Test 1 Flashcards
1
Q
General anesthesia (unit 1) - a reversible state in which the CNS is affected by the drugs administered, which results in :
A
Loss of consciousness
Loss of pain sensation
Amnesia
Immobility
2
Q
When is general anesthesia used in small animals?
A
All internal surgeries
Most skin surgeries
Diagnostic procedures
Dentistry
Radiography
Orthopedic procedures
3
Q
When is general anesthesia used in large animals?
A
Cattle - mechanical restraint and local anesthetic
Equine - minor procedures (sedation) and major procedure (injectable or inhalant for general anesthesia
4
Q
Sequence of events going under general anesthesia :
A
Recovered
- amnesia
- loss of consciousness
- reduction in reflexes
- analgesia
- mild cardiovascular and resp depression
- severe cardiovascular and resp depression
- respiratory arrest
- cardiac arrest
Death
5
Q
Anesthetic protocols
A
Combos of drugs are often used to produce the overall desired anesthesia (cocktails)
6
Q
Anesthetic protocols : procedural needs
A
Muscle rigidity
Excessive salivation
Pain level
7
Q
Anesthetic protocols : what to go off of to know the patient needs
A
Signalment
History
Temperament
Bloodwork
8
Q
Normal surgical plane illustrates the importance of :
A
Knowledge of drugs and expected effects
Constant monitoring of vitals
Monitoring of depth indicators
Changing anesthesia according to patient needs
Preparedness and prevention
9
Q
Pre-anesthetic history :
A
Current illness
Current medication
Prior history of anesthesia
Fasting history
10
Q
Pre-anesthetic pre-op exam:
A
TPR
MM and CRT
Auscultation
Oral cavity and pharynx
Breed
Temperament and activity level
Weight and BCS
Gender
Hydration status
11
Q
Pre-anesthetic prep diagnostic procedures:
A
PCV and TP
CBC
Blood chemistries
Urinalysis
Radiographs
ECG
12
Q
Pre-anesthetic prep release form:
A
Consent
Emergency contact
Written estimate
Resuscitation status
13
Q
Classifications of healthy but high risk
A
Obese animals (especially cats)
Sighthounds and thin breeds
Brachycephalics
Neonates
Geriatrics
Advanced pregnancy
14
Q
Classification of sick and at risk
A
Liver disease
Kidney disease
Cardiac disease
Respiratory disease
Shock
Anemia
Dehydration
15
Q
Pre-anesthetic conditions: Class I
A
C1 - minimum risk
Normal and healthy with no underlying disease
16
Q
Pre-anesthetic conditions: Class II
A
C2 - slight risk
Mild systemic disturbances; no clinical signs of disease
ie, obese animal
17
Q
Pre-anesthetic conditions: Class III
A
C3 - moderate risk
Moderate systemic disease or disturbances; mild clinical signs
ie, high temp
18
Q
Pre-anesthetic conditions: Class IV
A
C4 - high risk
Pre-existing severe systemic disease or disturbances
ie, skinny/emaciated animal
19
Q
Pre-anesthetic conditions: Class V
A
C5 - grave risk
Life-threatening systemic disease of disturbance
ie, organ failure
20
Q
Why do we withhold food before surgery?
A
Decrease the risk of aspiration and vomiting under anesthesia
(Aspiration pneumonia can be fatal within 12-24hrs)
21
Q
Why do we not withhold water every time?
A
Prevent dehydration before anesthesia and clears from GIT faster than food does
22
Q
Exceptions with fasting before GA
A
Neonates
Birds
Rabbits
Lab animals
Diabetics (often require dextrose supplements under anesthesia)
23
Q
What do pre-anesthetic medications do?
