VN Q2 General Anesthesia

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Use of opiods: preanesthetics
induction agents
analgesics
opiods mode of action: may act as agonists or antagonists on receptors
opiod effects (2): 1) CNS effects - depression or excitement. cats may exhibit bizzare behavior patterns.
2)Analgesia
neuroptanalgesia: opiod + tranquilizer

state of profound sedation and analgesia
opiod adverse effects (3): 1) depress respiration
2) increased peristalic movement
3) addiction
opiod reversability: 1) nalaxone
2) butorphanol (opiod)
4 components of general anesthesia: preanesthesia
induction
maintenance
recovery
Variables to be accessed every 5min during anesthesia: respiration depth and character
MM color
CRT
HR
pulse strenght and rate
jaw tone
eye position
palpebral reflex
O2 rate & O2 tank pressure
IV catheter placement & fluid administration rate
Temp
titration: drug given in a series of bolus injections, discontinuing when desired depth of anesethesia is reached
Stage I: immediately after induction
Stage II: involuntary excitement, not enough receptors hit
Stage III: under anesthesia
Stage IV: moribund
respiration during stage 1: normal, may be panting, rr 20-30bpm
respiration during Stage 2: irregular, may hold breath or hyperventilate
respiration under Stage 3, plane 1: regular 12-20
respiration during stage 3, plane 2: regular, may be shallow, 12-16
respiration stage 3, plane 3: shallow, <12bpm
respiration under Stage 3 plane 4: jerky
respiration under stage IV: apnea
cardiovascular function under stage 1: hr unchanged
cardiovascular function under stage 2: hr may increase
cardiovascular function stage 3, plane 1: pulse strong, hr > 90
cardiovascular function stage 3 plane 2: hr > 90
cardiovascular function stage 3 plane 3: 60-90 CRT increased, pulse less strong
cardiovascular function stage 3 plane 4: <60 prolonged CRT, pale mm
cardiovascular function stage 4: cardiovascular collapse
response to sx under anesthesia: plane 1 may respond w movement
plane 2 hr and rr may increase
eye position during anesthesia: stage 1 central
stage 2 nystagmus
plane 1 central or rotated, nystagmus
plane 2 rotated ventrally
plane 3 central or ventral
plane 4, stage 4 central
pupil size under anesthesia: stage 2 may be dilated
plane 1 normal
plane 2 slightly dilated
plane 3 moderately dilated
plane 4, stage 4 widely dilated
pupil response to light during anesthesia: plane 2 sluggish
plane 3 very sluggish / absent
plane 4, stage 4 unresponsive
muscle tone under anesthesia: plane 2 relaxed
plane 3 greatly reduced
plane 4, stage 4 flaccid
reflexes under anesthesia: stage 2 exaggerated
plane 1 swallowing poor/absent
plane 2 patellar, ear flick, palpebral, corneal
normal rr: dogs 15-30 bpm
cats 20-40 bpm
normal hr: dogs 60-160 bpm
toy breeds - up to 180
cats 110-240 bpm
brick red mm: increased perfusion, vasodilation

early shock, fever, sepsis, systemic inflammatory response
brown mm: intravascular hemolysis
acetaminophen toxicity in cats
petechiae mm (red splotching): coagulation disorder
rr values during anesthesia: dog 8-15 cat 12-18
dog <8 cat <10
dog <4 cat <6
hr values during anesthesia: dog 70-120
cat 130-170
arterial blood pressure during anesthesia: dog 100 cat 120
dog <60 cat <100
dog <50 cat <80
temperature values during anesthesia: 100-102
Two major cyclohexamine drugs: ketamine
tiletamine (telazol)
Cyclohexamines mode of action: disrupt pathways within the cerebrum and CNS stimulation
Effects of cyclohexamines (4): muscle tone increased
reflexes exagerrated
sensitivity to light & sound
dissociative anesthesia
Adverse systemic effects of cyclohexamines (2): cardiac - tachycardia
apneustic respiration (breath holding)
adverse effects of cyclohexamines (5): tissue irritation
increased salivation
no eye closure
stormy recovery
personality changes
negative properties of barbiturates (2): high lipid solubility
long recovery - drug stays in body
barbiturates should not be given to (3): sighthounds - little body fat
animals in shock hepatic/renal disease
adverse effects of barbiturates (5): respiratory depression
reduction in tidal volume
tissue necrosis
cardiac arrhythmias
excitement during induction/recovery
tiletamine/telazol: cyclohexamine
less apneustic respiration
prolonged recovery
Propofol - use, advantage, systemic effect: may be used as sole agent
rapid recovery, regardless of amount given
minimal cardiac effects
chlorofluorocarbons: halothane, isoflurane, sevoflurane

