Flashcards in Test 3 Notes: Janet Deck (166):
taking patient from a conscious to an unconscious state
2 Methods of induction
4 Benefits of ET intubation
Establish pt. airway
Decrease gas exposure to personnel
3 Types of ET tubes
Cuffless ET tubes
Used for small animals & exotics
Skinny end inserted into trachea
Tie behind ears so wider part creates seal
Are easily dislodged
Beveled end (easier to insert)
Murphy eye (prevents complete blockage)
Pilot line with balloon
What are 3 benefits to using a cuffed ET tube
Prevents leakage of gas to room
Prevents animal from breathing in room air
Cuffs do NOT ____, they create a ____
Hold the ET tube in place, they create a seal
How are ET tubes measured?
french scale= external diameter
How do you choose an ET tube size?
Use a chart based on weight
Measure tube diameter in comparison to nasal opening
How is the length of the ET tube measured?
From the tip of the nose to the thoracic inlet
What could happen if the ET tube is too long?
Increased resistance to respiration
How should a patient be restrained for placement of the ET tube?
Restrainer holds top jaw
Extend neck and raise head
Intubator will pull tongue down to open mouth
Medical term for vocal folds
How do you restrain a ET tube?
What is the best way to know the ET is in the trachea?
**To visualize it
-use fingers to feel for tube between vocal folds
-feel air with exhalation
-res. bag movement
How would you know the ET tube is NOT properly placed?
You hear vocalization
What are 2 ways to know how much air to use in cuff
Back pressure in syringe
Use pressure manometer
What numbers do you look at when using the pressure manometer to inflate the cuff?
Hear slight leak at 20cmH2O
No leak at 15cmH2O
What could happen if you over-inflated the cuff?
Compression of the tube
Pressure necrosis of trachea
Why are cats more difficult to intubate?
Small trachea diameter
Larynx sits deeper in neck (harder to visualize)
Vocal folds cover more of the glottis
How would you intubate a cat?
Using a stylet or by putting lidocaine on the vocal folds
How much lidocaine would you put on the vocal folds?
one drop on each vocal fold
For feline intubation
Relaxes jaw tone and prevents spasms
What is the instrument that depresses the base of the tongue and has a light source?
What are some complications associated with ET intubation?
Pressure necrosis of lining of trachea
Plugged ET tube (mucus plug)
Stimulation of vagus nerve
Animal could chew tube during recovery
How long do you leave the cuff inflated when extubating the patient?
Until you see 2 good swallows or you see signs of recovery
What do you do if the animal vomits with an ET tube in?
Deflate the cuff 1/2 way and remove (the cuff acts a squeegee)
How are ET tubes cleaned?
With dilute antiseptic (like chlorhexadine)
OK to submerge under water
Inflate cuff to remove all mucus
Use brush or pipe cleaner to clean inside
Rinse and hang to dry with cuff inflated
What should you be aware of if lasers are being used during surgery?
The laser mixed with the high oxygen could start a fire
Wrap ET tube with duct tape
Use a special laser safe ET tube
What is the Corneal reflex
touch cornea with sterile swab, animal should blink and withdraw eye, should be present during surgical plane, more common in equine
What is the Ear flick reflex
Gently touch hairs on inside of ear and look for "flick" could be absent or present during surgical plane
More reliable in cats
What is the Palpebral reflex
Gently tap medial canthus of the eye and observe blinking reflex
Should be gone during surgical plane
What is Jaw tone
Open jaw and observe muscle tone, should have some tone but mostly relaxed
Puppies and kittens have weak jaw tone
Eye position & Pupil size
Usually eyes will rotate ventromedial during surgical plane but can also be central
Pupils should be slightly dilated during surgical plane
10 Common vital signs to monitor during anesthesia
Voluntary excitement phase- induction
Immediately after admin of injectable or inhalant (usually rougher and longer)
Animal is conscious, but disoriented
HR & RR can be normal or increased
All reflexes present
Involuntary excitement phase
Begins with loss of consciousness, all reflexes present, animal is able to chew and swallow
May have rapid movement of limbs, vocalization, struggling etc.
Shorter stage 2 = better!
Stage 3, plane 1
Light plane of anesthesia
Can be intubated
Relaxed jaw tone
NOT able to withstand sx.
Stage 3, plane 2
Medium plane of anesthesia
Suitable for most surgical procedures
Slight response to surgical stimulation
Patient is unconscious and immobile
What is the normal RR during Stage 3, plane 2?
