LEC 8,9 - General + Local Anesthetics Flashcards
1
Q
General anesthetic effects (5)
A
Analgesia
Loss of conciousness
Amnesia
Inhibition of snesory + ANS reflexes
Muscle relaxation
2
Q
Drugs for analgesia (2)
A
N2O
Opiods
3
Q
Drugs for loss of conciousness (2)
A
IV anesthetics
N2O
4
Q
Drugs for amensia (3)
A
Midazolam
Droperidol
Ketamine
5
Q
Drugs for ANS inhibition (3)
A
Atropine
Opiates
Scopolamine
6
Q
Drugs for muscle relaxation
A
Depolarizing + Nondepolarizing muscle relaxants
7
Q
What is the purpose of pre-medications?
A
Facilitate anesthesia + surgery
improves rapidity + smoothness of:
Iduction
Anxiety
Analgesia/Amnesia
8
Q
What are the four major drug groups used for pre-meds?
A
Opiods
tranquilizers
Anticholinergics
Central muscle relaxants
9
Q
What is the purpose of opioids in pre-meds?
A
Analgesia
10
Q
What is the purpose of tranquilizers in pre-meds?
A
Pre-operative sedation + amnesia
Prevent/counteract CNS stimulation
11
Q
What is the purpose of anticholinergics in pre-meds?
A
Prevent salivation + bradycardia
12
Q
Propofol - Mechanism
A
Activates GABAa receptors
13
Q
Propofol - admin
A
IV
14
Q
Propofol - Distribution
A
Rapid redistribution + metaboolism
15
Q
Propofol - Effects on cerebral pressure
A
Decreases blood flow + oxygen consumption
Safe for animals with head trauma
16
Q
Propofol - Duration of anesthesia
A
2 to 10 min
17
Q
Propofol - Distribution/breeds to watch out for
A
Distributes to fat
Sighthounds
18
Q
Propofol - Metabolism
A
Glucoronidation
19
Q
Propofol - 1/2 life
A
1 to 2 hours
20
Q
Propofol - Adverse effects
A
Myoclonic twitching
Myocardial depression
Transient apnea
21
Q
Etomidate - Mechanism
A
Sedative hypnotic nonbarbiturate
Facilitates GABA transmission
22
Q
Etomidate - Effects
A
Decrease cerebral blood flow
Metabolic rate
oxygen consumption
23
Q
Etomidate - Uses
A
Good for patients with:
Cardiac dysfuncton
Head trauma
Critically ill
24
Q
Etomidate - Metabolism
A
Heptaic hydrolysis
No accumulation
25
Etomidate - 1/2 life
3 hours
26
Etomidate - Adverse effects
Very hypertonic
Pain + Hemolyssi upon IV injection
27
Alfaxalone - Mechanism
Synthetic neuroactive steroid
Interacts with GABA receptors
Anesthesia + Muscle relaxtion
28
Alfaxalone - 1/2 life
\< 1 hour
29
Alfaxalone - Pharmacokinetic curce
non-linear aka zero order
30
Alfaxalone - Use
General anesthesia
Bolus or CRI
31
Alfaxalone - Adverse effects
CNS depression
Hypotension
32
Ketamine - Use
FDA approval in cats
Induction
CRI for general anestehsia
Sedation for chemical restraint
33
Ketamine - Mechanism
Inhibits excitaory NT ACh + L-glutamate in spinal cord
Non-competitive antagonist of NNMDA receptor
Dissociative anesthesia
Analgesia
34
Ketamine - Admin
IM/IV - Cats + Dogs + Small Ruminants + Swine
IV - Adult horses
35
Ketamine - Metabolism
CYP450
Congugated with glucuronide
36
Ketamine - Excretion
Kidneys -
Unchanged in cats
37
Ketamine - 1/2 life
Cat
Calf
Horse
= 1 to 1.5 hours
38
Ketamine - Adverse side effects
Seizures (Horses + Dogs )
Profuse salivation (Cats)
SNS stimulation = Inc CO + HR
Rougher induction/recovery
Increase muscle tone
Apneustic breathing pattern
CSF pressure increased
39
What muscle relaxers are given with ketamine?
