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176 Cards in this Set

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Primary body systems of focus for pre-anesthetic evaluations
Nervous
Cardiovascular
Pulmonary
Hepatic
Renal
First stage of preanesthetic assessment
Should occur 1-7 days prior to anesthesia, to pursue further diagnostics & treat any abnormalities beforehand
Second stage of preanesthetic assessment
An abbreviated evaluation that should occur when the patient is admitted, usually the only part of the assessment that is performed
Main components of the preanesthetic evaluation
history & physical exam

blood work & other diagnostics needed only when indicated by abnormalities in the history/physical
Major Components of the History
Signalment
Main Complaint
History of present illness
Medical history
Current health status
Systems review
Systems Review
Series of open-ended questions about each system of concern: general health, nervous, cardio, pulmonary, GI, urinary, musculoskeletal, skin
Fasting for anesthesia
reduces risk of regurgitation & aspiration, minimum of 6 hours for Ca & Fe
Concurrent medications with anticipated anesthesia
Meds should be given regularly, but not between anesthetic premed & induction
Drugs to consider with anesthetics
aminoglycosides, barbiturates, B-blockers, Ca channel blockers, carbonic anhydrase inhibitors, chloramphenicol, corticosteroids, digitalis, H2 blockers, NSAIDs
Usual minimum basic Clin Path tests performed for preanesthesia
PCV, TP, BUN
Electrocardiogram in preanesthetic assessment
Needed for older & traumatized patients, as well as those with known/suspected heart diseases
ASA Classifications
Summarizes the patient-related factors ONLY that contribute to the risks of anesthesia
ASA Category I
Excellent Risk: normal, healthy animal, for elective surgery
ASA Category II
Good Risk: Neonatal or geriatric, patients with mild systemic diseases, mild obesity, simple fractures
ASA Category III
Fair Risk:Patients with moderate systemic disease, fever, moderate dehydration/hypovolemia, chronic heart/renal disease
ASA Category IV
Poor risk: Severe systemic disease that threatens life, shock, severe dehydration, anemia, diabetes, cardiac/ renal/hepatic/pulmonary disease
ASA Category V
Guarded risk: moribund patients: not expected to survive 24 hours, severe shock, DIC
ASA E designation
designates an emergency case in which there isn't time for proper evaluation & preparation
Locations of opioid receptors
brain, spinal cord
myenteric complexes of the GI tract, kidney, heart, adrenal gland & joint capsules
Types of opioid receptors
Mu
Delta
Kappa
Effect of opioids
ANALGESIA
sedation
euphoria
dysphoria
excitement
3 Main sites of opioid action
1. inhibt pain transmission in dorsal horn
2. inhibit somatosensory afferents @ supraspinal level
3 activation of descending inhibitory pathways
Full agonist opioids
MORPHINE
high affinity and activation @ all relavent receptors
Profound analgesia & significant side effects
higher dose=higher effect, no limit to effect (death)
Partial agonist opioids
Buprenorphine
affinity at only some receptors, with significant activity @ those receptors
Agonist-Antagonist opioids
Butorphanol
agonists @ some opioid receptors, antagonists @ others
Full antagonist opioids
naloxone
have affinity for opioid receptors, but have no activity: used as reversal agents, block agonists
Opioid effects on Cardiovascular system
minimal: some bradycardia
Opioid effects on respiratory system
potentially potent depressents
↓resp rate & volume
initial tachypnea
Opioid effects on CNS
relieve pain w/o blocking motor activity or consciousness
CNS depressent in dog
CNS excitement in cat, horse, cow, sheep
Vomitting stimulation
Hypothermia in dogs
Other opioid effects
pupillary constriction (miosis) in dog, rabbit, rat
pupillary dilation (mydriasis) in cats, horses
intial emptying of GI tract when given
Metabolism of opioids
LIVER
urinary excretion
Opioid agonists to know
Morphine Sulfate
Hydromorphone
Oxymorphine
Fentanyl
Effects of Morphine Sulfate
Opioid agonist
causes histamine release when given IV
excitement in cats
vomitting
Lasts 4-6 hours
Effects of Hydromorphone
more potent & more expensive than morphine
less nausea, emesis & sedation than morphine
but does not cause histamine release
lasts 4-6 hours
Effects of Oxymorphone
10 times more potent & more expensive than morphine
more sedation & less histamine release than morphine
Effects of Fentanyl
80-100 times more potent than morphine
highly lipophilic= rapid onset & short duration (30min)
rarely see histamine release
available as transdermal patch
Significance of Opioid potency
Higher potency=must lower the dose to compensate
Partial opioid agonist to know
Buprenorphine
effects of Buprenorphine
Partial Mu agonist=high affinity, partial activity
slow onset, long duration (8-12 hrs)
used for post-op analgesia
available intra-bucal for cats
Opioid Agonist-Antagonists to know
Butorphanol
Effects of Butorphanol
3-5 times as potent as morphine, w/ less resp. effect
affinity for Mu & Kappa receptors: agonist @ Kappa, antagonist @ Mu
Only lasts .75-1hour, & not really good for invasive procedures
Opioid Antagonists to know
Naloxone
Effects of Naloxone
A narcotic antagonist
high affinity for Mu recept.
