Download Module 2 - Angelfire

Exploration Activity
Read pages 51-118 of anesthesia text.
1. Pre-medication
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calms or sedates
reduces side effects of general anesthetics
reduces amount of general anesthetic
required
decrease pain and discomfort postoperatively
Definition
General Anesthesia
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is a state of controlled and reversible
unconsciousness characterized by a lack
of pain and memory with decreased reflex
responses to all manner of stimuli.
Boredom punctuated by panic!!!
GA Induction
2 ways to induce general anesthesia
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injection
Inhalation
Using a hammer is not an acceptable
practice
Sleep is not a form of anesthesia
Balanced Anesthesia
A technique where several different
drugs are given in order to anesthetize
an animal with a greater margin of
safety. This decreases the required
dose of each and diminishes the
possibility of toxic effects from any one
drug.
Components of GA
Pre-medication/pre-anesthetic
Induction
Maintenance
Recovery
Induction
The process by which an animal leaves
the normal conscious state and enters a
state of anesthesia is know as
anesthetic induction.
It is performed 10-20 minutes after premedication (Depending if IM or subQ)
The patient normally has a decreasing state
of consciousness during induction but there
can be an excitement phase in the middle.
Induction
Inducing agents are generally very
short acting so we generally intubate
and put the patient on gas anesthetic
as a maintenance anesthetic.
Maintenance
Achievement of a stable period of anesthetic
where surgery and other painful or involved
and precise procedures can be performed.
The patient is stable and unchanging, but is in a
state of unconsciousness that is not allowed to
become excessive or light. It is unresponsive to
stimuli like noise, pain, and light. The level or
depth of anesthesia is variable depending on the
type of surgery being done. (dental cleaning
versus bone surgery)
Monitoring respiration
Watch anterior thorax
Watch rebreathe bag
Monitor flutter valves
Check movement of abdomen
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Abdominal movement, when excessive,
may indicate difficulty breathing.
Recovery
Recovery is the return to the conscious
state after anesthetic. This achieved by
lowering the concentration of the anesthetic
to low and eventually zero amounts. It can
also be achieved by administering reversal
agents for the specific drug administered.
Drug exit from the body
Injectable drugs exit through the liver and
kidneys.
Thiobarbituates are redistributed in body fat,
for initial recovery and then slowly
metabolized by the liver and excreted through
the kidneys.
Inhalation agents are primarily excreted
through the lungs although in some there is
metabolism in the liver as well.
General Anesthetic Death
Can occur because of suppression of
cardiovascular, respiratory or
thermoregulatory function.
Must monitor the heart and respiration,
color, capillary refill time, temperature and
amount of anesthetic and oxygen and other
anesthetic gases at all times at regular
intervals (at least every 5 minutes with a
stable patient)
Big things to monitor
Heart (rate and rhythm)
Respiration (rate and depth)
Color and capillary refill time
Temperature of patient
total amount of drugs and other
substances given
Strategies to increase safety- pre-meds
Anticholinergics-increase heart rate and perfusion
Sedatives- decrease amount of anesthetic given and make
induction easier.
Management during induction–by
injections
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give minimum dose needed to achieve goals. Monitor
continuously.
Titration or “give to effect”-
means that the patient
is monitored and the administration of anesthetic drug is halted when a
certain level of anesthesia is reached.
Patient individuality
Age, breed, physical condition, pre-anesthetic
drugs given and the health of the heart,
lungs, liver, and kidneys and the animals
ability to excrete the drugs affect response to
anesthetic .
We can determine how much the patient
needs by knowing as much about them as
possible, knowing the drug we are giving very
well and titrating to effect.
Recovery room dangers
Not through all of the dangers at that time.
Can still vomit, laryngospasm, convulse,
develop hypothermia and cardiac and
respiratory arrest. Can have post op
hemorrhage or post-op shock.
Therefore we must continue to monitor
closely in the post op area.
Studies have shown this is the stage of
anesthesia where we have the highest
death rate
Classic Stages and Planes of
Anesthesia
Page 55-58 of text
Too light
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disoriented