A
Given within 1hr of anesthesia
Calm or sedate
Synergistic effect of drug interactions = reduces the amount of anesthetic to induce and maintain
Counter act some negative side effects of anesthesia
24
Q
Pre-anesthetic drugs: Anticholinergics
A
Atropine and Glycopyrrolate
25
Characteristics of Atropine and Glycopyrrolate
Use when decrease in HR and RR
Dilates pupils
Increase resp secretions
Increase peristalsis
Decrease tear production
Block effects of bradycardia and excessive salivation
Decrease BM
Dilates bronchioles
26
Contraindications of anticholinergics
Elevated resting HR; can then cause tachycardia
Constipation
Certain eye conditions
Ophthalmic ointment causes pupils to dilate and prevents ciliary spasm, it is used to treat corneal ulcers and uveitis
27
Adding anticholinergics to opioids does what?
Decreases bradycardia and vomiting
28
Adding anticholinergics to xylazine does what?
Usually decreases bradycardia and arrhythmias
29
Adding anticholinergics to ketamine does what?
Usually decreases respiratory secretions (mostly used for induction)
30
Adding anticholinergics to pre-med does what?
Used for the treatment of bradycardia during surgery, less than 60-70bpm
31
Tranquilizers/sedatives
Acetylpromazine (acepromazine)
Diazepam
Xylazine
Dexmedetomidine
32
Characteristics of Acetylpromazine
Sedative
Antiemetic and antidysrhythmic
33
Cautions when using acetylpromazine
Causes vasodilation which may lead to decreased BP and hypothermia in compromise patients (only use in young and healthy animals)
Can increase aggression in some
Lowers seizure threshold
Prolapse of third eyelid
Provides no analgesia
34
Contradictions when using acetylpromazine
Aggressive animals
Most geriatric or compromised patients
Epileptics or seizure prone animals
Painful procedures
Eye surgery
Boxer breeds (British)
35
Characteristics of Diazepam
Not a strong sedative
Reduces anxiety
Can cause increased aggression in some
Good skeletal muscle relaxation
Commonly used with ketamine
Treats and prevents seizures
Minimal cardiac and respiratory side effects
Useful in sick and geriatric patients
IV route preferred (give slowly, could cause bradycardia)
Appetite stimulant, behavior, and treatment of post-op blocked cats
Caution of liver failure in cats
36
Characteristics of Xylazine
Potent sedative, muscle relaxation
Some analgesia
When being used for pre-anesthetic, reduce dose 50-80%
Causes emesis and 50% of dogs and 90% of cats
Can be used with ketamine for induction or short anaesthesia procedures
37
Cautions and contradictions of xylazine
Bradycardia
Hypotension
Arrhythmias
Respiratory depression
Bloat (avoid in deep chested dogs)
Metabolize by liver and excreted by kidney
May cause abortions in humans and animals
38
Characteristics of Dexmedetomidine
Becoming more and more common
May cause excessive sedation
Analgesia
Bradycardia
Pale gums and peripheral vasoconstriction
Can be used alone or in combination with other tranquilizers, opioids, or induction agents
With an opioid, it is useful for many things
Mixed to make kitty magic (butorphanol, ketamine, dex)
Caution in hepatic disease (hepatic metabolism)
39
Least to most analgesia in OPIOIDS
Butorphanol
Morphine (don’t use IV in cats)
Hydromorphone
Fentanyl
Buprenorphine (slow release SQ lasts longer)
40
Characteristics of opioids
Safer than most tranquilizers
Useful in cardiac and geriatric patients
May cause bradycardia, vomiting, and respiratory depression
Causes excitement in cats (avoid morphine)
Epidural use (butorphanol, oxymorphone, and morphine)
41
Characteristics of butorphanol
Common and safe in dogs and cats
Less cardiac and resp depression
Mixes well with other drugs
Controlled drug
Atropine not necessary
Short duration
Analgesia is weaker than some
42
Characteristics of oxymorphone
Excellent analgesia
Resp depression and bradycardia if not given with an anticholinergics
Expensive and difficult to get in Canada
43
Characteristics of meperidine
Decrease in use
Low resp and cardiac depression
Low intensity and short duration of analgesia
OVC premix: atropine, ace, and merperidine
44
Characteristics of Fentanyl
Very effective analgesic
Rapid onset and short duration
Combines with benzo as an induction agent
Common as a transdermal patch, but also given IM, SQ, or epidural (not common) which has a rapid onset and short duration of 30 mins
45
Time of effect for transdermal fentanyl patch
Dogs - 12-24hrs
Cats - 6-24hrs