rapid onset, short duration (15-45 min.)=multiple dosing to offset opioid agonists
liver metabolism
Factors determining amount of chemical restraint needed
Breed
Temperment
Physical condition
Procedure (pain, duration)
Concurrent meds
Familiarity w/ agents
When to use chemical restraint
-Less painful procedures w/ cooperative patients
-Local/Regional anesthetic possible instead of general
-No anesthetic machine avail.
-Outpatient procedures
-Very short procedures
-Need lower cost or to avoid inhalant (airway procedures)
Advantages of Chemical restraint
no environmental pollution
no anesthetic machine
maybe less cardiopul depress.
maybe faster changes in anesthetic depths
some reversible
Disadvantages of chemical restraint
-not be adequate for all procedures
-may be excessive for procedure
-"all or nothing"
-may not be as closely monitored as inhalants
Protocol for chemical restraint
combinations of agents used
-reduces dosages
-reduces unwanted side effects
-more ideal anesthetic state
-requires knowledge of drugs, their interactions and side effects
Use Effects of Acepromazine
Tranquilization excellent when in combination w/ opioids
Antiemetic
Potentiates analgesia of other drugs
Injection not painful
Use Effects of Diazepam
Minimal cardiopulmonary depression
Muscle relaxation
Used in combination with opioids for fragile patient
Reversible
Use Effects of Midazolam
Min cardiopulmonary depression
Muscle relaxation
Use with opioids for fragile patient, Reversible
Water soluble & compatible with other drugs solution
Use Effects of Xylazine
Sedation
Analgesia
Muscle relaxation
excellent in combination with
opioids
Reversible
More consistant with opioids
Use Effects of Medetomidine
Sedation
Analgesia
Muscle relaxation
excellent in combination with
opioids
Reversible
More consistant with opioids
Use Effects of Morphine
Analgesia
Some sedation
Minimal cardiovascular effects
Use Effects of Butorphanol
Mild analgesia
Some sedation
Use Effects of Oxymorphone
Profound analgesia
Some sedation
Reversible
Use Effects of Hydromorphone
Profound analgesia
Some sedation
Reversible
No histamine release
Use Effects of Thiopental
Rapid Onset & recovery from single dose
Inexpensive
Can be added to other sedatives if immobilization needed
Use Effects of Propofol
Titratable to effect
Rapid recovery even with repeated doses
Can be used in patients with hepatic or renal insufficiency
Use Effects of Ketamine And
Tiletamine
EXCELLENT IMMOBILIZATION in fractious animals when combined with other agents
Analgesia
Bronchodilation
IV use of ketamine & Diazepam can be titrated
Caution for use Acepromazine
Hypotension, Does not provide good chemical restraint when used as the sole agent
Lowers seizure threshold Longeronset of action (20-30 min., May cause Prolonged effects in some patients
Caution for use Diazepam
Not useful for sedation in healthy animals when used as sole agent
Diazepam not water soluble
Variable absorption when given IM
Caution for use Midazolam
Not useful for sedation in healthy animals when used as sole agent
Diazepam not water soluble
Variable absorption when given IM, Costly
Caution for use Xylazine
Cardiopulmonary effects=↓ significant
Avoid in urinary tract obstruction cases
Only recommended for "young, healthy, exercise tolerant animals
Caution for use Medetomidine
Cardiopulmonary effects=↓ significant
Avoid in urinary tract obstruction cases
Only recommended for "young, healthy, exercise tolerant animals
Caution for use Morphine
Histamine release
Respiratory depression
Bradycardia
Emesis
Caution for use Butorphanol
Few side effects
Caution for use Oxymorphone
Bradycardia
Respiratory depression
Emesis
Caution for use Hydromorphone
Bradycardia
Respiratory Depression
Emesis
Caution for use Thiopental
Recovery may be rough
Significant cardiopulmonary depression
Must be given IV
Repeated doses may lead to prolonged recovery
Caution for use Propofol
Must be given IV
Strict aseptic handling
Cardiopulmonary depression
Heinz bodies in cats after repeated daily doses
Caution for use Ketamine and
Tiletamine
Psychogenic effects
Do not use in patients with seizures
May have prolonged rough recoveries especially in dogs
Significance of vapor pressure
The greater the vapor pressure, the greater the
concentration of the drug deliverable to the patient.