struggling, vocalizing, paddling, chewing,
yawning (excitement phase)
reflexes present but diminished
muscle tone strong at beginning and then
diminishes.
Classical Stages and planes of Anesthesia
Adequately anesthetized
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regular respiratory pattern
gagging and swallowing reflexes diminished or absent
Palpebral reflex diminished or absent
unconscious and stable
non-responsive to pain or other stimuli
heart rate and bp normal or only slightly decreased.
Capillary refill <2 sec.
Mucous membranes pink and warm
Classic stages and planes of
anesthesia
Too deep
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spasmodic respiration or cessation of respiration
significantly decreased heart rate, blood
pressure
Pale and cold mucous membranes
capillary refill delayed
total skeletal muscle relaxation, no jaw tone
Dog spay exploration activity
Page 10 of course pack
1. Reception history
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pre-starve? For how long?
How is her recent health? Any health
history?
Family history of anesthetic problems?
Other patient signalment stats
Others?
Pre-anesthetic exam
Temperature
heart rate and quality of pulse and rhythm
respiration rate and quality
capillary refill and mucous membrane color
attitude and demeanor of patient
pre-anesthetic blood panel
Premedication
Acepromazine
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11.3kg X 0.05mg/kg = 0.565mg
.565 mg/10mg/ml =.0565 ml = .06 ml.
How do you draw up such a small amount
Atropine
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11.3 kg x .02 mg/kg = .226 mg
.226 mg/.5 mg/ml = .452 ml = .45 ml
Net effects of ace and
atropine
Mild sedation
slight increase in heat rate and bp
makes her more susceptible to other
anesthetic drugs
wait 6 - 10 minutes after administration
IM of pre-anesthetic agent before giving
anesthetic.
Anesthetic induction
Goes from fully awake and aware to a drowsier stage.
Becomes disoriented and can become excited. May
vocalize and struggle.
Progresses to paddling and whining
muscle tone decreases over time
heart rate will increase then decrease to a lower stable
level.
Muscle tone decreases over time.
Pain sensation decreases over time.
Responses to surgery
Respiration will increase with stimulation
heart rate increases and bp and pulse also
Major increase in all parameters with first cut
or manipulation of the abdominal organs if too
light a plane of anesthesia.
Mucous membrane color should remain pink
CRT should remain <2 seconds
Practical Application Activity
parameter
assessed
respiration
H/R pulse
CRT
MM color
Response to sx
too light
fast
fast
good
pink
adequate
steady regular good
pink
too deep
slow
pale
slow
slow
Induction with inhalation
agents (pages 62-64)
Reception presentation- an example
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This is Fluffy Ness, a Birman cat, here for a
spay&declaw. She has been pre-starved for 12
hrs and no water for 3 hours. Last vaccines
were in October last year and September before
that. She is not in heat and she has never had
kittens. She is strictly an indoor cat. She has
had a string removed from under her tongue
with anesthetic (with no complications using
isoflurane) when she was a kitten but has had
no other health problems.
Fitting mask
Fits tight over face without leakage
(should cover entire mouth)
minimize dead space (space between
nose and inlet hose)
avoid traumatizing eyes and nose
do not put pressure on trachea
Method of induction of cat
Restrain by wrapping in a large towel or in a cat
bag
short end close to handler & fold large end over
the body and then put weight on it with the neck
firmly restrained.
30 secs of O2
10 sec ea of 1,2 ,3,4 % gas (halothane or
isoflurane)
monitor until cat becomes lightly anesthetized and
then unwrap.
Turn down to 3 % as it gets deeper (pedal reflex
still present) and 2% when at a surgical plane (no
pain response)
Mask induction
Job of assistant is to monitor level of
anesthetic depth and communicate it to the
other members of the anesthetic team.
Has a very noticeable excitement phase
with gas induction, not seen with thiopental
or propofol.
Restrainer unwraps cat after excitement
phase is finished.
Unwrapping the cat
1st step in deciding to unwrap based on muscle resistance.
Start by laying cat in lateral, if it is still awake it will try and
right itself.
Reach under the towel and grab the cats hind legs. Pull on
the legs to feel the level of muscle tone.
May unwrap front legs if little resistance is felt.
If still moving, grab front legs and restrain in hand with
finger between legs.
It is important to get the cat unwrapped ASAP to be able
to visually evaluate the cat and test for muscle tone, pedal
