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Intro to Anesthesiology > Preanesthetic Medications > Flashcards

Preanesthetic Medications Flashcards

1
Q

Many drugs are _____

A

Receptor mediated

- either agonists or antagonists

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2
Q

Most drugs that produce CNS depression are either _____ at inhibitory sites, or ____ at excitatory sites

A

Agonists; antagonists

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3
Q

Desired effect of most anesthetic type drugs

A

CNS

  • few drugs are 100% selective
  • most have adverse effects
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4
Q

Premeds

A

Drugs given before induction of anesthesia

  • individual drugs are rarely ideal
  • combinations are common
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5
Q

Indications

A
  • calm, sedate, chemical restraint
  • analgesia
  • decrease drug requirements
  • offset adverse drug effects
  • smooth induction/recovery
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6
Q

Factors in choosing premeds

A
  • temperament
  • desired effects
  • undesirable drug effects
  • pain involved
  • health status
  • type of practice
  • personal preferences
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7
Q

Classes of drugs

A
  • anticholinergics
  • tranquilizers
  • alpha-2-adrenergic agonists
  • opioids
  • neuroleptanalgesics
  • dissociatives
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8
Q

Anticholinergic - mechanism

A

Competitive antagonism of AcH at parasympathetic muscarinic cholinergic receptors

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9
Q

Anticholinergic - effects

A
  • increased heart rate
  • decreased secretions
  • decreased GI motility
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10
Q

Anticholinergic - indications

A
  • prevent or treat vagally mediated bradycardia

- decrease salivary and/or respiratory secretions

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11
Q

Atropine and glycopyrrolate are ______

A

Anticholinergic agents

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12
Q

Atropine

A

Crosses BBB and placenta

  • may be more likely to cause tachycardia
  • duration 0.5-1.5 hrs
  • hydrolyzed rapidly in some
  • useful in emergencies
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13
Q

Atropine cannot be used in _________

A

Ruminants or rabbits due to rapid hydrolyzation

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14
Q

Glycopyrrolate

A

Does not cross BBB or placenta

  • duration 2-4 hrs
  • less tachycardia
  • less effective
  • more expensive
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15
Q

Avoid anticholinergic agents in:

A
  • ruminants and horses due to effect on GI motility
  • animals with tachyarrhythmias
  • questionable in routine cases
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16
Q

Anticholinergic are parasymptholitic

A

Can’t use heartrate as an indicator of anesthetic depth

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17
Q

Tranquilizers

A
  • do produce calming
  • do not provide chemical restraint
  • do not provide analgesia
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18
Q

Acepromazine - mechanisms

A

Central antagonism of D2 dopamine receptors and H1 histamine receptors
- peripheral alpha-1 adrenergic blockade

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19
Q

Acepromazine - indications

A

Calming, potentiate other drugs, smooth induction/recovery

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20
Q

Acepromazine - effects

A

Tranquilization and vascular relaxation

- slow onset, long duration

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21
Q

Acepromazine pros

A
  • smooth recovery
  • minimal respiratory depression
  • combine with opioids for neuroleptanalgesia
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22
Q

Acepromazine is contraindicated in _______

A

Hypovolemic shock

  • antagonism of peripheral alpha-1 receptor activity
  • prevents vasoconstrictive response to shock
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23
Q

Acepromazine - side effects

A

Potential for hypotension

  • penile prolapse in horses
  • slow heart rate in boxers
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24
Q

Trazodone

A

Serotonin antagonist reuptake inhibitor

  • potent antagonism of serotonin 2A receptors, weak inhibition of postsynaptic serotonin reuptake
  • used in humans as an antidepressant, anxiolytic, sleep aid, anti-obsessive agent
  • popular adjunct for long-term treatment of anxiety in dogs and short-term post-surgery anxiolysis
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25
Q

Benzodiazepines - mechanism

A

GABA agonists

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26
Q

Benzodiazepines - effects

A
  • decreased anxiety
  • euphoria/dysphoria!
  • muscle relaxation
  • anti-seizure activity
27
Q

Benzodiazepines - indications

A

Potentiate other agents for smoother induction and recovery

- decrease doses of other agents

28
Q

Benzodiazepines - side effects

A
  • wide individual/species variation
  • not great when used alone (euphoria)
  • mild respiratory depression
  • minimal CV effects
  • antagonist (flumazenil)
  • controlled substance (class 4)
29
Q

Midazolam

A

Versed

- water soluble, suitable for IM, SQ intranasal, rectal

30
Q

Diazepam

A

Valium

  • propylene glycol carrier
  • IV only
31
Q

Alpha 2 adrenergic agonists

A

Dose-dependent analgesia and sedation

  • analgesia –> direct activation of spinal A2 dorsal horn receptors
  • sedation –> noradrenergic A2 receptors in brainstem
  • vagomimetic
  • peripheral vasoconstriction
32
Q

Where are alpha-2 receptors found?

A

Everywhere!