Alpha2 agonists - to horses for muscle relaxation
Diazepam/Midazolam/etx. - to cats/dogs for seizure prevention + skeletal muscle relaxation
40
Midazolam - Mechanism
Benzodiazapine
Increases effects of GABA
Increases frequency of open Cl- channel
41
Midazolam - Use
Induction
Neonatal seizures
Status epilepticus
42
Midazolam - Neuroleptanalgesic combo
+ Opioid
43
Midazolam - Muscle relaxation combo
Ketamine
44
Midazolam - Protein bidning
94 to 97% bound
Unbound crosses BBB to enter CSF
45
Midazolam - Admin
SC + IM + IV
46
Midazolam - metabolism
Glucuronidation in liver
47
Midazolam - Affinity vs. Potency
2x's affinity for GABA
3x's potency
48
Midazolam - Adverse effects
Cardiorespiratory depression
Paradoxical excitement
Dysphoria
w/ drugs that have protein binding will increase CSF concentration
49
Midazolam - reversal
Flumazenil
50
Flumazenil - Mechanism
Competitive antagonist for BZD receptors
51
Tiletamine/Zolazepam - Use
Chemical resitrant in fracitous cats
Short term anesthesia in dogs/cats
52
Tiletamine/Zolazepam - Admin
Deep IM
53
Tiletamine/Zolazepam - Adverse effects
Excessive salivation
Erratic recovery
Muscle twitching
54
How do you treat excessive salivation with Tiletamine/Zolazepam administration?
Atropine
55
Barbiturates - Mechanism
Bind to GABA Cl- channels
Increase duration of opening
= hyperpolarization of neurons
56
Barbiturates - effects
Transient hypotension + increased HR
Depress respiratory centers (Cats \> Dogs)
General anesthesia
57
Barbiturates - overdose
Apnea
Cardiovascular depression
Death
58
Barbiturates - Distribution factors
Lipid solubility
Protein binding
Ionization
59
What type of drugs cross the BBB?
Non-protein bound
-- and --
Non-ionized
60
Why are thiobarbiturates rapid in onset?
High lipid solubiltiy
61
Characteristics of ultrashort acting barbiturates
very lipid soluble
Onset rapid
Duration short (10 to 30min)
62
Methohexital - use
Dogs/Cats
Ultra short procesures
63
Methohexital - Duration of action
5 to 15 minutes
64
Methohexital - Time of onset
15 to 60 seconds
65
Methohexital - Distribution
No effect on fetus so safer for C-section
Can reduce O2 in pups so move fast
Does not move to fat - good in greyhounds
66
Methohexital - Adverse effects
More likely to cause period of excitement during induction
Profound respiratory depression
67
Pentobarbital - Four main uses
Sedation
General anesthesia
Seizure control
Euth
68
Pentobarbital - Sedation uses
Mechanical ventilation
Ruminants + Horses
69
Pentobarbital - General Anesthetic uses
Cats/Dogs
70
Pentobarbital - Seizure uses
Refractory to phenobarbital or diazepam
71
Pentobarbital - duration of action
30 to 60 min
72
Pentobarbital - 1/2 life
Ruminants - 0.9 hours
Dogs - 8 hours
73
Pentobarbital - Adverse effects
Low doses - ecitement phase
74
Phenobarbital - mechanism
Long-acting
75
Phenobarbital - uses
Anticonvulsant in status epilepticus treatment
Excess, chronic drooling in dogs
Chlorinated hydrocarbon detox in cattle
76
Phenobarbital - ADmin
PO
IV loading in horses
77
Phenobarbital - Duration of action
6 to 12 hours
78
Phenobarbital - Metabolism
Liver 75 %
Urine, unchanged 25%
79
Phenobarbital - Adverse effects
Ataxia + Lethargy + depression
PU/PD/PP
Coagulopathies + Adrenal insufficency in cats
Increased liver enzymes in dogs
80
Define: MAC
