7/8: Preanesthetic Meds Flashcards
1
Q
What are advantages of using anticholinergics as part of pre-anesthetic meds?
A
Prevention of salivation, airway secretions, bradycardia
2
Q
What are advantages of using maropitant as a pre-anesthetic med?
A
Prevention of nausea and vomiting;
It also provides adjuct analgesia (NK-1 antagonist) and decreases inhalant requirements
3
Q
What are 5 general advantages to using pre-anesthetic meds?
A
- Chemical restraint
- Decreased stress/anxiety –> decreased catecholamines –> decreased risk of arrhythmias
- Decreased induction and inhalant anesthetic doses
- Pre-emptive analgesia
- Smooth recovery
4
Q
What is pre-emptive analgesia?
A
Treatment initiated before surgery in order to prevent the establishment of central sensitization evoked by incisional and inflammatory injuries occurring during surgery and in the early post-op period.
5
Q
What are 4 disadvantages to using pre-anesthetic meds?
A
- Bradycardia
- Hypotension
- Excitement/dysphoria
- Nausea/vomiting
6
Q
What pre-anesthetic med types cause bradycardia?
A
Alpha-2 agonsists, opioids
7
Q
What pre-anesthetic med types cause hypotension?
A
Acepromazine, alpha-2 agonists
8
Q
What pre-anesthetic med types cause excitement/dysphoria?
A
Opioids, benzos
9
Q
What pre-anesthetic med types cause nausea/vomiting?
A
Mu-agonist opioids, dexmedetomidine
10
Q
What are 6 factors to consider when selecting a pre-anesthetic medication?
A
- Species
- Health status of patient
- Pain (existing and expected)
- Temperament
- Duration of procedure
- Anticipated side effects of drugs administered
11
Q
What 4 drug types can be used as analgesics?
A
- Opioids
- Dissociatives
- NSAIDs
- Alpha-2 agonists, maropitant
12
Q
What 2 drugs can be used as anticholinergics?
A
- Atropine
- Glycopyrrolate
13
Q
What 3 drug types can be used as tranquilizers/sedatives (neuroleptics)?
A
- Phenothiazines
- Alpha-2 agonists
- Benzos
14
Q
What 3 categories of drugs are used for premeds?
A
Opioids, sedatives/tranquilizers, anticholinergics
15
Q
What 5 opioid drugs are pure mu agonists?
A
- Hydromorphone
- Fentanyl
- Morphine
- Methadone
- Oxymorphone
16
Q
What opioid drug is a mixed kappa agonist/mu antagonist?
A
butorphanol
17
Q
What opioid drug is a partial mu agonist?
A
Buprenorphine
18
Q
What opioid drugs are full mu antagonists?
A
Naloxone, naltrexone
19
Q
What are the 3 opioid receptors?
A
mu, kappa, delta
20
Q
Where are opioid receptors located?
A
In peripheral and central nervous systems
21
Q
What is the mechanism of action for opioids?
A
Opioid receptors are coupled with inhibitory G-proteins (GPCRs) which activate 2nd messenget systems in cells
22
Q
What are the 2nd messenger systems that are activated by G-proteins?
A
- Closing of Ca channels
- Efflux of K –> hyperpolarization
- Decreased cAMP production
23
Q
What are 4 overall results that opioids have on cells?
A
- Hyperpolarization
- Decreased neuronal excitability
- Decreased neurotransmitter release
- Decreased transmission of nerve impulses
24
Q
Naxolone is such a weak mu _____ that we consider it an _____.
A
agonist, antagonist
25
Effects of mu/kappa agonists are _____ dependent, and there is no _____ effect.
dose, ceiling
26
What are some clinical side effects cause by mu agonists?
1. Analgesia
2. Inhalant sparing
3. Mild to profound sedation
4. Bradycardia
5. Respiratory depression
6. GI: nausea, vomiting, decreased motility
7. Urinary retention
8. Hyperthermia in cats
27
What does it mean if a drug has a ceiling effect?
Increased dose does not = increased analgesia
28
What 2 opioid types have a ceiling effect?
Partial mu agonists (Buprenorphine)
K agonist/mu antagonist (Butorphanol)
29
What can Butorphanol be used with?
Dexmedetomidine
30
What type of analgesia do opioids provide?
Somatic and visceral
31
When do opioids provide mild sedation?
When used alone
32
What mild CV effects do opioids have?
1. Decreased HR due to increased vagal tone --\> anticholinergic
2. Little/no effect on vasculature (histamine release)
3. Little/no effect on cardiac contractility
33
Opioids _____ the MAC of inhalant.
decrease
34
When should you use full mu agonists?
With moderate to severe pain
35
What is the duration of action of hydro/oxymorphone?