reflex, and observe respiration.
Communication between
partners
Restrainer should continually update the
anesthetist about the patients condition and
level of anesthesia, so that the anesthetic
can be turned down from 4% before the
patient gets too deep.
Should be at 3% when no longer struggling.
Monitor pedal reflex and patient should be
down to 2% when pedal is absent.
Important Habits to develop
Report cats condition out loud to all concerned.
It is better to be slightly light than too deep
You cannot turn the anesthetic down
when the animal has died or gone into
arrest and expect a favorable outcome.
Once cat is deep enough, move on to the 5 pt.
Monitoring process. Check and then prep for
surgery. We should keep our patient down for as
little time as possible. Don’t dawdle and keep
pressing forward.
Time is trauma
Hints
Don’t be slow. Some patients go down very
quickly. Change levels of anesthetic as soon as
reflex is absent.
Turn down too soon rather than too late. Restrain
adequately until the muscle tone is diminished.
(Halothane with cats that scream)
Can turn down to maintenance level before fully at
surgical plane. The patient has time to deepen
during surgical prep.
Move on as soon as an animal reaches the surgical
plane of anesthesia.
Time is trauma!!
Masking down small dogs
Mostly like cat
often don’t need to towel restrain. No sharp
claws.
Restrain in a conventional hold. Use several
people for larger, stronger dogs.
Use the same reflexes.(muscle tone,
palpebral, pedal)
We routinely intubate dogs, thus always
assess jaw tone. It will not disappear as
rapidly when induced with thiopental.
Masking down small dogs
When jaw is slack, place dog in sternal with
hind legs in frog position. Hold head with
mouth open for anesthetist to intubate.
The anesthetist, who is prepared in advance,
removes the mask, intubates, then reattaches
the anesthetic vaporizer to the tube.
The vaporizer setting is based on the animals
reaction to the tubing process. Turn it up if it
is chewing and leave at maintenance if stable.
If chewing with tube in, firmly restrain the jaw
INDUCTION WITH THIOPENTAL
Page 59-60 of text book
Advantage- very rapid progress to surgical
plane of anesthesia. Mostly circumvents
the excitement phase that we see with
mask induction with a gas anesthetic.
A standard dose is drawn up in a syringe,
then administered IV as needed to allow
endotracheal intubation and maintenance
on gas anesthetic.
Induction with Thiopental
Can be used by itself for minor and quick
procedures, but should not be used for
extended procedures because the
accumulation of the drug in the body may
result in very prolonged recovery.
Examples of minor procedures may be xrays, porcupine quills, endoscopy, or skin
biopsy.
Induction with thiopental
Normally, patient is pre-medicated with a
“cocktail” like BAG. This allows for a lower dose of
the inducing agent and a smoother induction with
greater safety. Butorphenol, acepromazine,
glycopyrollate.
Standard dose is calculated based on weight (1018 mg/kg) and then 1/2 that dose is injected
rapidly IV over a period of about 10 seconds to
get to a surgical plane of anesthesia without much
excitement.
Coursepack calculations
10mg/kg x 28.4kg = 284 mg / 40mg/ml=7.1ml
18mg/kg x 28.4kg = 511 mg / 40 mg/ml=12.8ml
Induction with thiopental
If patient is deep enough, the procedure is
performed without any further anesthetic if
it is minor and quick.
If surgery is more involved, the patient is
intubated and placed on an anesthetic gas
to maintain anesthetic more or less
indefinitely.
Induction with Thiopental
Thiopental is an irritating chemical with a very
alkaline pH. (pH>9) If it goes perivascularly it will
cause an inflammatory reaction.
It is useful to give through a preset catheter and
administer the lowest concentration that can be
handled easily. (2.5% for dogs and cats, 10% for
large animals).
If it does go perivascular, infiltrate the area with
an equal amount of lidocaine which is acidic and it
will neutralize the high pH solution. The follow up
with 10x the volume of isotonic saline as a diluent.
Thiopental math
We normally discuss doses in gm %.
This means that 2% is 2gm thiopental
/100ml sterile water or 20mg/ml.
5% is 5gm/100ml or 50 mg/ml
How do you make a 4% solution if you
have a vial with 1 gm.of thiopental.
Answer: add 25ml sterile water to 1
gm of thiopental.
Thiopental Induction Apnea
Apnea means lack of breathing.
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Often patient will stop breathing immediately after
induction.
Very important to monitor closely at this time.
Watch color, CRT, look at chest, auscult with a
stethoscope.
If patient won’t breath- the NAIT way
 extend hind legs fully, this stretches the diaphragm.