methoxyflurane (lesser degree)
gas anesthetics mode of action: inhibit breakdown of GABA, an inhibitory neurotransmitter. levels increase in brain and inhibit nerve function
distribution, elimination, & action of inhalant agents: concentration gradient between
alveoli, blood supply and brain
solubility coefficient: measures distribution of gas between blood and gas in the body.

low = enters circulation and escapes to brain

high = absorbed in other tissues and less "escapes" to brain with less concentration gradient in alveoli
properties of halothane (4) advantage disadvantage vapor pressure: fairly rapid induction & recovery

moderate rubber solubility

high vapor pressure
needs precision vaporizer
tiletamine / telazol: less apneustic respiration
may be prolonged recovery
propofol advantages (5): minimal cardiac effects
safe in sighthounds
rapid wakeup, onset, & duration (only 5-10min)
may be titrated w/o prolonged recovery
some muscle relaxation
propofol disadvantages (3): cannot be stored > 6 hours
some respiratory depression in 1st minutes
no analgesia
propofol uses: induction
sole agent for short procedures
list 1 advantage of etomidate and 3 disadvantages type of drug: Little systemic effects

Vomition
IV injection - painful
Phlebitis

imidazole
qualities of ideal inhalation agents (8): 1. minimal toxicity
2. ease of administraiton
3. rapid induction
4. good relaxation
5. good analgesia
6. cost
7. easy to handle
8. easy to control depth
Ether: inhalation anesthetic

not used
airway irritation
increased salivation
explosive
chloroform: inhalation anasthetic

not used
carcinogenic
nitrous oxide: gas inhalant anesthetic
used more in human than vet medicine
blue tank
chlorofluorocarbons (4): halothane
isoflurane
sevoflurane
methoxyflurane
mode of action of gas anesthetics: Inhibit breakdown of GABA, an inhibitory transmitter.
solubility of gas anesthitics in order from most to least: methoxyflurane
halothane
isoflurane
sevoflurane
vapor pressure if high, the drug is... Vapor pressure of halothane & iso vs sevuflurane: Measure of the tendency of anesthetic molecule to evaporate at 20C (room temp)

Volatile = high vapor pressure

Halothane & Isoflurane higher than Sevuflurane
low solubility coefficient: rapid induction & recovery

enters circulation and escapes to brain
High Solubility Coefficient: Slow recovery

Drug absorbed in other tissues and less "escapes" to brain with less concentration gradient in alveoli.
Minimal Alveolar Concentration What is more potent? Anesthetics Lowest to Highest MAC: Lowest concentration that produces no response in 50% of patients exposed to pain stimulus.

Low MAC = more potent.

Lowest to highest:
Methoxyflurane, Halothane, Isoflurane, Sevoflurane
Halothane adverse effects (8): Vasodilation & resp depression
Depressive effect on myocardium
Sensitizes heart to catecholamines

Increases vagal tone
Moderate lipid solubility

May cause livery toxicity
Malignant hyperthermia

Little analgesia
Isoflurane advantages (9): Quick recovery
Safer
Highest MAC
Low solubility coefficient
Low rubber solubility
Stable at room temp
Does not effect myocardium
Good muscle relaxation
No malignant hyperthermia or liver toxicity
2 Advantages of Sevoflurane: Very rapid induction & recovery
Easy adjustment of anesth. level
Tidal Volume Which drug lowers it?: Amount of gas inhaled
15ml/kg