2-4 hours
36
What is the duration of action of morphine/methadone?
4-6 hours
37
Methadone is an NMDA \_\_\_\_\_.
antagonist
38
What effects can morphine have on vasculature?
Histamine release
39
A side effect of full mu agonists is ______ to ______ analgesia.
moderate, severe
40
What is a CV side effect that mu agonists cause?
bradycardia
41
What GI side effects do mu agonists cause?
Nausea, vomiting, defecation
42
What do mu agonists cause in cats specifically? (side effect)
hyperthermia
43
What can you give together with hydromorphone to mitigate the side effects?
fentanyl
44
What type of drug is fentanyl?
pure mu agonist
45
What is the duration of fentanyl?
15-30 min
46
What is done to mitigate the short duration of fentanyl?
Given IV as a CRI
47
What is a CV side effect of fentanyl?
Bradycardia (\> other mu agonists)
48
What are GI side effects of fentanyl?
No vomiting; may cause nausea
49
Fentanyl can cause respiratory \_\_\_\_\_.
depression
50
What should be monitored intra-op when fentanyl is on board?
EtCO2, IPPV
51
What should be monitored post-op when fentanyl is on board?
SpO2
52
What are 3 ways that we use fentanyl?
1. Induction agent in critically ill SA patients
2. Intra-op and post-op CRI
3. Patch (post-op)
53
Buprenorphine produces _____ sedation, and _____ to _____ analgesia.
mild, mild, moderate
54
What is the onset of buprenorphine?
30-45 min (slow)
55
What is the duration of buprenorphine in dogs and cats?
Dogs = 4-10 hours
Cats = 6-12 hours
56
Buprenorphine has a strong _____ for the mu receptor.
affinity
57
When should you not use buprenorphine as a pre-med?
If the procedure is painful
58
What is a disadvantage of buprenorphine?
It is difficult to reverse
59
What is the SA dose of buprenorphine?
0.01 - 0.04 mg/kg
60
How does buprenorphine compare to mu agonists?
It has LESS:
1. Respiratory depression
2. Panting
3. Bradycardia
4. Analgesia, MAC sparing
5. No nausea, vomiting
61
What is the new, long acting formulation of buprenorphine approved for cats?
Simbadol - 0.24 mg/kg SQ SID
62
Because butorphanol is a mu antagonist, it is a partial _____ \_\_\_\_\_.
reversal agent
63
Butorphanol provides _____ sedation and analgesia.
mild
64
How long does sedation with butorphanol last? Analgesia?
Sedation = 1-2 hours
Analgesia = ~90 min
65
How does butorphanol compare to mu agonists?
It has LESS:
1. Respiratory depression
2. Panting (seen at higher doses)
3. Bradycardia
4. Analgesia, MAC sparing
5. No nausea/vomiting
66
What does butorphanol prevent that dexmedetomidine causes?
nausea/vomiting
67
What type of procedure should butorphanol be used for?
Sedation for non-painful procedures (i.e. x-rays)
68
How is butorphanol used in dogs and cats?
Alone (dogs) or with sedative/tranquilizer
69
What is the dose for butorphanol?
0.2 - 0.4 mg/kg
70
How should butorphanol be used in horses?
With alpha-2 agonist for pre-med/intra-op
71
How should butorphanol be used in large ruminants? Small ruminants?
Large = during/after induction (vocalization)
Small = as premed + benzodiazepine
72
What are the 4 sedatives/tranquilizers used?
1. Acepromazine
2. Alpha-2 agonists
3. Benzodiazepines
4. Dissociatives - not sedatives but used for chemical restraint
73
What is an alpha-2 agonist used in SA?
Dexmedetomidine
74
What are 3 alpha-2 agonists used in LA (primarily horses)?
1. Xylazine
2. Detomidine
3. Romifidine
75
What are 2 common benzodiazepines used?
Midazolam and Diazepam
76
What are 2 dissociatives used for chemical restraint?
1. Ketamine
2. Tiletamine (in Telazol)
77
What type of drug is acepromazine?
Phenothiazine
78
What does acepromazine do cellularly?
Blocks dopamine, 5-HT, and alpha-1 adrenergic receptors
79
What anatomical locations does acepromazine act on?
Basal ganglia, hypothalamus, limbic system, brain stem, reticular activating system (RAS)
80
Why is acepromazine an effective tranquilizer?
It blocks D and 5-HT Rs --\> depression of brain stem and RAS connections to cerebral cortex
81
How does acepromazine affect the vessels?
Causes vasodilation through an alpha-1 adrenergic blockade
82
What CV effects does acepromazine have?