Significance of Solubility
Determines uptake and
distribution within body
Significance of Partition coefficient
Concentration ratio of an anesthetic in the solvent and gas phases Blood:Gas partition
coefficient
The ultimate goal of inhalant anesthetic
to achieve an adequate partial pressure(Panes) in the brain to cause the desired level of CNS depression
Factors that determine Alveolar partial pressure
Anesthetic input
Anesthetic uptake
Factors that determine Anesthetic input
 Ventilation
 Inspired concentration
 Breathing system
Factors that determine Anesthetic uptake
 Solubility
 Cardiac output
 Alveolar to venous partial pressure difference
Significance of Alveolar partial pressure
P(Alveolus) --> P(artery) -->

P(brain)
MAC definition
Minimum alveolar concentration
Significance of MAC
Min. alveolar concentration of an anesthetic that produces
immobility in 50% of subjects exposed to a noxious stimulus
How to measure MAC
Usually measured in volumes %
Factors that do not affect
MAC
 Species
 Duration of anesthesia
 Gender
Factors that increase MAC
 Hyperthermia
 CNS stimulants
 Hypernatremia
 Hyperthyroidism
Factors that decrease MAC
 Hypothermia
 CNS depressants
 Hyponatremia
 Hypothyroidism
 Pregnancy
 Hypotension
 Anemia
 Hypoxia
 Age
Popular inhalant anesthetics
Isoflurane
Sevoflurane
CNS effects of Isoflurane/Sevoflurane
CNS depression
Decrease in cerebral metabolic oxygen requirements
Increase in cerebral blood flow
Cardiovascular effects of Isoflurane/Sevoflurane
 Decrease in mean arterial blood pressure
 Increase in heart rate
 Decrease in cardiac output
Respiratory effects of Isoflurane/Sevoflurane
Dose dependant depression
Other effects of Isoflurane/Sevoflurane
-Decrease renal blood flow and glomerular filtration rate
-Reduction in liver blood
flow and oxygen delivery
Isoflurane metabolism
0.2% undergoes hepatic
metabolism
MAC & B:G partition coefficient of Isoflurane
MAC=1.3%

B:G=1:1.4
Metabolism of Sevoflurane
3-5% undergoes hepatic metabolism
MAC & B:G partition coefficient of Sevoflurane
MAC=2.4%

B:G=1:0.7
Why give Anesthetic Premeds?
↓anesthetic requirements
Calm/↓ stress, ↑ safety
Smooth anesthetic period
Sedation, Analgesia
Muscle relaxation, ↓ vomitting/regurg
Classes of Drugs used for Premed/sedation?
Anticholinergics
Tranquilizers/sedatives
Opiods
Anticholinergic drugs for premed/sedation?
Atropine
Glycopyrrolate
Tranquilizers/sedatives for premed/sedation?
Phenothiazines
Benzodiazepines
Alpha-2 agonists
Why give anticholinergics as premeds?
prevent/treat bradycardia
decrease secretions
How Anticholinergics work?
bind to muscarinic cholinergic receptors & prevent ACh from binding
Physiologic effects of Atropine
Cardio: ↑ HR, ↔ in BP
Resp: bronchodilation,
↓ secretions
CNS: readily crosses BBB
Other: Dilates pupils
↓ tears, ↓ GI motility
When not to give atropine
Not good for LA- GI stasis

patients w/ glaucoma, synechia, tachycardia
Metabolism of Atropine
Liver

Cats, rats & rabbits burn through fast b/c atropine esterase
Physiolog effects of Glycopyrrolate
Cardio: ↑ HR, ↔ in BP
Resp: bronchodilation,
↓ secretions
Other: ↓ GI motility
CNS: DOES NOT CROSS BBB
Primary differences between Glycopyrrolate & atropine
Glyco=no CNS signs, lower doses needed
Longer duration of action
Less likely to cause arrhythmias
Phenothiazine sedatives
Acepromazine
Acepromazine mechanism of action
Blocks dopamine @ post synapse
Blocks serotonine & Alpha-1 receptors
Reasons for giving Acepromazine
Sedation
Antiemetic
antiarrhythmic
Antihistaminic
Antipuritic
CNS effects of Acepromazine
CNS depression
↓ seizure threshold
Depresses thermoregulation
potentiates opioid sedatives
No analgesia
Cardio & Resp effects of Acepromazine
↓ BP
↓ PCV & TP
↓ Platelets function
minimal RESP effects
Other effects of Acepromazine
Muscle relaxation
Delayed gastric emptying
penile prolaspe
Onset/duration of Acepromazine
onset: 20-30 minutes
duration: 3-6 hours
Reasons for Benzodiazepine administration?