Horses - 6+hrs
46
Characteristics of morphine
Not common
Good analgesic
Duration of action is 2-4hrs
Cheap
Severe resp depression
Vomiting and GI stimulation
Hypotension (esp IV use)
47
Characteristics of hydromorphone
Excellent analgesia but excessive sedation
Duration of action is 4–6hrs
Respiratory suppression
May cause bradycardia (pre-med with atropine)
Occasional excitement (less likely than morphine)
Can be used as premed, medication, and algesic, induction agent, and epidural
Useful and geriatric and compromise animals at lower doses
Transient hyperthermia in cats
Painting and vomiting in pre-medicated patients (less than morphine)
48
What is Neuroleptanalgesia
Almost anesthesia
When an opioid is combined with a tranquilizer
Good degree of sedation
Usually adequate for short procedures
Can be used for induction in compromised or geriatric patients
49
What does general anesthesia premedication do? (Unit 2)
Enable the patient to be easier to work with
Prevent side effects of anesthetic drugs
Preemptive analgesia
50
What is the outcome of general anaesthesia induction? (Unit 2)
To enable ET tube
51
What is included in general anesthesia maintenance? (Unit 2)
Keeping up the correct stage and plane
No movement, pain, or consciousness throughout the procedure
52
What are induction agents?
Drugs given to allow ET tube intubation prior to inhalant anesthesia maintenance
Can also be used for short term, injectable anesthesia
53
Induction principles
Induction agents are administered “to effect” for induction or short term restraint
Calculated doses drawn up into a syringe, but only 1/4-1/2 of the dose is given in short intervals, until jaw tone is relaxed
Many animals have respiratory depression after rapid IV bolus
54
Induction principles: episodes are most commonly seen with which drugs?
Thiopental
Propofol
Alfaxalone
55
Ultrashort barbiturates
Thiobarbiturates
5-15 mins
IV induction
Not common
THIOPENTAL
56
Short acting barbiturates
45-90 mins
IV, IM, IP, IC, euthanasia
IV for general anesthesia
PENTOBARBITAL
57
Long acting barbiturates
8-12hrs
PO anticonvulsants
PHENOBARBITAL
(The more lipids soluble the drug, the shorter or faster acting it is)
58
Method of use for thiopental
Drop the calculated dose and give 1/3-1/2 of the dose over 10 seconds
Over 1-2 mins, assess the jaw tone, MM colour, reflexes, and relaxation/movement
Lipid soluble
From arm to brain in 5-8 seconds
Gradual liver metabolism and kidney excretion
Concentration gradient (drugs moves from high to low)
59
Potential problems when giving thiopental too fast
TRANSIENT APNEA
Provide ventilation every 20 seconds if prolongs
Ventilation faster than 20 seconds can prolong apnoea due to decreased CO2 levels
60
Potential problems when giving thiopental too slow
EXCITEMENT PHASE (3-4mins)
Disorientation, vocalization, and excitement
Treat by giving more barbiturates or masking with inhalant
61
Cautions or avoid thiopental in:
Sighthounds
C-sections
Splenectomy
Cardiac diseases
Hepatic and renal disease
Resp disease
Thin animals
Obese animals
Hypoproteinemic animals
Hypothermic animals
Acidotic animals
62
Thiopental in Sighthounds
Avoid use
Prolonged recoveries
Lack of body fat
May have impaired hepatic function
63
Thiopental in C-sections
Avoid use
Rapidly diffuse across placenta into fetal blood and cause severe respiratory depression and fetuses
64
Thiopental in splenectomies
Caution
May cause splenic engorgement
65
Thiopental with cardiac disease
Decreases cardiac output
Decreases blood pressure (vasodilates)
Cardiac arrhythmias are not uncommon
66
Thiopental with hepatic and renal disease
Metabolized by liver
Kidney excretes metabolites
67
Thiopental with respiratory disease
Causes direct respiratory depression
Breath only when oxygen levels in the body are very low
APNEA —> hypercarbia + metabolic acidosis
68
Thiopental with obese animals
Dose on lean body weight
69
Thiopental with hypoproteinemic animals
Majority of the drug is protein bound, if low protein, more of the drug in active form is present
70
Thiopental in acidotic animals
Shock
Urinary obstruction
More of active non-ionized form of drug is present in acidotic blood
Normal dose may be toxic
71
Thiopental uses
Can be used in young and healthy patients
Safe for seizure prone animals and conditions of increased ocular pressures (drug causes decreased ocular and intracranial pressures)
Useful for larynx function exam
72
What are opioids used for?