Stage 3, plane 3
Deep plane of anesthesia
Significant depression of circulation and respirations
Excessively deep for most sx procedures
Good plane for very painful surgery
Marked muscle relaxation & slack jaw tone
NO surgical response
Stage 3, plane 4
Patient is too deep
Drop in HR, BP, CRT and pale MM
CPCR necessary to save patient
Turn off vaporizer
What are the 6 injectable anesthetic agents?
What are the 2 main uses for Barbiturates?
What is the ultra-short acting barbiturate?
(death row drug)
Primary use of Phenobarbital
Primary use of Pentobarbital
ONLY DOUBLE THE ANESTHESIA DOSE!
IV admin only
4 effects of barbiturates
excitement during induction and recovery (Prolonged stage 2)
2.Potent respiratory depression
apnea with rapid admin or high doses
decreased RR and depth
decreased BP and cardiac output
IV admin only
What breeds have increased potency with barbiturates?
Sighthounds & lean animals
Used to be used as induction agent
No longer made in the US
Best for use in sighthounds
Death row drug
What are the 2 Cyclohexamines?
Ketamine (Ketaset, Ketalar, Vetalar)
Tiletamine (in Telazol)
Cyclohexamine uses and properties
IV or IM admin.
Cyclohexamine mode of action
Disrupts or scrambles nervous system pathways so they never make it to the brain
"Trance-like" anesthesia- appears awake, but immobile and unaware
CNS effects of Cyclohexamines
-Increased CSF, intracranial pressure, and intraocular pressure
-Lowers seizure threshold
-Increased sensitivity to sound
What drug combined with Cyclohexamines can help decrease the rough recovery?
Cardiovascular effects of Cyclohexamines
Combine with Glycopyrrolate instead of Atropine
What are apneustic respirations
Breath holding, prolonged pause after inspiration
Other effects of Cyclohexamines
Catalepsy (increased muscle tone)
Open, dilated eyes
Nystagmus (mainly cats)
Ptyalism (increased salivation)
What is ptyalism & what can help this?
Anticholingergics can decrease this
How are Cyclohexamines metabolized?
Dogs- metabolized by the LIVER, then excreted
Cats- excreted by the KIDNEYS only
Ketamine general properties
Most common induction agent
Can be used for short procedures
Can squirt into the mouths of aggressive cats (takes 5-10mins)
Advantages of IV Ketamine
Faster onset and recovery
Decreased dose compared to IM
No tissue irritation
Advantages of IM ketamine
Can be used in wild/fractious animals
Longer duration of anesthesia
Duration of IV & IM Ketamine
IM= Dog: 20-30min, Cat: 30-60min.
What is the most common Ketamine combo?
Diazepam + Ketamine
(commonly mixed with tranquilizer or sedative)
What are the 3 advantages of Ketamine combos?
Increases muscle relaxation
Decreases potential for seizures
Can mix in the same syringe
Newer dissociative, very similar to Ketamine
Can be given IV, IM, or SQ (very useful for aggressive pts.)
Tiletamine common combo
Tiletamine & zolazepam
Decreases risk of seizures
Increases muscle relaxation
Porpofol general properties
(Propo-flo) -No family
Common IV induction agent
Oil in water emulsion (shake well)
Milky white but is still given IV
Cardiovascular effects of Propofol
Hypotension immediately after injection due to vasodilation
-usually short duration in healthy patients
-IV fluids will minimize this
Respiratory effects of Propofol
-transient apnea if given rapidly
How should you give Propofol?
Slowly over 20-60seconds, titrate to effect
Monitor respirations carefully for a couple min.
Once respirations are good, turn on vaporizer
Why should you pre-oxygenate with Propofol?
Flow-by or mask patient
To increase the amount of oxygen saturated with hemoglobin
Propofol drug properties
Very short acting
Wide margin of safety
Duration of Propofol
Complete recovery= 20-30min.
Limited, no preservatives
Ingredients support growth of bacteria
Use within 6 hours- Ok to extend to 24 hours
PropoFlo28 general info.