1 mac = [] at 1 atm that prevents skeletal muscle movemnet in painful stim in 50% of the population
81
Oil : Gas ppartition coefficients
Measure of potency
82
MAC-awake
Inhibits voluntary movements
83
MAC-BAR
Blunting autonomic reflexs
84
MIR
Eliminates reflexes used to judge depth of anestehisa
85
Blood : Gas Partition Coeffcient
Rate of increase of Pa towards Pi
Inversely related to solubility of anesthetic to blood
86
Partition coefficient =
Solubility of inhaled anesthetic in different body components
87
Nitrous Oxide - Effects
Direct myocradial function depression
SNS stimulation
No sensitization of myocardium to epi
88
Nitrous Oxide - Use
Not very potant
Combine with other inhaled anesthetics to make more stable anesthesia
Analgesic
89
Nitrous Oxide - Secondary effects
Second gas effect
Diffusional hypozia
90
Describe second gas effect
Nitrous + Other inhalant anesthetic
NO highly diffusible, quick to leave alveoli
[] of other compoundss increase in alveoli
[] effect increases theri absorption into the blood
= decrease concentration needed
91
Nitrous Oxide - Distribution
Accumulations in gas filled spaces
Rumen of cattle
Cecum of horses
92
Describe diffusion hypoxia
NO is turned off
NO quickly diffuses out of blood into alveoli
Intra-alveolar oxygen [] is decreased
93
Treatment for diffusion hypoxia
100% oxygen
94
Preventing diffusion hypoxia
Wean patients off of NO
95
Isoflurane - Effects
Decrease arterial BP
Depresses CV function
Catecholamine sensitization = Cardiac arrhythmias
RR + TV decreased
Increases effect of non-depolarizing muscle relaxers
96
Isoflurane - MAC that effects cerebral blood floow
1.2
97
Isoflurane - Use
Dog + Cats + Birds + Horses
Anesthetic
Status epilepticus in Dogs (refractory to benzodiazepines)
98
Isoflurane - kinetics
Low blood : gas partition coeffiecent
Rapid induction/recovery
Exhaled unmetabolized
99
Isoflurane - Adverse effects
Malignant hyperthermia
Higher risk of causing vasodilation
(Responsive to fluid bolus)
100
Sevoflurane - Effects
Decrease SV
Depresses myocardial contractility
Decreases arterial BP
101
Sevoflurane - Kinetics
Low blood : Gas partition coefficient
Fast induction/recovery
102
Sevoflurane - Elimination
Liver - 2 to 5%
The rest is exhaled
103
Sevoflurane - Adverse effects
Malignant hyperthermia
104
What is the order in which euthanasia should take place?
Rapid loss of conciousness
Loss of motor function
Arrest of respiratory + cardiac functions
Permanent loss of brain function
105
Barbiturates for Euth - mechanism
Depress CNS in descending order
Cerebral cortex w/ loss of conciousness to anesthesia
Repsiratory center depression
Cardiac arrest
106
Barbiturates for Euth - Food animals
NEVER TO BE USED IN ANIMALS IN THE FOOD CHAIN
107
Dissociative agents + Alpha2 antagonist - use in euth
Can be given prior to the admin of euthanasia solutions to minimize animal distress + help with restraint + easier euthanasia for O
108
Acceptable euthanasia methods - Cats
IV barbiturates
Anesthetic OD
109
Acceptable euthanasia methods - Cattle
IV Barbiturates
110
Acceptable euthanasia methods - Dogs
IV barbiturates
Anesthetic OD
111
Acceptable euthanasia methods - Horse
IV barbiturates
112
Acceptable euthanasia methods - Poultry
Injected barbiturates
Anesthetic OD
113
Acceptable euthanasia methods - Swine
Injected barbiturates
114
What are the two types of local anesthetics?