1. Decreased symp tone (sinus bradycardia, 2nd deg AV block)
2. "Anti-arrhythmic" effect - cardiprotectant
83
What respiratory effect does acepromazine have?
resp depression
84
Ace _____ nausea/vomiting through ___ receptors in the chemoreceptor trigger zone.
decreases, D
85
What effect does ace have on PCV?
Decreased due to splenic sequestration
86
What effect does ace have on platelets?
Altered plt function
87
What effect does ace have on body temp?
Hypothermia (peripheral vasodilation or effects on hypothalamus, redist of blood from core to periphery)
88
Ace does not have _____ effects BUT has synergistic effects with \_\_\_\_\_.
analgesic, opioids
89
Ace _____ induction dose and MAC of inhalant.
decreases
90
Ace produces _____ to _____ sedation.
mild, moderate
91
What is the onset of action of ace?
~20-30 min
92
What is the duration of ace?
4-6 hours
93
T/F: Ace has a reversal agent
False
94
Where is ace metabolized and excreted?
Metab in the liver, excreted by kidney
95
What can happen if ace is accidentally injected into the carotid in horses?
Seizures and death
96
Why should ace not be used for allergy testing?
Blocks histamine
97
What are 3 contraindications for ace use?
1. Moderate/severe liver dysfunction
2. Hypovolemia, shock, critically ill patients
3. Paraphimosis in stallions --\> relaxation of penis retractor muscle via alpha-1 blockade
98
What dogs cannot have ace?
Those with a mutation in the ABCB1/MDR1/P-gp gene (i.e collies)
99
How can ace be administered?
PO, SQ, IM, IV
100
What is the dosage for ace?
0.005 - 0.02 mg/kg IM or IV
101
What is the alpha-2 to alpha-1 receptor ratio?
1600:1
102
What are the 3 isoreceptors of alpha-2 drugs?
Alpha-2A, alpha-2B, alpha-2C
103
What type of receptor are alpha-2 receptors?
GPCR
104
Where is the alpha-2A receptor and what is its effect?
In locus ceruleus (brain) --\> inhibition --\> sedation, anxiolysis, sympatholytic properties
105
Where is the alpha-2B receptor and what is its effect?
In vasculature --\> excitatory --\> vasoconstriction
106
Where are therer both alpha-2B and 2C receptors and what is their effects?
Dorsal horn of spinal cord --\> inhibit nociception
107
What are the biphasic CV effects of alpha-2 agonists?
1. Initial hypertension (10-30 min) response due to peripheral alpha-2B stim with vasoconstriction
2. Central alpha-2A stim --\> decreased NE --\> hypotension due to bradycardia and peripheral vasodilation
108
In relation to alpha-2 agonists:
Initially, bradycardia is a _____ mediated response due to increased BP, while decreased _____ slows HR in latter phase.
baroreceptor, sympathetic outflow
109
What is the treatment for alpha-2 agonist induced bradycardia that has a normal to high BP and why?
No treatment necessary because anti-cholinergics will increase BP too much and can cause retinal hemorrhage and detachment.
110
What is the treatment for alpha-2 agonist induced bradycardia that has a low BP and why?
Treatment with anti-cholinergic indicated ~ 1 hour after administration due to central alpha-2A sympatholytic effect
111
What are 3 uses for dexmedetomidine?
1. Premed (dogs and cats)
2. Intra-op CRI (dogs, cats, horses)
3. Sedation for recovery (dogs and cats)
112
What is the dosage for dexmedetomidine as a premed?
5.0 - 10 mcg/kg
| (Lower end in dogs, higher end in cats)
113
What is the analgesic/sedative effect of dexmedetomidine?
potent and dose-dependent
114
What is the onset of dexmedetomidine?
Rapid (~5 min)
115
What is the duration of action of dexmedetomidine?
Short (~30-60 min, dep on dose)
116
What is the dosage for dexmedetomidine as an intra-op CRI?
1.0 - 2/0 mcg/kg/hr
117
What is the dosage for dexmedetomidine when used in sedation for recovery?
0.5 - 1.0 mcg/kg IV
118
What CV effects does dexmedetomidine have?
40% decrease in CO, reflex bradycardia due to vasoconstriction
(Can decrease chance of heart attack post-op in humans)
119
Can dexmedetomidine be reversed?
Yes - Atipamazole (Antisedan®)
120
What type of patient should dexmedetomidine be reserved for?
Healthy or very painful, fearful, aggressive patients
121
What can be added to dexmedetomidine if the patient is unhandleable after administration?
Ketamine 1.0 - 2.0 mg/kg
122
What alpha-2 agonists can be used in horses? What are the reversals?
Xylazine, Detomidine, Romifidine;
Reversals = yohimbine, tolazoline
123
What is the cellular effect/method of action of Benzodiazepines?
