Preanesthetic Medications Flashcards
(64 cards)
1
Q
Many drugs are _____
A
Receptor mediated
- either agonists or antagonists
2
Q
Most drugs that produce CNS depression are either _____ at inhibitory sites, or ____ at excitatory sites
A
Agonists; antagonists
3
Q
Desired effect of most anesthetic type drugs
A
CNS
- few drugs are 100% selective
- most have adverse effects
4
Q
Premeds
A
Drugs given before induction of anesthesia
- individual drugs are rarely ideal
- combinations are common
5
Q
Indications
A
- calm, sedate, chemical restraint
- analgesia
- decrease drug requirements
- offset adverse drug effects
- smooth induction/recovery
6
Q
Factors in choosing premeds
A
- temperament
- desired effects
- undesirable drug effects
- pain involved
- health status
- type of practice
- personal preferences
7
Q
Classes of drugs
A
- anticholinergics
- tranquilizers
- alpha-2-adrenergic agonists
- opioids
- neuroleptanalgesics
- dissociatives
8
Q
Anticholinergic - mechanism
A
Competitive antagonism of AcH at parasympathetic muscarinic cholinergic receptors
9
Q
Anticholinergic - effects
A
- increased heart rate
- decreased secretions
- decreased GI motility
10
Q
Anticholinergic - indications
A
- prevent or treat vagally mediated bradycardia
- decrease salivary and/or respiratory secretions
11
Q
Atropine and glycopyrrolate are ______
A
Anticholinergic agents
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
13
Q
Atropine cannot be used in _________
A
Ruminants or rabbits due to rapid hydrolyzation
14
Q
Glycopyrrolate
A
Does not cross BBB or placenta
- duration 2-4 hrs
- less tachycardia
- less effective
- more expensive
15
Q
Avoid anticholinergic agents in:
A
- ruminants and horses due to effect on GI motility
- animals with tachyarrhythmias
- questionable in routine cases
16
Q
Anticholinergic are parasymptholitic
A
Can’t use heartrate as an indicator of anesthetic depth
17
Q
Tranquilizers
A
- do produce calming
- do not provide chemical restraint
- do not provide analgesia
18
Q
Acepromazine - mechanisms
A
Central antagonism of D2 dopamine receptors and H1 histamine receptors
- peripheral alpha-1 adrenergic blockade
19
Q
Acepromazine - indications
A
Calming, potentiate other drugs, smooth induction/recovery
20
Q
Acepromazine - effects
A
Tranquilization and vascular relaxation
- slow onset, long duration
21
Q
Acepromazine pros
A
- smooth recovery
- minimal respiratory depression
- combine with opioids for neuroleptanalgesia
22
Q
Acepromazine is contraindicated in _______
A
Hypovolemic shock
- antagonism of peripheral alpha-1 receptor activity
- prevents vasoconstrictive response to shock
23
Q
Acepromazine - side effects
A
Potential for hypotension
- penile prolapse in horses
- slow heart rate in boxers
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
25
Benzodiazepines - mechanism
GABA agonists
26
Benzodiazepines - effects
- decreased anxiety
- euphoria/dysphoria!
- muscle relaxation
- anti-seizure activity
27
Benzodiazepines - indications
Potentiate other agents for smoother induction and recovery
| - decrease doses of other agents
28
Benzodiazepines - side effects
- wide individual/species variation
- not great when used alone (euphoria)
- mild respiratory depression
- minimal CV effects
- antagonist (flumazenil)
- controlled substance (class 4)
29
Midazolam
Versed
| - water soluble, suitable for IM, SQ intranasal, rectal
30
Diazepam
Valium
- propylene glycol carrier
- IV only
31
Alpha 2 adrenergic agonists
Dose-dependent analgesia and sedation
- analgesia --> direct activation of spinal A2 dorsal horn receptors
- sedation --> noradrenergic A2 receptors in brainstem
- vagomimetic
- peripheral vasoconstriction
32
Where are alpha-2 receptors found?
Everywhere!
