General Anaesthetics in Veterinary Medicine
Introduction to General Anaesthetics
Dr.Kumari Anjana
Assistant Professor
Deptt. of Veterinary Pharmacology & Toxicology
Bihar Veterinary College, Bihar Animal Sciences University, Patna
Introduction to General Anaesthetics
•
General anaesthetics are drugs that produce
reversible loss of all sensations and unconsciousness.
•
The
cardinal signs
of general anaesthesia are:
Loss of all sensation, especially pain
Sleep (unconsciousness) and amnesia
Immobility and muscle relaxation.
Abolition of somatic and autonomic
reflexes
Introduction to GA
contd…
•
No single drug is capable of achieving these effects
rapidly and safely.
•
Rather in the modern practice of balanced
anaesthesia, these effects are achieved by using
combination of drugs, each drug for a specific purpose.
•
General anaesthesia is generally employed in small
animal surgery, but not usually recommended in large
animal.
Large animals
are considered
unfit for general
anaesthesia
:
In recumbent position of animal, the
voluminous
rumen or stomach contents may enter in
respiratory tract due to regurgitation and
The distended rumen (accumulation of gases)
presses on diaphragm causing respiratory
distress
and
The
vena cava reducing venous return
resulting in
reduced cardiac output
(cardio-
vascular insufficiency).
Introduction to GA
contd…
Regional anaesthesia:
Reversible loss of sensations
of a large portion/area of the body (pelvic or
abdominal region) without affecting the
consciousness.
Surgical Anaesthesia:
A state of anaesthesia under
which the animal is in normal deep sleep, without
responding to painful stimuli, and surgical
operations can be carried out without causing pain
to the animal.
Neuroleptanalgesics
Combinations of
tranquillizers
(neuroleptics) and
opioids
called neuroleptanalgesics.
A state of CNS depression and analgesia that may cause
dramatic behaviour modification
and
change in
aggressiveness
in animals.
The most common combination is that of
fentanyl and
droperidol
.
The cardiopulmonary functions should be closely monitored
when neuroleptanalgesics are used as these drugs may
produce respiratory or haemodynamic depression ranging
from slight to significant.
Basal Anaesthetics
A
gents which produce a
lighter level of anaesthesia
(basal
anaesthesia), not suitable for surgical procedures, helps in
restraining
the animal.
Animal is unconscious
yet responds to painful stimuli
.
Basal anaesthesia is often induced before patient goes into
the operation theatre.
Agents :
Chloral hydrate, xylazine, paraldehyde,
pentobarbitone and diazepam
In some cases, basal anaesthesia can even be produced by
use
of pre-anaesthetics.
Balanced Anaesthesia
The general anaesthesia involves two phases i.e.,
induction
and
maintenance.
These can be achieved by use of either a
single anaesthetic agent or
more than one agents.
Except for short minor surgical procedures, the
use of a single
agent has been superseded by combination of two or more agents
to take
advantage of their desirable effects
(e.g., speed of
induction, skeletal muscle relaxation, depth and duration of
anaesthesia), while
simultaneously minimising their undesirable
effects
(e.g., respiratory depression, hypotension and
hepatotoxicity).
This practice of using two or more anaesthetics together with or
without supplementary medications is called basal anaesthesia.
Preanaesthetic medication
It consists of administration of certain drugs (for
specific purpose so as to produce balanced
anaesthesia) before General anathesia.
The drugs generally used as preanaesthetics are
Sedatives, Tranquillizers, Analgesics,
Anticholinergics (muscarinic blockers) and Muscle
relaxants.
They are administered about 30 minutes prior to
induction of anaesthesia.
Preanaesthetic medication
contd…
Classification of Preanaesthetics:
Preanaesthetic skeletal muscle relaxants:
d-Tubocurarine, Gallamine.
Preanaesthetic sedatives-
Xylazine, Meperidine
(Pethidine), Diazepam, Morphine, Butorphanol.
Preanaesthetic sedative antiemetic –
Acepromazine,
Chlorpromazine.
Preanaesthetics that diminish salivation and bronchial
secretions especially during inhalational anaesthesia and
to prevent cardiac arrest.
Atropine, Glycopyrrolate.