Enhance effect of ntm GABA at the GABAA receptor --\> increase Cl into cell --\> hyperpolarization
124
What can benzodiazepines be used for, generally?
Sedation, hypnosis, anxiolysis, amnesia, anticonvulsant, muscle relaxant
125
What are 2 benzodiazepines that are commonly used?
Diazepam and Midazolam
126
Diazepam and midazolam typically are NOT good _____ in young, healthy dogs and cats. What can they be used for?
sedatives;
Diazepam = tx of seizures
Midazolam = premed
127
What do Diazepam and Midazolam do that we do not want to happen?
Cause paradoxical excitement, hyperresponsiveness
128
What animals experience more profound sedation with BDZ?
Pediatric (\<3 mos), geriatric, critical, small ruminants, neonatal foals
129
What is the severity of CV effects of BDZ?
mild
130
What is the respiratory effect of BDZ?
Enhances resp depression of other drugs
131
Where are BDZ metabolized?
Liver - both have active metabolites
132
What is the 1/2 life of diazepam in dogs? Cats? Horses?
Dogs = 2-4 hours
Cats = 5.5 hours
Horses = 7-22 hours
133
What is the 1/2 life of midazolam in dogs? horses?
Dogs = ~70 min
Horses = ~3-6 hours
134
What do BDZ NOT provide?
analgesia
135
What does diazepam contain that can cause issues?
Propylene glycol;
Pain on injection, not well absorbed, toxic at high doses
136
What is the relative cost of midazolam and diazepam?
Relatively similar
137
What do we use midazolam with in dogs and cats?
With an opioid for premed in very young, geriatric, or sick patients
138
What is the dosage for midazolam in dogs and cats?
0.1 - 0.2 mg/kg IM or IV
139
What induction agent dose can be reduced if midazolam is used as an adjunct with it in dogs and cats?
propofol
140
What drug is midazolam used as a co-induction agent with in adult horses?
ketamine
141
What drug is midazolam used as a co-induction agent with in neonate horses?
Butorphanol
142
What drug is midazolam used as a co-induction agent with in small ruminants?
Ketamine or Propofol
143
What is the method of action of anti-cholinergics?
Antagonize ACh at muscarinic Rs at post-ganglionic sites in parasympathetic nervous system (increases sympathetic tone)
144
What do anti-cholinergics do to vagal effects and salivary secretions?
Decreases them
145
What are anti-cholinergics primarily used for?
To counter vagal effects of anesthetic drugs
146
What are the 2 most common anti-cholinergics?
Atropine and Glycopyrrolate
147
What effect do anti-cholinergics have on the heart rate?
Increases it
148
What effect do anti-cholinergics have on salivation?
Decreases it
149
What effect do anti-cholinergics have on mucociliary transport/clearance?
Decreases it
150
What effect do anti-cholinergics have on the pupils?
Dilates them (atropine)
151
What effect do anti-cholinergics have on GI motility in LA?
Decreases it; relaxation of gastro-esophageal sphincter
152
What effect do anti-cholinergics have on blood flow?
Decreases it --\> myocardial ischemia/hypoxemia
153
What heart conditions can anti-cholinergics be used to treat?
Sinus bradycardia, 1st and 2nd deg AV block, sinus arrest, CPCR
154
What is the onset of action of atropine?
\<5 min IM
\<1 min IV
155
What is the duration of action of atropine?
~30 min IV
156
What is atropine capable of crossing?
BBB/placenta;
Reason some people don't like to use it in C-sections
157
What is atropine more likely to cause than glycopyrrolate?
Sinus tachycardia
158
T/F: Glycopyrrolate crosses BBB/placenta
False
159
What is the onset of action of glycopyrrolate?
3-5 min
160
What is the duration of action of glycopyrrolate?
2-4 hours
161
Why should glycopyrrolate be avoided in LA?
GI stasis
162
What are 2 approaches for use of anti-cholinergics in SA?
1. Pre-treatment (expense, risk of tachycardia)
2. Treat if needed (monitor HR, rhythm, BP)
163
What 4 cautions should be taken when considering an anti-cholinergic?
1. LA
2. Geriatric patients or those with heart disease
3. Patients with low HR/high BP (dexmedetomidine)
4. Ineffective in patients with moderate/severe hypothermia
164
What are 3 considerations for an individualized anesthesia and analgesia plan that includes a preanesthetic?
1. **Opioid Analgesic** - butorphanol, buprenorphine, full mu agonist (or fentanyl IV)
1. Based on spp, pain, inhalant sparing needs, cost, availability
2. **Tranq/Sedative** - acepromazine, alpha-2 agonist, BDZ, GG
1. Based on signalment, temperament, physical status, co-morbidities
3. **+/- Anti-cholinergic**