Pre-anesthetics
Post-op analgesia
Neuroleptic combos
Can be used with sick or geriatric patients as induction
73
Dissociative agents
Cyclohexamine family
NMDA receptor agonist
Depress some parts of the brains and stimulates others (CNS short circuiting analogy)
Teletamine
PCP
Ketamine
74
Characteristics of Ketamine
Cats tolerate better than dogs when given IM
Causes CNS stimulation (increased muscle tone and reflexes, amnesia, catalepsy, superficial analgesia, lowers seizure threshold)
Increased salivation
Apneustic respirations are typical
Avoid use with seizure history patients
75
Recovery from ketamine
Rough
Put animal in quiet, dark, and padded area
Pre-op tranquilize
76
Ketamine with diazepam
Ketamine (100mg/ml)
Diazepam (5mg/ml)
Prepared in a 1:1 mixture in the same syringe at 0.1mg/kg
77
“DKT” or “kitty magic”
Dexmedetomidine (0.5mg/ml)
Ketamine (100mg/ml)
Butorphanol (10mg/ml)
1:1:1 mixture in the same syringe given 0.1mg/kg IM for feline
78
Ketamine and acepromazine
+/- atropine
79
Ketamine and xylazine
Not common due to side effects
80
Ketamine in large animal
First, give xylazine or dex IV
Then give ketamine IV after sedation
Avoid atropine in horses, due to possible colic side effects
81
Characteristics of Propofol
Phenol group
Pre-med animals get 4-6mg/kg
Non pre-med animals get 8-10mg/kg
1/2 bolus then rest to effect
Little analgesia
Great for C-sections
Minimal cardiac effect
Smooth and rapid recoveries, no hangover
Safe in all animals
82
Characteristics of Alfaxalone
Neurosteroid
IM in cats
Used in pre med or non pre med
Give over 60 seconds, 1/4 dose every 15 seconds until no jaw tone
Useful for induction maintenance
So you can C-sections and greyhounds
Little hangover, no analgesia
Can cause apnea
83
What is inhalant anesthesia? (Unit 3)
Vapours or gases given directly to the resp system, using an anesthetic machine for the purpose of maintenance anesthesia
84
Pros of inhalant anesthesia maintenance
Quick and easy titration for depth of anesthesia
Drug metabolism is less
Controlled by oxygen supplementation via a patent airway (ET tube)
85
Cons of inhalant anesthesia
Increased equipment and cost
Waste gas and environmental pollution
86
The ideal gas anesthetic is:
Low cost
Safe for anesthetist (non-explosive and non-flammable)
Safe and advantageous to patient
87
Inhalant oxygen pathway
Oxygen
Vaporizer
“Fresh gas”
Anesthetic machine circuit and breathing circuit
ET tube and patient airway
Alveolar wall
Concentration gradient
Blood stream
88
Inhalant agent pathway in reverse
Vaporizer turned off
Only oxygen to patient
Anesthetic leaves body tissue/brain
Anesthetic leaves the bloodstream
Lungs/alveoli
Expiration = majority of the anesthetic removed
89
3 characteristics used to compare the use and effects of inhalant anesthetics
Vapour pressure
Solubility coefficient
Minimum alveolar concentration (MAC)
90
4 kinds of inhalant anesthetics
Isoflurane (most common)
Sevoflurane (2nd most common - avian, exotics, and referral)
Halothane (no longer available)
Methoxyflurane (historical use)
91
Vapour pressure
Tendency of a liquid to evaporate at room temperature
92
HIGH vapour pressure
Evaporates very easily = very volatile anesthetic
93
LOW vapour pressure is :
Stable at room temperature = less volatile
94
Vaporizers
Volatile anesthetics require precision vaporizers to ensure high concentrations of anesthetic do not reach the animal
