Download anesthetic_management_in_small_animals1

BY : dr.hassan bakr
Sponsored by : orange vet. Center – vetbook
Date : 14-3-2016
1-breed
2-general animal behavior.
3-general health and physical status.
4-purpose of anesthesia .
5-familarity with the drugs .
6-current medications.
1-avilability of reversible agents . 
2-assurance of a clear air way ( tracheal tube ) 
3-carfule monitoring of anesthetized patient. 
4-preanesthetic fasting ( except in small and 
weak animals .
1- preanesthetic stage.
2- induction .

3-maintainance .
4-recovery.



Pre anesthetic considerations .

1- assessment of physical status of the patient:
A-complete case history . 
B-do a complete physical exam. 
C-review of laboratory data . 

2-formulate a specific anesthetic plan : 
A-choose the anesthetic protocol 
B-consider complication may arise during anesthesia .
C-calculate anesthetic doses. 
D-collect and prepare your equipments.

3- placing an intravenous catheter :

A- consider a complete aseptic conditions. 
B-place after premedication, prior to induction. 
C-exceptions : short procedures in healthy animals 
intractable animals . 
animals proceeds stress during I/v placement
4-gathering supplies and equipment :
A-tracheal tube. 
B-laryngeoscope. 
C-inhalation machine. 
D-monitors. 


Premedication:
1- selection of anesthetic drug is based on :
A- patient condition
B-patient general health status.
C-familarity with preanesthetic drug.
2-route of administration ( IM / S-C /IV )
COMMON PRE-ANESTHETIC MEDICATIONS :
1- ACEPROMAZINE .
2-MEDEDOMITINE .
3-XYLAZINE. 
4-DIAZIPAME. 
5-MIDAZOLAM. 



ACTIONS : 
1-CAUSE SEDATION . 
2- NO ANALGESIA. 
3- ANTI-EMITIC . 
4- LOW SIZURES THRESHLOD 
5- CAUSE HYPOTENTION IN HIGH DOSES . 
6- ASSOCIATED WITH LOWER MORTALITY IN
EQUINE ANESTHESIA .
CONTRAINDICATED IN : kidney and liver insufficiency , toxemia ,
hypovolemia and shock .



ALPHA 2 AGONIST . 
CAUSE SEDATION , ANALGESIA , MUSCLE
RELAXATION .
SIDE EFFECTS : 
CAUSE S.A BLOCK , SINUS BRADYCARDIA
HYPERTENSION THEN HYPOTENSION . 
RECDUCE CARDIAC OUTPUT . 
VOMITIMG IN CATS AND DOGS . 

REVERSAL AGENT : ATIPAMIZOL .


ALPHA 2 AGONIST . 
CAUSE SEDATION , ANALGESIA , MUSCLE
RELAXATION .
SIDE EFFECTS : 
CAUSE S.A BLOCK , SINUS 
BRADYCARDIA
HYPERTENSION THEN HYPOTENSION . 
RECDUCE CARDIAC OUTPUT . 
VOMITIMG IN CATS AND DOGS . 
REVERSAL AGENT : YHOMBINE


Decrease the dosage of I/V anesthesia . 
Anticonvulsant . 
Produce muscle relaxation . 
May cause excitation in healthy dogs and cats if
given alone .
In horses cause pronounced muscle relaxation
with mild sedation . 
Reversal agent: flumazenil


Butrophenones :
Droperidol
*azaperone
•
The same actions of acepromazine put weaker alpha 2
blocker .
Azaprone is the only approved in pigs .
•
Opioids :
•
•
Provide analgesia , decrease the anesthesia amount , good for
cardiovascular patient .
Pure agonist : morphine , hydromorphone , oxymorphone
Agonist antagonist : puprenorphine , butrophanol .
Opiates cause : bradycardia , vomiting , respiratory depression,
And may cause some excitement in healthy animal and dysphoria.
Also cause CNS depression .
Naloxane is a specific reversal agent
•
Uses of anticholinergic drugs :

Decrease salivary and respiratory secretions .
Don’t use in ruminants and horses . 
Reduce vagal mediated reflexes. 
Contraindications :

Tachycardia and tachyarrythmias .
Examples :

Atropine
glycopyrrolate .