- brain
- spinal cord
- GIT
- pancreas
- uterus
- blood vessels
33
Alpha-2 agonists - effects
- sedation
- analgesia
- relaxation
- CV and respiratory depression
- vasoconstriction
- hyper, then hypotension
- diuresis
- hyperglycemia
- vomiting
34
Alpha-2 agonists - indications
Combined with other agents for short-term anesthesia or chemical restraint
- sedation/analgesia
- anesthetic premedication
35
Alpha-2 agonists - pros
- excellent analgesia
- sedation, NOT anesthesia!
- not DEA controlled
- antagonists are available
36
Alpha-2 agonists - side effects
- vomiting in small animals
- small animals may bite
- horses may kick
- ruminants: very sensitive (use lower dose)
- swine: very insensitive
37
Alpha-2 agonists as an abortigenic
Only xylazine in cattle
- 3rd trimester
- profound CV and respiratory depression
- bradycardia and secondary AV block
- vasoconstriction
38
Xylazine, detomidine, dexmedetomidine, romifidine are all ______
Alpha-2 agonists
39
Xylazine
Commonly used
- large and small animals
- most popular restraint drug in horses and ruminants
40
Dexmedetomidine
150x more potent than xylazine
- approved only for healthy dogs
- profound sedative effects
- with ketamine for injectable anesthesia
41
Detomidine and romifidine
Used in horses
- longer lasting than xylazine
- more potent (use less)
42
Which drugs reverse all effects of alpha-2 agonists?
Yohimbine, tolazoline, atipamezole
| - causes hypertension, tachycardia
43
Opioids - mechanism
Inhibition of nociceptive information pathways
44
Opioids - effects
Analgesia, respiratory depression (increase CO2), bradycardia, sedation (dogs, primates), euphoria (cats, horses), vomiting
45
Opioids - indications
Analgesia, sedation, potentiate other agents, smooth induction and recovery
46
Opioids - pros
- minimal CV effects
- wide margin of safety
- useful in most species
- antagonists are available
47
Opioids - species indications
- sedation: dogs, primates
- analgesia
- excitation: likely in cats, horses at doses higher than used clinically
48
Opioids - side effects
- dose dependent respiratory depression
- bradycardia
- vomiting
- euphoria, dysphoria
- dogs pant excessively
- most are DEA scheduled
49
Classes of opioids
- full agonists
- partial agonists
- kappa agonists/mu antagonists
- antagonists
50
Full (mu) agonists
- morphine
- hydromorphone
- oxymorphone
- fentanyl
- methadone
- buprenorphine (partial)
51
Kappa agonist/mu antagonist
- butorphanol
| - nalbuphine
52
Butorphanol
- short duration (45-60 min)
- minimal to moderate analgesia --> poor choice for post op pain control
- minimal sedation
- expensive
- DEA class 4
53
Naloxone
Opioid antagonist
- reverses ALL opioid effects
- can cause tachycardia, hypertension, pulmonary edema
- short duration of action
54
Naltrexone
Potent, long lasting opioid antagonist
| - used in zoo and wild animal practice
55
Neuroleptanalgesics
Opioid and tranquilizer or sedative --> greater sedation and analgesia
- numerous combinations
- reduce dose requirements
56
Neuroleptanalgesia
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
Dissociative anesthetics - mechanism
Interference with transmission between conscious and subconscious areas of brain
- antagonism of excitatory amino acid neurotransmitters
- N-methyl-D-aspartate, glutamate
58
Dissociative anesthesia - effects
Interruption of neurotransmission between thalamocortical and limbic areas
- muscle tone and eye reflexes remain
- ketamine, telazol
- maintenance of some motor, most autonomic tone
59
Dissociatives - indications
Chemical restraint or injectable anesthesia
60
Dissociatives - side effects
- 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
Ketamine
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
Telazol
Dissociative plus benzodiazepine
- tiletamine/zolazepam
- more potent than ketamine --> use less
- DEA class 3
63
Other premed drugs
- NSAIDS
- antihistamines
- neurosteroids
64
Aflaxan
Modulates GABA receptors
| - chemically identical to progesterone, modified to not produce sex or glucocorticoid effects
