agonist
  • stronger analgesic than butorphanol
  • long acting slow onset
  • often used in cats (less excitement and easy admin)
86
Q

Tramadol

A
  • weak analgesic
  • inhibits NE and serotonin reuptake
  • not scheduled
  • can be given PO
87
Q

Opioid antagonists

A

Naloxone: small animals to reverse respiratory depression

Naltrexxone: long acting, antagonize wild animals after long acting opioids

88
Q

Antibiotics

A
  • Cefazolin
  • Amoxicillin clavulic acid

Give IV 20min pre-op and every 90-120min

89
Q

Antihistamines

A

Diphenhydramine: H1 antagonist

H2 antagnoist: ranitidine, famotidine, cimetitide- increase pH of stomach

Given pre-men for mast cell tumor removal

Anesthesiology (27 decks)

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