INDUCTION AND MAINTENANCE OF ANESTHESIA IN FIELD CONDITION in animals

1. TOPIC OF PRESENTATION
INDUCTION AND
MAINTANANCEOF
ANESTHESIA IN FIELD
CONDITION

2. OUT LINES
• Anesthesia
• Types of Anesthesia
• Components of general anesthesia
• Stages and planes of anesthesia
• Types of general anesthetics
• Side effects of anesthesia
• Field common anesthetics
• Type of surgery and anesthetic protocol used

3. Anesthesia
• Anesthesia is a state of controlled , temporary
loss of sensation or awareness that is induced
for medical purposes . It may include
analgesia , paralysis, amnesia or
unconsciousness .
• A patient under the effects of anesthetic drugs
is referred to as being anesthetize .

4. Types of anesthesia
• There are three main types of anesthesia .
1 : Local anesthesia
2 : Regional anesthesia
3 : General anesthesia

5. Local Anesthesia
• Local anesthesia is any technique to induce
the absence of sensation in a specific part of
the body , generally for the aim of including
local analgesia ( local anesthetic nerve block ),
that is , local insensitive to pain , although
other local senses may be affected as well .
• Clinical local anesthetics belongs to one of two
classes ( 1: Aminoamide local anesthetics , 2:
aminoester local anesthetics )

6. Common local anesthetics used
• Two classes of local anesthetics used .
1 : AMINO AMIDES : It include lidocaine ,
mepivacaine , prilocaine , bupivacaine ,
etidocaine , ropivacaine and levobupicvacaine.
2 : AMINO ERSTERS : It includes cocaine ,
procaine , tetracaine , chloroprocaine , and
benzocaine .

7. Uses of local anesthesia
• We used local anesthesia more commonly in
large animals for different purposes .
• Like different nerves block of head region (
cornual nerve , mental nerve , maxillary nerve ,
arecuolopulpebral nerve , retrobulbar nerve etc
… )
• Nerve block of foot region ( palmar nerve , digital
nerve etc …)
• In cattle use for C- section procedure to block
nerves in flank region and also used for any
surgical procedure in udder etc …

8. Regional anesthesia
• Regional anesthesia is the use of local
anesthetics to block sensation of pain from a
large area of the body , such as an feet or tail
or the abdomen .
• Regional anesthesia allows a procedure to be
done on a region of the body without your
being unconscious .
• E.g inverted L-block , O ring block , teat block ,
epidueral block etc…

9. General anesthesia
• General anesthesia is a state of controlled and
reversible unconsciousness achieved through the
use of injectable or inhaled drugs characterized
by the absence of pain perception , memory
motor response to stimuli or reflex responses .
Ideally this state is achieved without significantly
affecting the patients vital systems particularly
respiration and circulation . Safe anesthesia is
achieved through appropriate selection of drugs ,
careful administration , and constant monitoring .

10. Components of general anesthesia
• General anesthesia is achieved through the
use of techniques and agents chosen by the
veterinarian that is called the anesthetic
protocol . Patient may be anesthetize by one
drug or several agents used in combination in
a technique called balanced anesthesia . Any
anesthetic procedure may be divided into the
following components pre anesthesia ,
induction , maintenance and recovery .

11. Preanesthesia
• A period immediately preceding anesthesia in which
patient data are collected , the patient is fasted and
adequate hydration ensured , and pre anesthetic drugs are
administered .
• Pre anesthetic drugs are classified as :
1 : Anticholenergic ( atropine sulphate , glycopyrolate )
2 : Tranquilizetrs / Sedatives
a : Phenothiazines ( acepromazine ,chlorpromazine)
b : Benzodiazepines ( dizepam , midazolam , lorazepam)
c : Alpha 2 antagonist ( xylazine , medetomidine, detomedine )
3 : Opiods ( morphine , oxomorphine , fentanyl , naloxane)

12. Induction
• The process by which an animal leaves the
normal conscious state and enter an unconscious
state is known as induction . The minimum time
is 10 minutes for I/m rout and 20 minutes for S/C
rout . Initially the animal may show signs of
incoordination or excitement , followed by
progressive relaxation and unconsciousness .
Ideally , excitement and struggling should be
avoided during induction , because this is
unpleasent for the patient and predisposes the
animal to cardiac arrhytmias and erivascular drug
injection .

13. Maintenance
• After the induction period , the animal enters
the maintenance period , during which
sufficient amount anesthetic is required to
keep the patient at an appropriate depth of
anesthesia . Surgery and other procedures are
commonly performed during this period .
Close monitoring is essential throughout this
period .

14. Recovery
• The maintenance period ends and recovery begins when the
concentration of anesthetic in the brain begins to decrease . The
elimination of drug from body differs amongs drugs .
• Most injectable drugs are removed from the blood by liver and
undergo metabolism by liver enzymes . The metabolites are
excreated by the urinary system . Some drugs are not undergo
metabolism and are excreted unchanged by kidneys e.g ketamine
in cats .
• Inhilation agents are eliminated mainly through the respiratory
tract . Anesthetic molecules leave the brain , entering first the blood
and than alveoli of the lungs and exhaled .
• Recovery from anesthesia is almost the reverse of the induction
process . Reflex activity , muscle tone , and sensitivity to pain are
regained as conciousness returns .