Esters
-- and --
Amides
115
Characteristics of esters
Shorter duration
Increased toxicity
116
How does sterochemistry effect local anesthetics?
Potency
Clinical properties
117
What is the purpose of salts in local anesthetics?
Increase stability + solubility
118
pKa of local anesthetics
7.5 to 9
119
Predominant form of Local anesthetic in body
Ionized form LAH+
120
Where is the binding site for the local anesthetics?
Inner membrane
121
What is steps in which local anesthetics enter the cell?
Non-ionized cross membrane
Become ionized within the cell and become stuck
Ionized form binds within the cell
aka Hydrophobic pathway
122
Target of local anesthetics
Block Na+ channel = inhibit neuronal firing
123
effect of local anesthetics on the neuron
Increased t-hold for excitation
Slowed impulse conduction
124
What is the amount by which the local anesthetic blocks the area dependent on?
Voltage
Firing time
125
What channel type are local anesthetics have the highest affinity for?
Acitvated + inactivated
126
What neuronal activity level do local anesthetics have the highest affinity for?
Rapidly firing
127
Where are the adverse effects targeted with local anesthetics?
CNS + Cardiac
128
Duration of action dependent on =
Time at site
129
Toxic effects dependent on =
1/2 life
130
What effect does epi have on local anesthetics?
Decreased diffusion of the drug
Prolongs duration of action
Decreases systemic absorption
Decreases risk of systemic toxicity
131
Amides - Elimination
Metabolized by liver CYP450s
132
Amides - Toxicity
seen with -
Hepatic disease
Reduced hepatic blood flow
133
Local anesthetics - Secretion
Renal
134
Esters - Metabolism
Rapid metabolism by butyrylcholinesterase in plasma
135
What are the four major adverse effects with local anesthetics?
CNS
CV system
Methemoglobinemia
Tissue damage
136
Local Anesthetics - CNS adverse effects
Skeletal muscle twitching first sign
Tonic-clonic seizures normally first clinical sign
137
Local Anesthetics - MetHg adverse effect
Use of prilocaine + benzocaine in cats and rabbits
138
Local Anesthetics - Tissue damage
Neurotoxicity
Myotoxicity
139
Local Anesthetics - CV system adverse effects
Prolonged PR + QRS interval due to slowed impulse conduction
Hypotension
Decreased myocardial strength
140
Tetracaine - Use
Opthalmological
141
Tetracaine - Mechanism
Ester
142
Tetracaine - Onset of action
\> 10 mintues
143
Tetracaine - Duration of action
2 to 3 hours
144
Tetracaine - Adverse effects
Burning + Chemosis
Allergic reaction
Chornic use = keratitis
Supressed blink reflex
145
Lidocaine - use
Correct Vtach + SVT + PVT in dogs
Analgesia (Dogs +Horses)
Prokinetic effects (Horses)
146
Lidocaine - Mechanism
Amide
147
Lidocaine - Duration
Rapid absorption
Intermediate duration of action
148
Bupivacaine - Mechanism
Amide
149
Bupivacaine - use
Post-op pain control
150
Bupivacaine - Adverse affect
Greater cardiotoxicity
Binds more Na channels
Dissociates slower from the channels
151
Proparacaine - Mechanism
Amide
152
Proparacaine - Action
Fast onset
Short duration
Cats = 15 min
Dogs = 45 min
153
Mepivacaine - Mechanism
Amide
154
Mepivacaine - Use
Equine limb block
Diffuses through surrounding tissue
Les postinjection edema
155
Benzocaine - Mechanism
Ester
156
Benzocaine - Use
Topically absobed -
Lozenges
Fish anesthesia