Classification of general anaesthetics
Based on route of administration
1. Inhalation Anaesthetics
2. Parenteral Anaesthetics or Injectable
3. Dissociative Anaesthetics
General anaesthetics induce reversible loss of sensations and unconsciousness, crucial for effective animal surgery. The use of a combination of drugs is essential to achieve safe and rapid effects in balanced general anaesthesia. Large animals present challenges due to their anatomy, making them unfit for general anaesthesia. Regional anaesthesia and neuroleptanalgesics offer alternative approaches for specific surgical needs while maintaining the animal's comfort and safety.
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Presentation Transcript
Introduction to General Anaesthetics Dr.Kumari Anjana Assistant Professor Deptt. of Veterinary Pharmacology & Toxicology Bihar Veterinary College, Bihar Animal Sciences University, Patna
Introduction to General Anaesthetics General reversible loss of all sensations and unconsciousness. anaesthetics are drugs that produce The cardinal signs of general anaesthesia are: Loss of all sensation, especially pain Sleep (unconsciousness) and amnesia Immobility and muscle relaxation. Abolition of somatic and autonomic reflexes
Introduction to GA contd No single drug is capable of achieving these effects rapidly and safely. Rather anaesthesia, these effects are achieved by using combination of drugs, each drug for a specific purpose. in the modern practice of balanced General anaesthesia is generally employed in small animal surgery, but not usually recommended in large animal.
Introduction to GA contd Large animals are considered unfit for general anaesthesia: In recumbent position of animal, the voluminous rumen or stomach contents may enter in respiratory tract due to regurgitation and The distended rumen (accumulation of gases) presses on diaphragm causing respiratory distress and The vena cava reducing venous return resulting in reduced cardiac output (cardio- vascular insufficiency).
Regional anaesthesia: Reversible loss of sensations of a large portion/area of the body (pelvic or abdominal region) without consciousness. affecting the Surgical Anaesthesia: A state of anaesthesia under which the animal is in normal deep sleep, without responding to painful operations can be carried out without causing pain to the animal. stimuli, and surgical
Neuroleptanalgesics Combinations of tranquillizers (neuroleptics) and opioids called neuroleptanalgesics. A state of CNS depression and analgesia that may cause dramatic behaviour modification aggressiveness in animals. The most common combination is that of fentanyl and droperidol. The cardiopulmonary functions should be closely monitored when neuroleptanalgesics are used as these drugs may produce respiratory or haemodynamic depression ranging from slight to significant. and change in
Basal Anaesthetics Agents which produce a lighter level of anaesthesia (basal anaesthesia), not suitable for surgical procedures, helps in restraining the animal. Animal is unconscious yet responds to painful stimuli. Basal anaesthesia is often induced before patient goes into the operation theatre. Agents : Chloral hydrate, pentobarbitone and diazepam In some cases, basal anaesthesia can even be produced by use of pre-anaesthetics. xylazine, paraldehyde,
Balanced Anaesthesia The general anaesthesia involves two phases i.e., induction and maintenance. These can be achieved by use of either a single anaesthetic agent or more than one agents. Except for short minor surgical procedures, the use of a single agent has been superseded by combination of two or more agents to take advantage of their desirable effects (e.g., speed of induction, skeletal muscle relaxation, depth and duration of anaesthesia), while simultaneously minimising their undesirable effects (e.g., respiratory hepatotoxicity). This practice of using two or more anaesthetics together with or without supplementary medications is called basal anaesthesia. depression, hypotension and
Preanaesthetic medication It consists of administration of certain drugs (for specific purpose so as to produce balanced anaesthesia) before General anathesia. The drugs generally used as preanaesthetics are Sedatives, Tranquillizers, Anticholinergics (muscarinic blockers) and Muscle relaxants. Analgesics, They are administered about 30 minutes prior to induction of anaesthesia.
Preanaesthetic medication contd Classification of Preanaesthetics: Preanaesthetic skeletal muscle relaxants: d-Tubocurarine, Gallamine. Preanaesthetic sedatives- (Pethidine), Diazepam, Morphine, Butorphanol. Preanaesthetic sedative antiemetic Acepromazine, Chlorpromazine. Preanaesthetics that diminish salivation and bronchial secretions especially during inhalational anaesthesia and to prevent cardiac arrest. Atropine, Glycopyrrolate. Xylazine, Meperidine
Classification of general anaesthetics Based on route of administration 1. Inhalation Anaesthetics 2. Parenteral Anaesthetics or Injectable 3. Dissociative Anaesthetics