15. Stages and Planes of anesthesia
• During the course of general anesthesia , the animal passes through
a series of anesthetic stages and planes roughly correlated with
changes in anesthetic depth .
• STAGE 1 (stage of voluntary excitement)
• Immediately after or during the administration of an inhilation or
injectable agent , the animal enters the initial stage of anesthesia
stage 1 . Animals are conscious but disoriented and show reduced
sensitivity to pain . Respiration and heart rate are normal or
increased , and all reflexes are present . The patient is still awake
and may show stuggling , urination , defecation and signs of fear
and anxiety .

16. Stage 2(stage of involuntary excietment)
• Stage 2 begins with the loss of consciousness . All reflexes are still
present and animal is able to chew and swallow . Yawing is common
. The pupil are dilated but will constrict in response to intense light .
As the higher centers of the brain release voluntary control of the
body functions , the animal may exhibit involuntary excitement in
the form of rapid movement of the limbs , vocalization and
struggling . Breathing may be irregular or the animal may appear to
be holding the breath . The animal appears to be fighting the
anesthesia . This stage is unpleasent for the animal and potentially
hazardious to hospital personnel . Also there is a risk of epinephrine
release and the possibility of cardiac arryhthmias or arrest .
Premedicated animals that are rapidly induced with an injectable
anesthetic usually pass directly from stage 1 to stage3. stage 2 ends
when the animal show signs of muscle relaxation , slower
respiratory rate and decreased reflex activity.

17. Stage 3( stage of surgical anesthesia)
• This stage is subdivided into four plans .
PLANE 1
The respiratory pattern become regular , and involuntary
limbs movement cease . The eyeballs start to rotate
ventrally , the pupil may become partially constricted , and
the pupillary response to bright light is diminished . The
swallowing reflex may be depressed so endotracheal may
be passed . Palpebral reflex is present however , response is
less than stage2 . although animal appears unconscious ,
but patient will not tolerate surgical procedure at this light
plane of anesthesia and will move . Increased respiratory
and heart rates but descending .

18. Plane 2
• Animal are generally consider to be at medium depth
of anesthesia , suitable for most surgical procedures
especially minor procedures . Surgical stimulation may
slightly increase heart rate and respiratory rates , but
the patient usually remains unconscious and immobile
. Pupil slightly dilated and the pupillary light response
is sluggish . The respirations are regular but shallow ,
with the respiratory rate between 12 to 16 breaths per
minute in dogs and slightly higher in cats . Mild
decrease in heart rate and blood pressure . The skeletal
muscles tone becomes more relaxed and many of the
normal protective reflexes e.g pedal, layrngeal , and
palpebral are lost .

19. Plane 3
• The patient appears to be deeply anesthetized .
Significant depression of circulation and respiration is
present . Respiratory rate is less than 12 breathes per
minute and respiration is shallow . Heart rate is notably
reduced even in response to surgical stimuli . Pulse
streanght may be reduced because of fall in blood
pressure . The CRT may be increased to 1.5 to 2
seconds . Pupillary light reflex is poor . Pupil
moderately dilated . Eyeball become central . Reflex
activity is often totally absent . Profound skeletal
muscle relaxation and loss of jaw tone . Major and
painful surgeries can be performed in this stage .

20. Plane 4
• This can be recognized by a rocking respiration in which
the abdominal muscles are increasingly responsible for
ventilation while the thoracic muscles become less
active . The overall effect is a decrease in effective
ventilation . Fully dilated pupils and absece of pupillary
light reflex . Dry eyes due to absence of lacrimal
secretions . Muscle become flaccid . Marked
depression of cardiovascular as evident from drop in
heart rate and blood pressure , accompained by pale
mucus membranes and prolong CRT . The patient in
the plane is so deeply anesthetized for safety and is in
danger of respiratory and cardiac arrest .

21. Stage 4 (stage of overdose)
• If the anesthetic depth is increased and
passed stage 3 plane 4 , the animal enters
stage 4 . There is cessation of respiration ,
which may be followed by circulatory collapse
and depth . Immediate resuscitation is
necessary to save the patient life .

22. Types of general anesthetics
• General anesthesia mainly classified into two :
1 : Inhalational( it is dived into two GAS and
VOLATILE LIQUIDS )
2 : Intravenous( it is divided into two SLOWER
ACTING and INDUCING AGENT )

23. Inhalational anesthetics
• Divided into two classes:
1 :GAS : Nitrous oxide , zenon .
2 : Volatile liquids : Ether , halothane , enflurane
, isoflurane , desflurane , sevoflurane ,
methoxyflurane.

24. Intravenous anesthetics
• Divided into two classes:
1 : Slower acting ( divided into three groups)
A : Dissociative anesthesia : ketamine
B : Opioids : Fentanyl
C : Benzodizepenes : Dizepam , lorazepam ,
midazolam.
2 : Inducing agents : Thiopentone , methohexitone ,
propofol , etomidate , droperidol , Barbiturates
(thiopental sodium) .