Barbiturates
Minute Respiration Volume: amount inhaled in 1 minute

rr x (kg x 15ml)
Path of gas in anesthetic machine: O2 tank, gas pressure gauge, gas pressure regulator/reducting valve

Flowmeter - Vaporizer - Fresh gas inlet

Inhalation valve - Inhalation hose - ET tube - Patient - Exchalation hose - Exhalation valve - Pop-off valve - Reservoir bag

scavanger, CO2 absorber canister
Contents of full E cylinger of oxygen: 2200 psi
Contents of oxygen tank which is half full: 1100 psi
Liters of oxygen in tank: psi x 0.3
Oxygen tank should be changed at: 100-200psi
Advantages of cuffed ET tubes (3): 1. Prevent leakage of waste gas
2. Reduces risk of aspiration of material into lungs
3. Prevents breathing of room air
Tank Pressure Gauge: Indicates pressure of oxygen being delivered
function of Pressure-reducing valve / pressure regulator: reduces oxygen pressure to 40-50 psi
Flowmeter: Sets gas flow rate to patient
L/min
Reduces pressure from 50 to 15 psi
Function of vaporizer: Converts liquid anesthetic to vapor state
Adds controlled amounts of vaporized anesthetic to carrier gas
function and components of breathing circuit: Carries anesthetic and oxygen from vaporizer to patient and conveys expired gas away from patient.
4 Functions of Reservoir Bag: "Bagging" (manual ventilation)
Observation of respirations
Movement of bag indicates that ET tube is within trachea
Stores gas
function of unidirectional valves: Allows gases to flow in only one direction (toward the patient)
Bagging: Reservoir bag squeezed forcing 02 into lungs

1. Helps reverse atelectasis (alveoli collapse)
2. Flushes airways and alveoli with fresh gas, removing increase CO2
3. Artificial respiration
Minimum volume of reservoir bag: 60ml/kg
Pop-off valve / Pressure release valve: Allows access gas to exit from anesthetic circuit and enter scavenging system
Carbon Dioxide Absorber: Contains absorbing chemicals such as soda lime or barium hydroxide lime
Oxygen Flush Valve Rate of O2 delivery: Allows oxygen to bypass the flowmeter and vaporizer and enter the machine between unidirectional valves.

Pure O2 is delivered directly to breathing circut at rate of 35-75 L/min.
function of pressure manometer: Measures pressure of gases within the breathing system
Negative pressure relief valve: opens and admits room air to the circut if negative pressure (vacuum) is detected in circuit
Etomidate is particularly well suited for induction of dogs with which of the following problems? a) Severe cardiac disease b) Renal failure c) Orthopedic disease d) Pediatric (younger than 4wks): a) Severe cardiac disease
True or False Injectable drugs that are highly fat soluble are likely to be taken up by the brain more quickly that drugs that are not fat soluble.: True
Which of the following is an example of a dissociative anesthitic? a) Thipental sodium b) Pentobarbital sodium c) Ketamine hydrochloride d) Propofol: c) Ketamine hydrochloride
True or False One of the disadvantages of the drug methohexital is that animals that are anesthetized with it often may demonstrate excitement during recovery: True
True or False Metabolism and elimination of ketamine hydrochloride are the same in the dog as they are in the cat: False
Compared with methoxyflurane, halothane is considered to have a a) Higher vapor pressure b) Similar vapor pressure c) Lower vapor pressure: a) Higher vapor pressure
True or False Halothane may sensitize the heart to catecholamines: True
True or False Halothane is moderately soluble in rubber, which may result in the release of this gas from anesthetic equipment.: True
An anesthetic agent that has a low solubility coefficient will result in ___________ induction and recovery time a) Slow b) Moderate c) Fast: c) Fast
Which of the following has the lowest solubility coefficient a) Halothane b) Isoflurane c) Methoxylflurane d) Sevoflurane: d) Sevoflurane
As a rough guideline, to safely maintain a surgical plane of anesthesia, the vaporizer should be set at _________ x MAC a) 0.2 b) 1 c) 1.5 d) 2 e) 2.5: c) 1.5
True or False Isoflurane is a more potent cardiac depressant than halothane: False
Propofol sometimes causes transient apnea. To avoid this, the anesthesiest should: a) Give by infusion only b) Premedicate with opiods c) Administer IV only d) Titrate this drug in several boluses: d) Titrate this drug in several boluses
To be considered effective, nitrous oxide should be used at a minimum concentration of a) 3% b) 30-40% c) 50-60% d) More than 80% e) None of the above ranges are correct: c) 50-60%
One problem frequently associated with recovery from tiletamine-zolazepam in dogs is: a) Excitement b) Bradycardia c) Hypotension d) Laryngospasm: a) Excitement
Effects of halothane on the body include: a) Vasodilation b) Nystagmus c) Sensitization of myocardium to catecholamines d) Depression of myocardial cells e) Respiratory depression: a, c, d, e