Produce more tachycardia
Short duration of action
Penetrate BBB



Less control of salivation
cheap


Produce less tachycardia .
Long duration of action

More control of salivation
Little expensive .



Considrations during induction :

intravenous induction : 
Never inject to rapid 
Inject able induction affect the dose of inhalant anesthesia .
Most drugs are titrated dose to effect . 
Adjustment of induction dose are determined according to
the effect of pre medications. 
Induction drugs

Ketamin combinations , thiopental ,and propofol




Actions :

Sedation 
Analgesia 
Reduce nerve sensations
Side effects


Increase salivary and respiratory secreations .
Produce muscle rigidity . 
Can produce sizures alone or in high doses. 

Thiobarbiturates group 
Given slowly to produce anesthesia , dose to effect .
Has apneutic effect . 
Depress myocardial contractility . 
Prolonged recovery in grayhounds. 


it is not a barbiturate 
Rapid action 
Rapid recovery 
Hypnotic effect 
Produce no analgesia 
Cause apnea 
Cause hypotension 
can be used in maintaince to control a repid
action and rapid recovery .

We can maintain anesthesia either by injectable
drugs or inhalant drugs .
Inject able maintenance :


used for short duration procedures or when 
inhalant anesthesia is unavailable or
contraindicated
achieved by a single dose for short procedures or
small intermittent boluses doses of a drug or a
constant rate infusion in longer duration
procedures

Endotracheal intubation 
Using inhalation anesthesia machine . 
Monitoring for respiration , pulse and 
temperature,.

Post-anesthetic monitoring should continue 
until the animal can maintain sternal
recumbency or lift its head and until vital signs
are stable
External heat source should be applied to 
raise body temperature to within 1 or 2
degrees of normal body temperature
Stimulating the animal will speed recovery but
keep in mind that once the stimulation is
stopped that the animal will likely go back to
sleep
Post-operative analgesics should be 
administered as required.

Sedation may be required for the animal 
that is experiencing a rough recovery
a. acepromazine 
b. medetomidine 
Fluid therapy should be continued in the 
recovery period until the animal is
completely recovered from anesthesia.
Some disease states will require continued
fluid administration.
Bradycardia 
Tachycardia 
Hypotension 
Hypertension 
Blood loss 
Apnea 
Tachypnea 
Too Light 
Too Deep 
Remember that a heart rate defined as bradycardic is specific to a

particular animal/breed. Smaller breeds are much less tolerant of lower
heart rates while larger breeds don’t have a problem with a heart rate of
60.
The target heart rate for an animal should be its pre-anesthetic heart rate,
keeping in mind that the pre-anesthetic rate will often be elevated because
of stress/anxiety.
Possible causes. 
opioid administration 
traction on viscera 
alpha 2 agonist administration
hypothermia 
dopamine administration 
hypertension 
hypoxemia 


Treatments: 
remove cause (if possible – as in hypothermia) 
anticholinergic 
glycopyrolate 0.005 – 0.02 mg/kg IV 
atropine 0.01 – 0.02 mg/kg IV 
if administering dopamine – discontinue and wait approximately 5
minutes before administering anticholinergic

bradycardia induced by alpha 2 agonists such as Domitor can be
approached this way:
if the heart rate is just low, blood pressure is fine and there are no
arrhythmias, then you don’t really need to treat.
if arrhythmias do start to appear (second degree AV block, escape
complexes) then it may be best to administer a small amount of the
reversal (atipamezole) to bring the heart rate up rather than giving
an anticholinergi.



anticholinergic administration
hypovolemia

too light/pain during surgery
too much dobutamine/dopamine
hyperthermia

high ETCO2




Treatment: 
remove cause 
in animals with high heart rates and normal blood pressures that
are at an appropriate depth of anesthesia, it is often the case
that they have lower than normal circulating volume so that the
heart has to work harder/faster to maintain good cardiac output
and blood pressure. Often, the first response to tachycardia in
an animal that is assessed to be appropriately managed in terms
of its pain, is to administer a fluid bolus (10 ml/kg crystalloids
over 15 min) to see if an increase in volume will bring the heart
rate down.

high ETCO2 will produce sympathetic stimulation
that can cause an increase in heart rate. Solution:
ventilate
when an animal is responding to surgical

stimulation, then you should reevaluate your
approach to pain management in this animal.
Often, a supplemental dose of an opioid
(hydromorphone, fentanyl) will provide you with
the additional analgesia that is required.