25. Side effects of anesthesia
• In Cats
• Some of the most common side effects in cats include allergic
reactions , vomiting and to it pneumonia , organs failure , kidneys
damage , seizers(heart condition) .
• Common side effects of anesthesia can be seen during recovery ,
including a reduced ability to control his body temperature ,
increased vocalization due to disorientation , and a lack of
coordination .
• In Dogs
• Mild dog anesthetic side effects include injection site swelling or a
faint decrease in cardiac output . Catastrophic effects include
anaphylactic shock or death.
• Others like vomiting , aspiratory pneumonia , seizers , visual
impairment , clotting disorders (like von Willebrand’s disease in
dogs and system failures of the liver , kidneys or heart .

26. Continue:
• In Cattles :
• Salivation or inability to swallow the normal salivation volume .
• Hypoxia due to hypoventilation .
• General anesthesia sufficient for surgery , but was associated with
cardiopulmonary depression and prolong recovery .
• Weight of the cattle is more so if we put them on general anesthesia to
knock them out completely , their size puts so much pressure on the side
next to the ground that it inhibits the flow of blood to those tissues.
• Lungs size are huge so more anesthetics and huge respiration machine is
require to help them breath .
• When cattle are recumbant for more time so there will be chance of bloat
formation.

27. Continue
• In Horses:
• The extent of reaction can range from mild
skin wheals to collapse , inability to breath
and death (anaphylaxis) .
• We cannot sedate or recumbant the horse
more than 20 minutes it will cause serious
problem .

28. Selection of the Anesthetic Protocol
• The patient physical status is not only factor that
determines the anesthetic protocol to be used. Other
factors that affect the veterinarian decision include the
following.
• Availability of facilities and equipment.
• Familiarity with the agent.
• Nature of procedure or operation.
• Special patient circumstances.
• Cost of anesthetic protocol.
• Speed of the drug (induction , distribution, and
excretion)

29. Anesthetic protocols
• In Dogs
• For controlling ferocious dogs .
1 : Acepromazine 0.03-0.05mgkg , IM , BW wait for
20-25 minutes for excellent tranquillization
(doesnot provide analgesia)
2 : Inj. Dizepam - 1mgkg , BW , IV
3 : Inj. Xylazine – 1mgkg , BW , IM
4 : Inj. Buturm – 0.2mgkg, BW , IM + Inj.
Acepromazine -0.02 -0.03mgkg BW , IM

30. First combination in dogs
• Atropine – 0.04mgkg SC after 15 – 20 minutes
• Xylazine – 2mgkg BW + Ketamine – 10mgkg BW , mixed in a single
syringe IM and maintenace mostly by ketamine using IV route.
• Duration of anesthesia is 5-15 minutes.
• Second combination in dogs
• Atropine – 0.04 mgkg SC after 15 minutes
• Dizepam – 0.4 mgkg + Ketamine – 6-12mgkg in a single syringe IV and
maintenace mostly by Ketamine using IV route .
• Duration of anesthesia is 5-15 minutes .
• Third combination in dogs
• Atropine – 0.04mgkg SC after 15 minutes give
• Dizepam @ 0.5mgkg , BW , IV after 5 minutes give
• Inj Propofol @ 5mgkg , IV

31. In Cats
• First combination
• Atropine – 0.04mgkg SC and after 15 minutes give
• Acepromazine – 0.1mgkg SC and after 15 minutes give
• Ketamine 2-8mgkg IM or IV
• Duration of anesthesia 5-10 minutes IV , 15-20 min IM.
• Second combination
• Atropine -0.04mgkg SC and after 15 min give
• Xylazine – 1mgkg IM and after 5 minutes give
• Ketamine – 10mgkg IM
• Duration of anesthesia is 12-15 minutes , redosing if necessary can be
done with Ketamine “to effect”
• Third comination
• Propofol 2-8mgkg IV induction ( dose to effect) maintenance by )0.2-
0.4mgkgmin IV infusion

32. In Horses
• First combination
• Acepromazine @ 0.03-0.05mgkg , IV and than wait for 20 minutes and give
• Thiopental sodium @ 8-10mgkg , IV
• It will work for 20 minutes .
• Second combination
• Xylazine @ 0.5-1mgkg , IM wait for 15 minutes and than give
• Thiopental sodium @ 5mgkg , IV
• It will work for 20 minutes .
• Third combination
• Xylazine @ 0.5-1mgkg , IM and wait for 15 minutes and than give
• Ketamine @ 2mgkg IV
• Fourth combination
• Xylazine @ 0.3-0.8 mgkg , IM
• Ketamine @ 2mgkg IV
• Dizepam @ 0.1-0.5mgkg

33. In Cattle
• In cattle we used more local anesthesia
( regional anesthesia) due to certain problems
which are discussed previously . It,s not that
mean that we should not use general
anesthetics , we should used it if needed .
• We use in cattle the combination of local
anesthetics as
• Preanesthetic ( Xylazine @ 0.02mgkg)
• Local anesthetic ( lignocaine 2%)

34. The End
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