Contains benzyl alcohol to minimize bacterial growth
Lasts 28 days
Muscle myoclonus with Propofol
Seizure like muscle twitch during anesthesia- no treatment required and not common
IV injection of ____ prior to Propofol can decrease induction amount by __%
Etomidate general properties
(Amidate) -No family
Very similar to propofol
Effects of Etomidate
Minimal cardio effects
Mild respiratory depression (transient apnea)
Wide margin of safety
Rapid loss of consciousness
Rapid, smooth recovery
Adverse effects of Etomidate
IV may cause pain/irritation in people
High doses/CRI can cause RBC lysis
Muscle rigidity/myoclonus- Benzos can minimize this
Etomidate endocrine effects
Suppression of adrenal-cortical axis for 6 hours in dogs and 3 hours in cats
Single induction doses usually not a issue
Etomidate should be avoided with what patients?
Combo of opioid and tranquilizer or sedative
Used to achieve increased sedation and analgesia
When can Neuroleptanalgesics be used as a induction drug?
Only with SICK/debilitated patients
Will NOT produce unconsciousness in a young, healthy patient
Guaifenesin general properties
(Glycerol guaiacolate- GG or GGE)
Given to large animals to help induce or maintain anesthesia
Common Guaifenesin combos
Ketamine, Diazepam, Xylazine
(Triple drip: GKX)
How are liquid anesthetics delivered?
They are vaporized then delivered by carrier gas (Oxygen)
Diffusion of anesthetic gas
Gas crosses ALVEOLI then wants to travel to a place with less concentration so it goes to the BLOODSTREAM then the BRAIN becomes saturated due to high blood flow
How is the rate of diffusion of anesthetic gas controlled?
by a concentration gradient between the alveoli and bloodstream
(Goes from high to low concentration)
Concentration of gas in alveoli and blood during induction
Alveoli= increased concentration
Bloodstream= decreased concentration
How is depth of anesthesia determined?
Concentration of anesthetic in the brain
How is anesthesia maintained?
By insuring concentration of anesthetic in alveoli, blood, and brain is maintained
When recovering, how is the concentration reduced?
When the gas in the alveoli is reduced, the higher concentration in the blood will diffuse from blood stream to the alveoli
Then when the concentration of gas in the blood is less than the brain, it will diffuse from the brain, to the blood, to the alveoli
How long should animals receive 100% oxygen after the vaporizer is turned off?
5 minutes- creates a steep concentration gradient between the blood and alveoli
Precision vaporizers deliver inhalants as __ and are VOC. Meaning:
VOC= vaporizer out of circuit
What are the 6 inhalant anesthetics?
Nitrous oxide properties
Stil used in human medicine (laughing gas)
Wide margin of safety
NEVER used alone!
Nitrous oxide provides ____ & ____
Good analgesia & muscle relaxation
Color of Nitrous oxide cylinder
What 3 things does the patient breathe when using Nitrous oxide?
Respiratory effects of inhalant anesthetics
Decreased RR and Tidal Volume
-can lead to respiratory acidosis and atelectasis
Cardiovascular effects of inhalant anesthetics
-Vasodilation, Bradycardia, Hypotension, Hypothermia...etc.
-Increases heart's sensitivity to epinephrine
What are the 3 physical properties of inhalant gases?
What does MAC stand for?
Minimum Alveolar Concentration
What does vapor pressure measure?
the tendency of anesthetic to go from liquid to gas
Inhalants with high vapor pressure want to ___. Low vapor pressure gasses want to ___.
Be a gas (evaporate readily)
Be a liquid (slow evaporation)
High vapor pressure agents must use a ____ vaporizer to carefully control the % being evaporated.
2 other words for VIC & anesthetic agent used with this.
Vaporizer In Circuit
What 3 anesthetic agents need a VOC/Precision vaporizer?
What does the Solubility coefficient measure?
The solubility of an anesthetic gas in rubber tubing, blood, fat, and other tissues
What does Solubility provide info on?
SPEED of induction, depth change, and recovery
High solubility would mean that it is ____ dissolved in "stuff" and low solubility would mean it ____.
Will not dissolve easily
Inhalants with ___ solubility will move rapidly to the brain because they don't want to ____.
stay dissolved in blood, fat, etc.
(faster induction, depth changes, and recovery)
Inhalants with ___ solubility are slower, so they will ____.
be absorbed by tubing, blood, fat, tissues.
(slower induction, depth changes, and recovery)
List the 4 inhalant drugs from lowest to highest solubility. (Fastest to slowest)
Sevoflurane--fastest: low solubility
Methoxyflurane --slowest: high solubility
Inhalants with low solubility are best for what kind of induction?