  • brain
  • spinal cord
  • GIT
  • pancreas
  • uterus
  • blood vessels
33
Q

Alpha-2 agonists - effects

A
  • sedation
  • analgesia
  • relaxation
  • CV and respiratory depression
  • vasoconstriction
  • hyper, then hypotension
  • diuresis
  • hyperglycemia
  • vomiting
34
Q

Alpha-2 agonists - indications

A

Combined with other agents for short-term anesthesia or chemical restraint

  • sedation/analgesia
  • anesthetic premedication
35
Q

Alpha-2 agonists - pros

A
  • excellent analgesia
  • sedation, NOT anesthesia!
  • not DEA controlled
  • antagonists are available
36
Q

Alpha-2 agonists - side effects

A
  • vomiting in small animals
  • small animals may bite
  • horses may kick
  • ruminants: very sensitive (use lower dose)
  • swine: very insensitive
37
Q

Alpha-2 agonists as an abortigenic

A

Only xylazine in cattle

  • 3rd trimester
  • profound CV and respiratory depression
  • bradycardia and secondary AV block
  • vasoconstriction
38
Q

Xylazine, detomidine, dexmedetomidine, romifidine are all ______

A

Alpha-2 agonists

39
Q

Xylazine

A

Commonly used

  • large and small animals
  • most popular restraint drug in horses and ruminants
40
Q

Dexmedetomidine

A

150x more potent than xylazine

  • approved only for healthy dogs
  • profound sedative effects
  • with ketamine for injectable anesthesia
41
Q

Detomidine and romifidine

A

Used in horses

  • longer lasting than xylazine
  • more potent (use less)
42
Q

Which drugs reverse all effects of alpha-2 agonists?

A

Yohimbine, tolazoline, atipamezole

- causes hypertension, tachycardia

43
Q

Opioids - mechanism

A

Inhibition of nociceptive information pathways

44
Q

Opioids - effects

A

Analgesia, respiratory depression (increase CO2), bradycardia, sedation (dogs, primates), euphoria (cats, horses), vomiting

45
Q

Opioids - indications

A

Analgesia, sedation, potentiate other agents, smooth induction and recovery

46
Q

Opioids - pros

A
  • minimal CV effects
  • wide margin of safety
  • useful in most species
  • antagonists are available
47
Q

Opioids - species indications

A
  • sedation: dogs, primates
  • analgesia
  • excitation: likely in cats, horses at doses higher than used clinically
48
Q

Opioids - side effects

A
  • dose dependent respiratory depression
  • bradycardia
  • vomiting
  • euphoria, dysphoria
  • dogs pant excessively
  • most are DEA scheduled
49
Q

Classes of opioids

A
  • full agonists
  • partial agonists
  • kappa agonists/mu antagonists
  • antagonists
50
Q

Full (mu) agonists

A
  • morphine
  • hydromorphone
  • oxymorphone
  • fentanyl
  • methadone
  • buprenorphine (partial)
51
Q

Kappa agonist/mu antagonist

A
  • butorphanol

- nalbuphine

52
Q

Butorphanol

A
  • short duration (45-60 min)
  • minimal to moderate analgesia –> poor choice for post op pain control
  • minimal sedation
  • expensive
  • DEA class 4
53
Q

Naloxone

A

Opioid antagonist

  • reverses ALL opioid effects
  • can cause tachycardia, hypertension, pulmonary edema
  • short duration of action
54
Q

Naltrexone

A

Potent, long lasting opioid antagonist

- used in zoo and wild animal practice

55
Q

Neuroleptanalgesics

A

Opioid and tranquilizer or sedative –> greater sedation and analgesia

  • numerous combinations
  • reduce dose requirements
56
Q

Neuroleptanalgesia

A

Consider instead of single drugs

  • fewer adverse effects, better restraint
  • combo of tranquilizer or sedative and analgesic drug to achieve heavy sedation and analgesia
57
Q

Dissociative anesthetics - mechanism

A

Interference with transmission between conscious and subconscious areas of brain

  • antagonism of excitatory amino acid neurotransmitters
  • N-methyl-D-aspartate, glutamate
58
Q

Dissociative anesthesia - effects

A

Interruption of neurotransmission between thalamocortical and limbic areas

  • muscle tone and eye reflexes remain
  • ketamine, telazol
  • maintenance of some motor, most autonomic tone
59
Q

Dissociatives - indications

A

Chemical restraint or injectable anesthesia

60
Q

Dissociatives - side effects

A
  • poor muscle relaxation
  • sympathomimetic actions (increase hr)
  • poor recovery quality
  • respiratory depression
  • renal excretion in cats (dont give to renal failure patients!!)
  • hepatic and renal in other species
61
Q

Ketamine

A

Widely used

  • wide margin of safety
  • use in almost any animal species
  • best in combos with tranquilizer, opioid, alpha-2 agonist
  • DEA class 3
62
Q

Telazol

A

Dissociative plus benzodiazepine

  • tiletamine/zolazepam
  • more potent than ketamine –> use less
  • DEA class 3
63
Q

Other premed drugs

A
  • NSAIDS
  • antihistamines
  • neurosteroids
64
Q

Aflaxan

A

Modulates GABA receptors

- chemically identical to progesterone, modified to not produce sex or glucocorticoid effects

Intro to Anesthesiology (10 decks)

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