 Feel chest for heart beat, give a gentle squeeze.
 Check color/crt and pull on tongue.
Thiopental Induction Apnea
If not breathing, do again.
If still not breathing, intubate and inflate the
patients lungs at a regular interval.
One theory is that we change the body’s
normal reflexes with anesthetic. As we get
deeper under anesthetic our body no longer
responds to lack of O2 to stimulate the
breathing but responds to an increase in CO2
to stimulate breathing.
Thiopental Induction Apnea
At induction we go from O2 deprivation driving
respiration to CO2 buildup driving respiration.
As an anaesthetic proceeds and thiopental is
absorbed, the animal reverts back to O2 drive.
This impacts on how much the animal breathes at
the beginning, middle and end of the procedure.
This is a very important reason for the need for
constant monitoring.
The animals reflexes and needs will
actually change over time.
Administration of Thiopental
Calculate the dose for the patient
try and use the minimal dose to achieve your
procedural goal.
Range is 10-18 mg/ kg.
Younger animals require a higher dose.
Smaller animals require a higher dose.
Underweight animals require a lower dose or possibly
a different drug.
Don’t give to animals with liver disease because after
redistribution in body fat, it is ultimately broken down
in the liver.
Examples
Don’t use on greyhounds.
Chance will remain anesthetized for 6-8 hours with
barbiturates while Daisy is under for 20 minutes.
Draw up a dose of 18mg/kg for a 10 kg. hyper
terrier and draw up a dose of 10 mg/kg for a 9
year old German Shepherd.
Give 1/2 iv and then wait up to 30 seconds to
evaluate the effects. If not enough give another
1/2 of what’s left and wait another 30 seconds.
Do this until the animal is deep enough or you run
out of drugs.
Examples
REMEMBER!!
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Every patient is different and you DOSE TO
EFFECT.
Age, size, % body fat, and health status all
affect the animals reaction to the drugs.
There are more unusual drug reactions to
anesthetic drugs than any other drug.
Always be prepared for the worst case scenario.
NAITS five things
Heart rate and character
respiration rate and character
MM color/CRT/ temperature
02 flow and concentration of anesthetic
gas
fluid admin rate and total fluids
remember that other facilities may do things
differently, but it really is only a variation of this
program.
Other useful things are jaw tone, palpebral reflex and
eye position.
Endotracheal intubation
Pages 65-75 of text book
We will practice this technique at the SPCA
in February.
Definition:
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placement of a breathing tube into the trachea
to facilitate the administration of anesthetic gas
and O2 and by passing the nasal passages, oral
cavity and pharynx.
Endotracheal Intubation
Advantages:
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more efficient delivery of anesthetic gas
and 02 to the patient. Reduces usage of both
and minimizes the atmospheric contamination
from the administered product.
Reduces dead space within respiratory
passage, ensuring more 02 exchange at the
alveoli.
Enables assistance of respiration by means
of a reservoir bag, a respirator or direct CPR.
Endotracheal Intubation
Advantages
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inflated cuffs reduce the the risk of
aspiration of vomitus, blood, saliva or other
damaging substances
can leave in until the animal wakes up
enough to have a swallowing reflex and is no
longer in great danger of aspirating
Disadvantages of Intubation
Vagus nerve stimulation resulting in
increased parasympathetic tone.
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Causes bradycardia (decreased Heart
rate), hypotension(low blood pressure),
and dysrhythmias.
Very rarely this results in cardiac arrest.
Atropine and glycopyrollate pre-medication
helps prevent this parasympathetic
stimulation.
Disadvantages of Intubation
Some breed are difficult to intubate like
brachycephalic breeds. They probably benefit the
most from it though because the soft palate can
obstruct the larynx.
Rough handling can result in damage to the
larynx, pharynx, soft palate, or epiglottis.
Cats are especially hard to intubate because of
laryngospasm. Can be so severe that it leads to
asphyxiation or conversely, you may not be able to
remove the tube after surgery.
People are as well. We use cats to teach human
intubation.
Disadvantages of intubation
Some large animals and some lab animals
must be tubed blindly which can be difficult.
If endotracheal tube is inserted too far it
may enter a bronchus and effectively limit
oxygenation to one lung. This can be
avoided by measuring from the canine to
the thoracic inlet.
Have too much dead space if tube sticks
