1. ~: Submitted by :~
Pramod Soni
Batch - B
Roll No.- 3733
COLLEGE OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY
NANAJI DESHMUKH VETERINARY SCIENCE, UNIVERSITY
~: Submitted to ~:
Dr. R .K. Sharma
Dr. Vidhi Gautam
Dr. Arpita Shrivastava
Dr. Sachin Jain

2. INTRODUCTION
 A general anaesthetic is a drug that brings about
a reversible loss of consciousness.
 General anaesthesia is essential to surgical practice
because it renders patient analgesic, immobile
and unconscious while causing muscle relaxation
and suppression of undesirable body reflexes.
 General anaesthetics widely used in medicine-ethanol,
chloroform, diethyl ether, halothane, isoflurane .

3. CLASSIFICATION
 The three main theories of general
anaesthesia
 Lipid theory
 Protein theory
 Biochemical theory

4. LIPID THEORY
Suggests thatthe anestheticacts nonspecifically onthe
lipid portions of the neuronalmembranetocauseageneral
disturbancethatcausestheionchannelsto change
structuretherebychangingtheir function
Interactions here cause
a physical change in the
membrane
Various lipid theory are given below-

5. MAYER AND OVERTON THEORY
 Mayer and Overton separate studies identically postulated that
anaesthetic potency varies with the lipid solubility.
 More the lipid soluble a drug is the greater is its anaesthetic
potency.
 This theory does not suggest any particular mechanism but
reflects only capacity of anaesthetic agent to enter into CNS and
attain sufficient concentration in neuronal membrane.
 It is now known that all highly lipid soluble substance s are not
anaesthetics and some potent anaesthetic are not lipid soluble.

6.  This theory also does not explain the cut-off
phenomenon

7. PAULING AND MILLER THEORY/HYDRATE THEORY
 This theory was given in 1961
 According to this theory simple molecules like water may be linked
together by hydrogen bonding to form ice like structures which are
occupied by anaesthetic agent to form anaesthetic hydrate crystals .
 These hydrates could then impede ionic mobility, electrical charge,
and chemical and enzymatic activity of the brain to produce
depression and unconsciousness.
 This theory does not explain anaesthesia produce by barbiturate and
some other anaesthetics

8. MEMBRANE EXPANSION THEORY
 Thistheorypostulatesthatanaestheticmoleculespenetrateinto
hydrophobic regionofthecellmembraneandcausesitsexpansion.
Themechanismofmembraneexpansionhasnotbeenfully
explainedbutmaybeattributabletoformationofhydrates.

9. MEMBRANE FLUIDISATION THEORY/
LATERAL PHASE SEPARATION THEORY
 This theory postulates that anaesthetic agents by
dissolving in the membrane lipids cause loosening
or fluidisation of lipid bilayer region of the
membrane .

10. PROTEIN THEORY
This theory suggests that the anesthetic must
act specifically with hydrophobic pockets on
certain membrane proteins to produce the
effect
n Lock and Key
n Problem: Too many keys that would have to
all fit the same lock
PROTEIN THEORY
 This theory suggests that the anaesthetic must act
specifically with hydrophobic pockets on certain
membrane proteins to produce the effect
 Lock and Key
 Problem: Too many keys that would have to
all fit the same lock

11. BIOCHEMICAL THEORY
 A number of biochemical theories have also been
postulated and reviewed .
 These include- inhibition of glucose metabolism in
brain cells, interference in production of ATP.
 Interference in oxygen utilization and cellular
respiration.

12. REFERENCES
 Essentials of veterinary pharmacology
and therapeutics 2nd edition by
Harpal singh sandhu.
 Essentials of Medical pharmacology
by KDTripathi.
 Internet.

13. THANKs