Most can be maintained at a concentration less than 5%
Isoflurane MAX concentration is 32%
95
Comparison of vapour pressures amongst inhalants
Isoflurane (32% or 250mmHg vapour room temperature)
Sevoflurane (22% or 170mmHg vapour pressure)
Halothane (32% or 243mmHg vapour pressure at room temperature)
96
Solubility coefficient
A measure of whether the anesthetic prefers to be in tissue or in a gas state
97
LOW solubility coefficient of an inhalant anesthetic agent causes:
Rapid inductions and rapid recoveries from anesthesia
Anesthetic depth changes are also more rapid
98
HIGH solubility coefficient causes:
Slower infections and slower recoveries
99
Minimal alveolar concentration (MAC)
Measure of the strength or potency of an anesthetic agent (the lower the MAC, the more potent the anesthetic)
Isoflurane - 1.5%
Sevoflurane - 2.4%
Halothane - 0.87%
Surgical plane of anesthesia is 1.5-2x MAC
HIGH MAC = needs less anesthesia
LOW MAC = more anesthesia
100
Factors increasing MAC
Metabolic acidosis
Age (geriatric)
Premedication
Pregnancy
Nitrous oxide
Local anesthetics
Severe hypotension
101
Factors decreasing MAC
Hyperthyroidism
Hyperthermia
Hypernatremia
Age (young)
Anxiety
102
Pros of Isoflurane
Require precision vapourizer
Relatively low solubility coefficient (rapid inductions and recoveries)
Relatively low MAC
Best for cardiac patients (less arrhythmogenic)
Best for hepatic and renal disease (removed by expiration)
Safest for geriatric, neonates, and humans
7-8x cheaper than sevo
103
Cons of Isoflurane
More respiratory depressive than halothane was
Pungent odour that may cause breath holding
No post-op analgesia
May cause excitement in recovery
104
Pros of Sevoflurane
Solubility coefficient is lower than iso, meaning rapid inductions, recoveries, and faster changes in the depth of anesthesia
Slightly less depression on ventilation than iso
Similar cardio side effects to iso
Minimal metabolism, less than 3% by liver and kidneys (more than iso)
105
Cons of Sevoflurane
More expensive
Requires its own vapourizer
MAC higher than iso
7-8x more expensive than iso
Less common in small animal
106
Characteristics of halothane
Was once the most common in vet med
Negative cardiac effects
Increased hepatic metabolism
Possible safety concerns for operating room personnel
107
Characteristics of methoxyflurane
Low MAC
Safer than halothane for cardiac patients
Most severe resp depressant (bag patient whole time)
Very high solubility coefficient = prolonged inductions and recoveries (50% metabolism by liver and excreted by kidneys)
Avoid in hepatic disease
Renal failure accounts in both patients and anesthetists exposed for long periods
108
Characteristics of Diethyl ether
1840’s
Good analgesia
Muscle relaxant
Better cardio safety than other at that time
Long term liver disease and cancer
Explosive and flammable
109
Characteristics of Nitrous oxide
High MAC - 188% in animals
Must be used in combo with halothane or methoxyflurane
Low solubility coefficient
Diffusion hypoxia
110
Define diffusion hypoxia
Following discontinuation of nitrous oxide, the concentration gradient between the gases in the lung and alveolar circulation rapidly reverses, leading to rapid oxygen dilution in the alveoli and subsequent hypoxia, and 100% oxygen administration should follow nitrous oxide cessation