way out of mouth. Cut tube shorter in this
case.
Disadvantages of intubation
Pressure necrosis from over inflation of the cuff.
Tube blocked by saliva, mucous, blood or foreign
material.
Tube can become kinked.
Tube can be placed in esophagus
Patient can wake up and chew off the tube and
inhale the bottom half. Usually happens if surgical
team becomes distracted. I have seen this
happen and the vet had to do a tracheotomy!
Disadvantages of intubation
Diseases can be spread from one patient to
the next by the endotracheal tube.
Always clean and disinfect tubes between
patients.
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Use product that doesn’t damage rubber or
silicone or plastic.
 Hibitane is best
Endotracheal Intubation
Procedure
Get all materials ready beforehand.
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Include several different sizes of tubes
check for holes in the tube, leaking cuffs, loose
connectors etc.
length of tube is from incisor to thoracic inlet
and place tie at appropriate place.
approximate size is determined by palpating the
trachea.
Lubricate tube with k-y or other water soluble
lubricant. Don’t over use lubricant.
Endotracheal Intubation
Procedure
Spray larynx with local anesthetic (especially
cats) and then wait one to two minutes for
it to take effect.
At appropriate plane of anesthesia, place
animal in sternal and open mouth while
raising the head and extending the neck in
a straight line.
Hold the lips dorsally and pull the jaw
ventrally with the tongue.
Endotracheal Intubation
Procedure
Open mouth wide enough to see epiglottis.
If a laryngoscope is used, use the blade to
pull the tip of the epiglottis rostrally and
push the base of the tongue ventral.
Can also blind intubate or digitally intubate
if it is impossible to visualize the epiglottis.
Insert the tube into the trachea through the
vocal folds and or aretynoid cartilages
where the opening is largest.
Endotracheal Intubation
Procedure
Inserting tube can be difficult because the
tube can stimulate swallow, cough,
laryngospasm etc.
Also normal breathing opens and closes the
glottis, so timing becomes critical in the
placement of the tube.
If resistance is encountered, gently rotate the
tube into the trachea or remove and replace
with a smaller diameter tube.
Endotracheal Intubation
Procedure
Small diameter tubes may require a stylette.
Once placed, the anesthetist should confirm
the position of the tube by:
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observing appropriate movement of the reservoir bag
on the anesthetic machine.
Visualize placement of the tube
palpate placement externally
visualize a cough reflex with tube placement.
Moving a tuft of hair placed at the tube opening.
Observe movement of the valves in the anesthetic
machine.
Vocalization means tube is not in trachea!
Endotracheal Intubation
Procedure
Tie the tube in place.
Inflate the cuff of the tube and check for
leakage. The cuff should not allow leakage
and not be so tight as to cause pressure
necrosis.
Check for leakage by pressing on the
reservoir bag and listen for air leakage at
the glottis.
Maintainance of GA
Pages 75-110 of text
2 important tasks
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monitor the animals vital signs closely
 practically it means checking an animal every 3-5 min
 more often if unstable or very high risk.
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maintain animal at appropriate anesthetic depth
 too light and it feels pain- turn up machine
 too deep and it dies or has permanent organ
damage. Turn down machine, bag with pure 02
before it happens.
Nait 5 things
Parameter
Heart Rate
Critical value varies
with patient
120-200
Resp Rate
12-32
Capillary Refill
PW<2
Anesthetic
2%
Oxygen
Never< 1 L/min
Vital signs
Heart rate and rhythm
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minimal acceptable rate are 70 (dog) and 100
(cat)
should correlate heart beat with pulse or other
measure of blood pressure.
Useful to use esophageal stethoscope
Reach under drape with stethoscope, not over
blood pressure
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rough estimate with capillary refill time
normal CRT is <2 sec.
Indirectly measured with doppler
direct measurement possible with indwelling catheter and pressure
measurement device.
Vital Signs
Blood pressure
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normal systolic 110-160 mm Hg.
Normal diastolic 60-100 mm Hg.
Hypotension is decreased bp
hypertension is increased bp
do not see a decrease in CRT until systolic
bp<70-80 mm HG.
Vital Signs
Monitoring BP
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indirect with sphygmomanometer
 use inflatable cuff to compress an artery
 if pressure greater than systolic no blood flow