Possible Causes:

hypovolemia/blood loss 
excessive anesthetic dose (usually inhalant but
can occur with injectables such as propofol)
poor myocardial contractility 
bradycardia . 

Treatments: 
generally, the first approach to dealing with hypotension in an 
animal under anesthesia is to a) reduce the dose of inhalant
anesthesia and b) administer a bolus of either crystalloids (10 ml/kg
over 15 min) or dextrans (5 ml/kg initially – can go up to 20 ml/kg in
more emergent cases) (if non-responsive to a bolus of crystalloids
or you don’t want to give any more crystalloids.
in cases where the inhalant concentration cannot be lowered but
you REALLY need to reduce it because of cardiovascular
depression, you can consider giving a supplemental dose of
narcotic (say hydromorphone = 0.05 – 0.1 mg/kg IV). This will allow
you to reduce the dose of inhalant required for anesthesia.

Possible Causes: 
too light/inadequate anesthesia 
excessive dobutamine or dopamine administration 
alpha 2 agonist administration 
excessive fluid administration 
elevated ETCO2 
Treatments: 
increase depth of anesthesia (either by increasing inhalant 
concentration or administering an additional dose of narcotic)
reduce dobutamine or dopamine administration 
ventilate if ETCO2 is elevated 
diuresis if volume overload 
Most blood loss during anesthesia occurs because
of a surgical or medical procedure. Acute blood loss
can lead to hypovolemia, hypotension and reduced
oxygen delivery. Anesthetized animals have greater
difficulty compensating for blood loss than do
conscious animals. Ongoing efforts to quantify blood
loss must be made so that adequate volume
replacement can be made. When quantifying blood
loss, keep in mind that for every 1 ml of blood lost, you
need to give 3 ml of crystalloids back to restore the
volume. This should be provided in addition to the
calculated maintenance solutions. Animals that lose
20% of their blood volume should have that volume
replaced with whole blood rather than crystalloids.

Mostly occur after induction by injectable drugs .

occurs frequently and will generally resolve on its own

In animals where you are particularly concerned about induction
apnea (i.e. animals that already have some respiratory
embarrassment), preoxygenating prior to the induction of
anesthesia will help to reduce the impact of induction apnea on
oxygen levels.
May also occur because of being either too deep under anesthesia
(or too light)



Possible causes:

too light for the procedure 
excessive ETCO2 
hyperthermia 
hypoxemia 
The most common cause of tachypnea during 
anesthesia is an inadequate depth of anesthesia
– too light (see below).
Treatments:

correct the cause

Possible causes: 
mismatch between the depth of anesthesia (inadequate) and
the level of surgical stimulation (excessive).
Usually occurs at the beginning of surgery. 
during the transfer of an animal to inhalant anesthesia 
following induction with propofol.
Treatments: 
if the animal is moving, then you need to increase the depth 
of anesthesia - giving a supplemental dose of the induction
drug is indicated.
if you just need to increase the depth slowly because you 
have noticed that the animal is responding a little to surgical
stimulation (i.e. mild increase in blood pressure, heart rate or
respiratory rate), then you can produce an increase in depth
of anesthesia by a) turning up the vaporizer and b) increasing
the fresh gas flow rate.

Possible Causes: 
mismatch between the depth of anesthesia (excessive) 
and the level of surgical stimulation (inadequate.)
too much induction drug

vaporizer set too high.

Preventing an animal from becoming too deep under

anesthesia requires close attention to the anesthetic needs
of the animal.
Before administering an injectable induction drug,

carefully evaluate how sedate the animal is following the
premedication. If it is very sedate, then you will not have
to give much induction drug.
In the same vein, if an animal is very deep after you

induce anesthesia, then you will not have to give much
inhalant initially.
Treatment: 
if the depth of anesthesia is too deep because of injectable
drugs you can either
a) reverse part or all of any reversible drugs 
b) support the animal as it metabolizes any non-reversible 
drugs.

inhaled anesthesia:

decreasing the vaporizer setting

increasing the fresh gas flow (this increases the rate at which
the gas containing the reduced concentration replaces the gas
with the “old”, higher concentration of anesthetic.

Thank you  