No nystagmus
Effects that barbiturates may have on the body include: a) Reduction of respiratory rate b) Tachycardia c) Cardiac arrhythmias d) Decreased blood pressure: a, c, d

no tachycardia
The concentration of barbiturate entering the brain is affected by a variety of factors such as: a) Perfusion of the brain b) Lipid solubility of drug c) Plasma protein levels d) Blood pH of the animal: a, b, c, d
Effects that are commonly seen after administration of a cyclohexamine drug include: a) Increased blood pressure b) Increased heart rate c) Increased CSF pressure d) Increased intraocular pressure: a, b, c, d
Effects that isoflurane may have on the body include: a) Hepatic toxicity b) Accumulation in body fat stores c) Depression of respiration d) Seizures during recovery: c) Depression of respiration
MAC will vary with: a) Temperature of patient b) Age of patient c) Concurrent use of other drugs d) Anesthetic agent: a, b, c, d
Factors that may affect the speed of the induction process with a volatile gaseous anesthetic include: a) Solubility coefficient of the agent b) Vaporizer setting c) MAC of the agent d) Concurrent use of atropine: a) Solubility coefficient of the agent
b) Vaporizer setting
Nitrous oxide may be included as part of an anesthetic protocol because it: a) May provide a second gas effect b) Will reduce the amount of volatile anesthetic needed c) Has minimal depressant effects on the respiratory or cardiovascular c: a, b, c
When pentobartital sodium is used as an anesthetic, which of the following may be noted: a) Relatively slow onset of action b) Respiratory depression c) Poor analgesia d) Slow recovery e) Easily reversed: a, b, c, d

Not easily reversed
Which of the following drugs may be safely and effectively given IM or IV in a cat? a) Thiopental sodium b) Telazol c) Ketamine hydrochloride d) Methohexital sodium: b) Telazol
c) Ketamine hydrochloride
How are injectible anesthetics eliminated?: redistribution
liver metabolism
renal excretion
How are inhalation anesthetics eliminated?: exhalation from lungs
some undergo liver metabolism and renal excretion
List 5 types of injectable induction agents: barbiturates
cyclohexamines
etomidate
neuroptanalgesic agents
propofol
Classes or barbiturates: Intermediate acting (pentobarbital)
Short acting (thiopental)
Ultrashort acting (methohexital)
How are barbiturates used: Used as induction agents
Administered by titration
Pentobarbital Class Adverse effects (4): intermediate acting barbiturate

analgesia - none
respiratory depression
recovery prolonged
relaxation of muscle poor
Doxapram (Dopram): respiratory stimulant
may accelerate arousal from barbiturate or inhaltation anesthesia
2 Disadvantages of Sevoflurane: 1) Reacts with KOH or NaOH in soda lime to produce Compound A that can cause renal tubular damage in rats.