 blood flow starts when pressure in cuff=systolic pr.
 When cuff pressure> diastolic pr blood flow
disrupted
 blood flow normal when cuff pressure= diastolic pr.
 We can measure these disturbances in flow using
stethoscope, doppler or oscillometer.
Vital Signs
Monitoring Blood Pressure
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directly
 central venous pressure lets anesthetist know how
well blood is returning to the heart and the ability of
the heart to receive and pump blood.
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Done by inserting long catheter into jugular so that
catheter tip is close to r. atrium and then connected to
water manometer.
Useful for R heart failure and monitoring for over hydration
of animals receiving IV fluids.
Normal 12-15cm H20
Vital Signs
Monitoring Blood Pressure
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capillary refill time
 reflects the perfusion of tissue with blood
 can observe a normal CRT in a very recently
euthanized animal. Not infallible.
 Prolonged CRT may indicate hypotension from
excessive anesthetic depth or circulatory shock.
 If crt> 2 sec. Systolic bp < 80 mm Hg
 if crt absent systolic bp < 50 mm Hg. ( in this
circumstance the mm’s are cold and colorless)
 Measure on ears, pads, gums, vulva, rectum, skin
with no pigment
Vital Signs
Mucous Membrane color
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can indicate blood loss or signs of shock
should estimate blood loss during surgery
 one soaked sponge holds 5-6 ml blood
 may double amount to take into account
unmeasureable amounts.
 Healthy animal can lose 15% (13 ml/kg for average
dog and cat)
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Make sure fluids actually flowing during whole
surgery, can stop spontaneously or may speed
up if patient is repositioned.
Vital Signs
Respiration (rate and depth)
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usually less than when awake
rate of <8 resp.’s / min is a concern.
Depth also decreases with depth of anesthesia.
If not breathing deeply can lead to pulmonary
atelectasis (alveolar collapse).
Can reverse atelectasis by gentle pressure on rebreathing bag (called bagging) or 15-20 cm of water
pressure. Some anesthetists do this routinely every 5
minutes.
Audio patient monitor useful here
 Other noises and movements a problem
Vital Signs
Respiration
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Hypoventilation- sign of too deep
Hyperventilation or tachypnea- sign too shallow.
Labored or difficult breathing may indicate
obstruction of airway.
Rocking boat respiration is a sign of excessive
anesthetic depth.
Auscultation important
Don’t let hoses and ET tube get kinked
Vital Signs
Blood Gases
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is best evaluation true respiratory efficiency
hard to do directly and is rarely done in regular
circumstances.
Pa 02 almost always high because on 100% 02
Pa C02 elevated because respiratory depression from
anesthetic.
Leads to respiratory acidosis pH drops to as low as 7.2
from a Normal 7.45
can measure blood gases indirectly with pulse oximeter
 Shows arterial oxygen saturation
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Should always be greater than 90%
Always look at machine when checking oxygen because
the tank can run out and you can miss it.
Vital Signs
Temp loss is greatest in first 20 minutes of
anesthesia.
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Result of:
 clipping, scrubbing, alcohol rinse
 less heat generation under anesthesia (shivering
absent)
 decreased metabolic rate
 exposure of viscera to room air and cooling
 vasodilatation from drugs causes increased heat loss
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hypothermia causes prolonged recovery from
anesthetic.
Vital Signs
Hypothermia
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slows rate of metabolism in the liver slowing the
excretion of anesthetic agents
shivering during recovery increases 02 requirements
during recovery and can result in hypoxia.
Measure temp every 30 minutes
Prevent with heating pad or other heat source.
Wrap patient in blanket
Warm the IV fluids
Keep OR warm
Hyperthermia very rarely seen
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malignant hyperthermia seen in dogs and pigs
treat with sodium dantrolene and cooling animal
Vital Signs
Reflexes
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Palpebral-blink when touches on eye lid
Swallowing-pull tongue
Pedal- pinch toes
Ear flick- ears flick when tickling ear hair.
Corneal- touch cornea and get a blink.
Laryngeal- cough when et tube touches larynx
Muscle tone- esp., jaw tone, but also leg and
trunk
Vital Signs
Eye position and pupil size:


considerable variation amongst individuals
Eye
 central early stages of anesthesia
 rolls inward (eccentric) at surgical planes
 central in deep levels
 ketamine doesn’t do this. Very noticeable with
halothane.
Vital Signs
Eye position and pupil size

pupil
 dilated at stage II, constricted at light levels
and more dilated at increasing depths
 light reflex diminishes with depth
 dilated central pupils, non-responsive to light
indicate a very dangerously deep patient.
 Atropine causes pupillary dilation.
Vital Signs
Salivary and Lacrimal Secretions


decrease with anesthetic depth
should use some kind of opthalmic ointment with
prolonged and deep anesthesia.
Heart and Respiratory Rates

tend to decrease with depth but are not infallible. For
example heart rate increases with decreasing bp which
may be the result of excessive anesthetic depth.
Vital Signs
Response to Surgical Stimulation



increased heart rate and bp related to painful
stimulation.
Respiration rate and depth increases with
surgical stimulation if animal is too light.
No response to surgical stimulation may indicate
a patient which is too deep.
Vital Signs
Judging Anesthetic Depth





use as many parameters as possible to gauge
lots of individual variation to specific parameters.
Parameters vary from drug to drug
parameters vary with depth. Eg) eye with
halothane.
Rule of thumb- If unsure of anesthetic depth, turn
down vaporizer until you can get a handle on the
patient
Recording Information during Anesthesia
Complete and accurate records are a legal
requirement.
For example- log book containing date,
client, patient, physical status pre-op
description of the procedure and anesthetic
protocol and outcome.
Should be recorded with patient as well.
Gives statistical information that is useful to
the vet and practice.
Patient Positioning
Support patient during induction so that the head
does not hit the table as induction occurs.
Support entire spine and neck when transporting
small animal to surgery, Use trolley for large.
Disconnect endotracheal tube before turning a
tubed patient over. Whenever possible, turn on
sternum rather that on spine. (prevents torsion)
Confirm placement of tube before positioning a
patient in an awkward position.
Position hoses from anesthetic machine so there is
no tension on the endotracheal tube.
Make animals position as normal as possible.
Patient Positioning
Patient comfort whenever possible
Sternal while inducing.
Protect head especially during induction.
Ropes should be tied appropriately.
Heavy drapes and instruments must not compress the
patients chest.
Tilting the table can result in respiratory depression if
the head is lower than the body.
Do not kink the neck excessively
Heavy instruments on body can impair respiration
If one lung is bad, position with normal lung up
Transferring to another
anesthetic machine
1) Turn off anesthetic and let breathe air for
2)
3)
4)
5)
one or two breaths.
Disconnect and immediately turn of
oxygen
Carry patient to next machine.
Turn on oxygen and then attach patient.
Turn anesthetic to appropriate level.
Anesthetic recovery.
Pages 110-115 of text
Defined as the time taken to return to
sternal recumbancy after discontinuation of
anesthetic administration.
Affected by:




length of anesthetic
condition of patient
type and route of administration of anesthetic.
Patients temperature.
Stages of Anesthetic Recovery
Try and turn off anesthetic so patient is
coming light as the final stitch is done.
Don’t turn off oxygen until the patient has
had several minutes of oxygen or until it is
waking up. Wake up faster with isoflurane.
Gradual process back through the same stages of
induction in reverse.