Mask or chamber (faster= better)
Low solubility agents allow for ____ stage/plane changes and ____ recovery
Define Minimum Alveolar Concentration
The minimum alveolar concentration (%) of gas that produces no response to surgical stimulation in 50% of patients
What is MAC measuring & this gives an indication of the ____
The % of gas in alveoli
The ____ the MAC the ____ the gas is.
(more needed for sx)
The ____ the MAC the ____ the gas is.
(less needed for sx)
MAC x ___= light plane of anesthesia
MAC x ___= surgical plane of anesthesia
MAC x ___= deep anesthesia
List the inhalant agents from lowest to highest MAC
Methoxyflurane (most potent)
Sevoflurane (least potent)
Halothane vapor pressure & solubility
High vapor pressure
-fairly rapid induction, depth change, and recovery
-popular with equine anesthesia
Adverse effects of Halothane
Sensitizes heart to epinephrine induced arrhythmias
Increases vagal tone
**Respiratory depression- could lead to Atelectesis
___% of Halothane is metabolized by the liver and the rest is eliminated through the ____
Effects of Halothane
-Fair muscle relaxation
What is malignant hyperthermia
A rare, but often fatal disorder of thermoregulation
Results in increased temp. muscle rigidity, cardiac arrhythmias.
Can happen with any inhalant gas, but more common with Halothane
Isoflurane vapor pressure and solubility
High vapor pressure
-rapid induction, depth change, and recovery
-great for mask/chamber induction but can be irritating to mm
Isoflurane has ___ changes in depth of anesthesia (within ____ after vaporizer is changed)
Isoflurane has ___ recovery (within ____ after gas is turned off) But don't turn off vaporizer until ____.
Close to, or on last stitch
Isoflurane has a ____ MAC
Common induction % with Isoflurane=
Common maintenance %=
(Settings vary from patient to patient!)
____ has a wider margin of safety than Halothane & has little effect on the heart.
How much Isoflurane is metabolized? (%)
the rest is exhaled
Isoflurane has excellent ____ but little to no ____ post-op
Excellent muscle relaxation
Little or no analgesia post op
(give pre-emptive & post op analgesics to prevent windup)
3 Sevoflurane facts
Newest inhalant anesthetic
More expensive than Iso
Less pungent odor and less irritating to MM than Iso
Sevoflurane has ____ vapor pressure & ____ solubility
High vapor pressure & has the lowest solubility
Which gas is the fastest acting?
Sevoflurane- lowest solubility
When should you turn off your vaporizer when using Sevoflurane?
Not until surgery is COMPLETE!
Which gas has the highest MAC value?
Sevo requires ____ vaporizer settings because it is ____.
the least potent (High MAC)
How much (%) Sevo is metabolized?
the rest is exhaled
Effects of Sevo
Greater effect on the heart than Iso, but still considered safe
Moderate muscle relaxation
Little to no analgesia post-op
Smoother recovery- cognitive/motor function
Sevo has slightly more ____ than Iso
Decreased RR & Tidal Vol.
Sevo's manufacturer states that ____ & ____ return simultaneously which results in ____.
Cognitive & motor function
What is the only benefit of induction chambers?
Little physical restraint (good for feral patients)
What are the 4 disadvantages of induction chambers?
Only for small animals
Difficult to monitor patient in chamber (vitals)
No control of airway
Not a good induction method for brachys or animals with resp. or cardio. problems
What 2 things do you need when using an induction chamber?
1. Inlet for gas/oxygen
2. Outlet for scavenge
(fresh gas in, escaped gas to scavenge)
What is the induction chamber procedure?
1. Deliver 100% oxygen for about 5 min.
2. Gradually add inhalant anesthetic by 0.5% increments every 10 seconds
The induction chamber procedure uses ____ vaporizer settings for a ____ induction.
How can you tell if a patient is ready to be intubated when using a induction chamber?
Observe for loss of righting reflex
Shake the chamber or bang on the glass
What are 2 disadvantages of mask induction
Some animals resist the mask which leads to stress
Not recommended for brachys or pts. with respiratory problems (no control of airway)
When using mask induction and the animal is stressed what could happen?
Stress causes release of epinephrine which can predispose patient to cardiac arrhythmias
When does the mask induction technique work best?
When the patient is calm or sedated
Mask induction procedure
Hook up rebreathing tubing (can also use NRB)
Hook up tightest fitting mask to Y tubing
Deliver 100% oxygen
Gradually add inhalant increasing by 0.5% increments
When patient appears relaxed, turn off vaporizer, remove mask and intubate