sedation
muscle relaxation
anxiolysis
anticonvulsant
How Benzodiazepines work?
GABA agonist-increases action, increases frequency of opening, hyperpolarizes neurons= less excitable
Benzodiazepines used
Diazepam
Midazolam
Zolazepam
Benzodiazapine antagonists
flumazenil
Physiologic effects of Diazepam
Minimal effects on Cardiovascular & Resp
CNS= calming w/o sedation, anti-convulsant, muscle relaxant
Paradoxic excitement
Pelcularities of Diazepam
Comes in propylene gylcol vehicle= IM absorption can be unpredictable
Paradoxic excitement in both cats & dogs
Effects of midazolam
Minimal effects on Cardiovascular & slight Resp depression
CNS= calming w/o sedation, anti-convulsant, muscle relaxant
Pelcularities of midazolam
More predictible than diazepam
Shorter duration than diazepam
prohibitively expensive for most vet medicine
What to know about Zolazepam
only used with tiletamine
works the same as other benzodiazepines
Dogs burn through fast, for faster recovery
Flumazenil
Benzodiazepine antagonist
high affinity for receptors
reverses cardiopulmonary & anticonvulsant effects
works in 2-4 minutes, only lasts 60 minutes so may need to redose
most useful in field work
Alpha-2 agonists to know
Xylazine
Medetomidine
Detomidine
Romifidine
Reasons for administration of Alpha-2 agonists
Sedation
Analgesia
Muscle relaxation
Sympatholysis
Action of Alpha-2 agonists
Binds Alpha-2 receptors, reduces sympathetic discharge & reduces norepinephrine release
Cardiovascular effects of Alpha-2 agonists
↓HR
arrhythmogenic
initial ↑BP, followed by hypotension
Respiratory effects of Alpha-2 agonists
↓rate & depth of breathing
CNS effects of Alpha-2 agonists
Sedation
Muscle relaxation
Analgesia
(personality changes-humans)
Other effects of Alpha-2 agonists
Emesis
Altered GI function
Hypothermia
Hypoinsulinemia
increased uterine tone
Mydriasis
Increased urine production
Xylazine
Least selective Alpha-2
works in 3-5 minutes IV, but only last an hour
causes relaxation of the larynx=risk of aspiration pneumonia
Detomidine
More selective than xylazine
used more in LA, because greater potency (can give less)
last ~ 2 hours
Medetomidine
VERY Selective alpha-2 agonist
only used in SA
Romifidine
Recently approved
Very selective alpha-2 agonist
Pecularities of Alpha-2 agonists
don't really work if the patient is excited before giving
reserved for young, healthy exercise-tolerant patients
Alpha-2 antagonists
Tolazoline
Yohimibine
Atipamezole
Reversal agents
Yohimibine
Alpha-2 antagonist
enhances Norepi release
can cause hyperexcitement, tachycardia, hypotension
Tolazoline
Least selective Alpha-2 antagonist
Induces H-2 effects-GI bleeding, diarrhea
Atipamezole
Most selective Alpha-2 antagonist
doesn't really act @ other receptors
don't need to redose
Characteristics of the Ideal injectable anasthetic
Water soluble
Long shelf life
stable in light
small volumes needed
wide margin of safety
Short duration of action
Analgesia
Muscle relaxation
No life-threatening changes
Classes of Injectable Anesthetics
Barbituates
Propofol
Etomidate
Dissociatives
Types of Barbituate Anesthetics
Long acting- Phenobarb
Short acting- Pentobarb
Ultra short acting- Thiopental
CNS effects of Barbituate Anesthetics
GABA agonist- enhances & mimics GABA action= hyperpolarization of neurons
CNS Depression
No analgesia
Cardiovascular effects of Barbituate Anesthetics
↑ HR
↓ SV & contractility
↓ BP
may cause ventricular arrhythmias
Resp. effects of Barbituate Anesthetics
Potent depressants
↓ tidal volume & rate
Altered sensitivity to CO2
Other effects of Barbituates
Hypothermia
Tissue Sloughing when not injected into a vein
cross placenta
No effect on GI, liver or kidneys
Factors affecting depth of anesthesia when using barbituates
Dose-amount, route, & rate
Ionization-
Protein binding-less= deeper depth
How Ionization of bartituates affects the depth of anesthesia
more ionized=less active= lighter depth
more alkaline solution=more ionized
more acidic solution=more nonionized=deeper plain
Factors affecting duration of barbituates
Redistribution=how long it stays in the brain
Metabolism
Redistribution of barbituates
Vessel rich=brain, liver=most of cardiac outpur
Lean=muscle
Fat-
Vessel poor=bone
highest [brain] w/in a min. of injection, lean 10-15 min.