Heart and respiration rates increase
eye rotates to central
reflex responses return gradually eg. pedal
shivering
swallow, chew, lick
return to consciousness
Anesthetists role in recovery.
Don’t walk away when patient on table. Can fall
off.
Remove ET tube as soon as jaw moves. Earlier in
cats.
May place on floor or in monitored cage after ET
tube out and finish paper work, clean up etc.
If patient won’t wake up stimulate reticular
activation center in brain.
Fully arouse patient. Should not leave it totally
alone until it can walk or stand.
Indicates that the anesthetic is gone and you can
safely leave it alone.
Anesthetists role in recovery.
Death can still occur in this period.

Some people say this is the most dangerous
period.
Should watch animal as much as possible


Check mental alertness and response
If you talk to the animal and it looks at you, it
is a good sign.
Emergency kit should be readily available
and ready to use.
Drugs should not be out of date and
administration apparatus should be available.
Anesthetists Role in recovery
Monitoring




continue doing vitals every 5 minutes during
recovery.
Observation from across the room is not
adequate.
Delayed return to consciousness should not be
ignored.
Possible complications include:
 shock, hemorrhage, hypoglycemia, hypothermia,
vomiting, seizures, laryngospasm, and dyspnea.
Recovery Period
Give 02 for several minutes after
administration of anesthetic is discontinued.





High flow rate for up to 5 minutes or until animal
swallows.
Flushes anesthetic out of system faster and speeds up
recovery.
It also allows expired waste gas to be scavenged rather
than breathed out to room air.
Periodic bagging re-inflates collapsed alveoli and
increases rate of anesthetic gas removal.
Can give 02 with mask or canula after animal wakes up
if it is felt to be necessary
Recovery Period
Recover in sternal with neck extended
to maintain a patent airway.
Remove fluid, blood and mucous from
pharynx with suction or a gauze if
necessary before you extubate.
Recovery Period
Extubation:







remove when arousal is occurring
swallowing is the usual first sign
voluntary limb or head movement another sign
leave brachycephalic breeds longer, and be prepared to
re-intubate if necessary
don’t leave tube in for extended time in cats because of
laryngospasm.
Always untie gauze and deflate cuff before extubation.
May leave cuff partially inflated if there is debris in the
pharynx (after a dental for eg.)
Recovery Period
Stimulation of the patient can hasten
recovery in some instances.

Talk, pinch toes, open mouth, move limbs or
trunk, rub the chest all help.
 All work by increasing input into the reticular
activation center of brain which is area of brain
responsible for consciousness.


Turn over every 10-15 minutes to prevent blood
pooling.(hypostatic congestion)
deep chested animals are at a minor risk to
gastric torsion if turned any way but sternally.
Recovery Period
Reassuring the patient is important because
they are disoriented and have no means to
understand what has happened.
The excitement phase that occurred in
induction can occur in reverse with recovery.
Make sure all procedures are finished, like
bandaging, removal of ties, etc.
Recovery Period
Leave catheter in place until recovery is
complete whenever possible.
Post-op analgesics are best given before the
animal experiences the pain.
If that is the case, less drugs are needed
and there is less likelihood of recovery
injury related to struggling.
Post op analgesics can slow animals return
to sternal, especially if using narcotics.
Recovery Period
Nursing care should include :





heat for all hypothermic animals
gradual re-warming is preferred
ample bedding
never leave alone unless in a secure cage.
No food or water unless fully recovered.
Recovery period
Prevent Patient self-injury during period of
excitement esp with pentobarb and other
injectable inductions.
Sometimes see a stormy recovery.
This can interfere with proper healing and may
result in further trauma over and above what
happened surgically.
Anesthetists duty is not done until patient is fully
and calmly awake and standing.
No food and water until fully recovered. If worried
about blood sugar, give IV dextrose.
Maintenance of Anesthesia
5 thing check at NAIT
 Heart rate
 respiration rate
 color, crt
 Anesth/02
 iv fluid rate
70 dog / 100 cat
<8 dog and cat
pink,warm,<2sec
2% 1.5l
10ml/kg/hr