2) Greater heart and respiratory depression than isoflurane
Properties of Sevoflurane vapor pressure, solubility coefficient, Mean Alveolar Concentration: Vapor pressure: lower than isoflurane

Solubility coefficient: very low

MAC: greater than isoflurane
induction: process by which animal leaves conscious state
maintenance: stable level of anesthesia achieved
recovery: concentrations decrease in brain
injectable drugs metabolized
Safety of general anesthetics: 1) use premeds
2) reduce quantitiy of anesthetic w/ appropriate premeds
3) double check doses
4) titration
Thiopental/barbiturate induction: Stay within vein (use indwelling catheter)

1/2 dose over 10-15sec "bolus"

Immediate entrance to stage 3

If intubation not possible after 30sec give 1/2 remaining dose
Ketamine/tranquilizer induction: 1) Inject total quantity over 30-60sec or
2) give 1/2 as bolus over 15-30sec & rest in halves every 45sec
Propofol induction: slow IV
1/3 of dose every 30sec
careful of apnea
Advantages of inhalation anesthesia (5): 1) Greater margin of safety
2) Depth readily altered
3) Elimination via lungs
4) Constant delivery of O2
5) Emergency airway for mechanical ventilation
Disadvantages of inhalation anesthesia (2): Anesthetic machine required
Waste gas
Disadvantages of maintenance via injectable agents (4): 1) Not easy to control
2) Low margin of safety
3) Constant IV injection
4) Non safety access
0-5% dehydrated: Tent: skin immediately returns
CRT normal
Eyes normal
MM pink and moist
5-8% dehydrated: Tent 2-4sec delay
CRT 2 sec
Eyes slightly sunken in sockets
MM slightly dry or tacky
8-10% dehydrated: Tent 5-10sec delay
CRT 2-2.5sec
Eyes sunken in sockets
MM dry, slightly tacky
10-12% dehydrated: Tent 10-30sec
CRT 3+
Eyes very sunken
MM dry
Depressed
Signs of shock, cool extremities
Rapid, weak pulse
Tachycardia
12-15% dehydrated: State of shock, death is probable
Advantages ET intubation (4): 1) efficient delivery of anesthetic gas
2) improves efficiency or respiration, decreases anatomic dead space
3) delivers O2 directly to patient
4) reduces risk of aspiration
Disadvantages of ET intubation (9): 1) stimulate activity of vagus nerve
2) some species/breeds difficult to intubate
3) may damage larynx, pharynx or soft palate
4) many tubes designed for humans & are too long for vet use
5) pressure necrosis may result if cuff excessively inflated
6) may become obsructed by saliva, mucus, blood, foreign material
7) patient may chew tube in half
8) tubes reused - spread diseases, disinfectant may irritate tracha
9) irritation of tracha and larynx
reasons for hypothermia (6): 1) anesthetic depression thermoregulation in brain
2) shaving
3) decreased metabolic rate
4) no shiver reflex
5) opened body cavities
6) pediatric/geriatric patients can't regulate temp well (decreased glucose)
name, function: murphy endoctracheal tube

murphy eye helps prevent complete obsruction of tube if bevel is plugged

magill tube - no eye
name, use: cole endotracheal tube
used in small animals
name, use: tank pressure gauge
indicates pressure of O2 being delivered
name, use: precision vaporizer

designed to deliver exact concentration of gas selected
Mature fel Strong pulse, HR 144, rr 20, pupils central, palpebral reflex, no pedal or ear flick reflex. Stage? Is intubation possible? What other tests should be done?: Stage 3, plane 1

May be deep enough to intubate. Check jaw tone.
13yr k9, tumor removal, under 2% iso Respiration shallow, rr 8, hr 90, no response to sx, no reflexes, central pupils. Adequate anasthesia?: Stage 3, plane 3
Too deep, change to 1.5%
8yr k9, atropine, ket/val hr 100, rr 8, moderate jaw tone, pupils central, no response to light, no reflexes Appropriate depth?: Stage 3, plane 2 or 3

Uncertain of stage. Deep enough.
Collapse of alveoli: atelectasis

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