stays in fat, repeated dosing= longer anesthetic time
Unique properties of Propofol
Insoluble in water-comes as an emulsion
used for induction & for maintenance
stable @ room temps & in light
No preservative=bacteria can grow, & get endotoxins production... throw it away after a few hours of being open
CNS effects of Propofol
↓intracranial pressure
unknown/unclear affect on seizure activity
Action of Propofol
GABA agonist
Cardiovascular effects of Propofol
↑ HR
↓ SV & contractility
↓ BP
may cause ventricular arrhythmias
Resp. effects of Propofol
Periods of apnea
Mild hypercapnia
Other effects of Propofol
Oxidative RBC injury, with repeated dosing
No perivascular sloughing, as with barbituates
Metabolism & excretion of propofol
Onset w/in 10 min.
Recovery w/in 20-30
hepatic & likely "extra" hepatic metabolism
non-cumulative effect, recovery w/in 30 min of last shot, no matter how many you give
Etomidate
A non-barbituate
Imidazole derivative anesthetic
insoluble in water= has propylene glycol vehicle
CNS Effects of Etomidate
acts on GABA receptors
↓ cerebral BF & intracranial pressure
no analgesia
Myoclonic movements
Cardiovascular effects of etomidate
No significant effects on any part of cardio system

Can use in patients w/ heart disease
Respiratory effects of etomidate
Slight depression
Other noteable effects of etomidate
pain @ injection site
Adrenal suppresion
Nausea & vomiting-during induction & recovery possible
Metabolism of etomidate
Rapid onset
Rapid hepatic metabolism
rapid recovery
Dissociative anesthetics
Ketamine
Tiletamine
makes patient dissociated/unaware of the environment
Ketamine
A dissociative anesthetic
Trance-like state
Immobility
Versatile
Chemical characteristics of Ketamine
low molecular weight
high lipid solubility
=rapid onset time
CNS effects of Ketamine
Dose related unconsciousness & analgesia
↑ cerebral BF & intracranial pressure
don't use in epileptic/ head trauma patients
Hallucinations
Cardiovascular effects of ketamine
has indirect effects
↑ HR, BP & CO
↑ myocardial O2 consumption
Respiratory effects of ketamine
Apneustic ventilation
↓ Resp. rate & minute volume
does not depress resp. response to hypoxia
↑ trachial secretions (use w/ anticholinergic to ↓)
Other noteable effects of ketamine
↑ intraocular pressure
limb ridigity
spontaneous limb movements
Eyes stay open (need to protect & keep moist)
Admin of Ketamine
IV or IM
Rapid onset (30-90 seconds-IV)
Lasts 3-10 minutes
Dogs metabolize, cats excrete unchange
Tiletamine
Only available in combination w/ zolazepam = telazol
Longer duration & more analgesia than ketamine
CNS effects of Telazol
Dose related unconsciousness & analgesia
↑ cerebral BF & intracranial pressure
Hallucinations
Not enough for deep, visceral procedures
Cardiovascular effects of Telazol
has indirect effects
↑ HR, BP & CO
↑ myocardial O2 consumption
Respiratory effects of Telazol
Apneustic ventilation
↓ Resp. rate & minute volume
does not depress resp. response to hypoxia
↑ trachial secretions (use w/ anticholinergic to ↓)
Species difference in using Telazole
Onset times rapid (minutes)
Dogs burn through much fast about an hour, w/ hepatic metabolism
Cats last longer, 3+ hours, excreted unchanged