The document discusses various types of anesthetics used for fish. It describes how anesthetics induce temporary loss of sensation or awareness by depressing the nervous system. The most common methods of anesthesia for fish are immersion, where the fish breathes in the anesthetic dissolved in water, and injection directly into the body. The document outlines specific anesthetics commonly used like MS-222, benzocaine, lidocaine, metomidate and clove oil. It provides dosage guidelines and notes factors like water temperature that impact effectiveness. Stages of anesthesia and recovery are also summarized.

1. Presented by:-

2. ANAESTHETICS
 An anesthetic or anaesthetic is a drug used to induce
anesthesia — in other words, to result in a temporary
loss of sensation or awareness.
 Anesthesia is generally defined as a state caused by an
applied external agent resulting in a loss of sensation
through depression of the nervous system. Anesthetics
may be local or general, depending on their application.

3.  Anaesthetics are distinct from analgesics, which block only
sensation of painful stimuli.
 A wide variety of drugs are used in modern anesthetic
practice.
 Many are rarely used outside anesthesiology, but others
are used commonly in various fields of healthcare.
 Combinations of anesthetics are sometimes used for
their synergistic and additive therapeutic effects.

4. ANESTHETICS IN AQUACULTURE
 Fish are easily stressed by handling and transport and
stress can result in immuno-suppression, physical injury,
or even death.
 An ideal anesthetic should induce anesthesia rapidly
with minimum hyperactivity or stress
 It should be easy to administer and should maintain the
animal in the chosen state.

5.  Although the use of anesthetics is primarily for the
purpose of holding fish immobile while the animal is
being handled for sampling
 Anesthetics are also used to lower the level of
stress associated with such procedures.
 Overdose of anesthetics is also used routinely as
an effective and humane means of euthanizing fish.

6. STAGES OF ANESTHESIA
 Induction
 Maintenance
 Recovery

7. INDUCTION
 Most anesthetics can produce several levels or
stages of anesthesia. Stages include sedation,
anesthesia, surgical anesthesia and death.
 When an anesthetic is first administered (induction)
fish may become hyperactive for a few seconds.
 The stage achieved usually depends on the dose
and the length of exposure.

8. MAINTENANCE
 Once the desired degree of anesthesia is reached, it may
be desirable to maintain fish in that state for some time.
 A desired level of anesthesia can usually be maintained by
reducing the dosage.
 The condition of the animals must be visually monitored
during this maintenance period
 A change in breathing rate is the most obvious indicator
of over-exposure.

9. RECOVERY
 During the recovery stage the anesthetic is withdrawn
and fish return to a normal state.
 Initial recovery may take from a few seconds to several
minutes, depending on the anesthetic administered.
While ,Full recovery can take minutes to hours, depending
on the species and drug used.
 If an animal fails to recover, increasing the flow of
anesthetic-free water over the gills will often accelerate
and normalize the heart beat.

10.  Move the fish backwards and forwards in the
recovery bath or gently pass water over the gills
with a hose.
 This increases gill blood flow and eliminates the
drug more rapidly.

11. STAGES OF ANESTHESIA AND RECOVERY
 Stages of Anesthesia Description
 Stage I Loss of equilibrium
 Stage II Loss of gross body movements but with
continued opercular movements
 Stage III As in Stage II with cessation of opercular
movements
 Stages of Recovery
 Stage I Body immobilized but opercular
movements just starting
 Stage II Regular opercular movements and gross body
movements beginning
 Stage III Equilibrium regained and preanesthetic
appearance

12. FACTORS AFFECTING ANESTHESIA
 . These can be divided into
1) biological and
2) environmental factors.
 The rate at which anesthetic drugs become effective is
related to the gill area to body weight ratio, which can
vary considerably among fish species.
 Aquatic species also have different metabolic rates
that affect the rate at which chemicals are absorbed
and anesthesia is induced.

13.  There are also factors that can affect anesthesia within a
particular species.
 Larger individuals generally require a greater
concentration of anesthetic than smaller individuals
 . At lower water temperatures, higher doses or longer
exposure times are required.
 The pH of an anesthetic solution also can influence its
efficacy, possibly by affecting the ratio of charged to
uncharged molecules

14. PRE-ANESTHETIC PREPARATION
 When possible, baseline behavioral parameters
(i.e., ventilation, caudal fin stroke rate, and overall
activity level) should be recorded.
 Stop feeding for 12 to 24 hours to decreases
nitrogenous waste production.
 Containers with adequate water for transportation,
maintenance, recovery, and possible required water
changes should be readily available.

15. TYPES OF ANAESTHESIA METHOD
1. Immersion method.
2. Oral method.
3. Injection method

16. IMMERSION ANAESTHESIA
 The fish ventilates the anesthetic in solution, which
enters the bloodstream through the gills, and skin
and then passes rapidly to the central nervous
system (CNS).
 Skin thickness and scalation affect uptake, with
thinner skin and loosely scaled or scale less
surfaces favoring drug uptake compared to thicker
skin or densely packed scaled surfaces.

17. INJECTION ANAESTHESIA
 Anesthetics can be delivered by
1. intravenously (IV)
2. intracoelomically (ICo)
3. intramuscularly (IM).
The most common injection method is IM injection.

18. EXAMPLES OF ANESTHESIA OF FISH
TMS
 TMS (MS-222), [3-aminobenzoic acidethyl ester
methanesulfonate] is the most widely used fish
anesthetic, and it is extremely effective for rapid induction
of deep anesthesia
 It is a white crystalline powder .
Precautions:
 TMS is generally safe to handle, but contact with eyes
and mucous membranes should be avoided (Merck and
Company, 1989), as irritation can result.

19. DOSAGES:
 25 to 100 mg/L
 TMS is also known as MS-222, TM18Finquel,
Tricaine, tricaine methanesulfonate and Metacaine.

20. BENZOCAINE
 Benzocaine [p-aminobenzoic acid ethyl ester]
 It has two forms:
1)a crystalline salt with a water solubility of 0.4g/L
2)a freebase form which must be dissolved in ethyl alcohol
first at 0.2 g/mL
Dosages:
The smallest fish require the lowest dose, as well as by the
temperature of the water.
25 to100 mg/L

21.  Benzocaine is also known as
TM1Anesthesin,
TM14Anesthone,
TM2Americaine,
ethyl aminobenzoate,
Orthesin and Parathesin.

22. LIDOCAINE
 Lidocaine [2-(diethylamino)-N-(2,6-dimethylphenyl)
acetimide]
 It is a cardiac depressant or injected as a nerve
block
 Dosages:
Lidocaine has been used in combination with sodium
bicarbonate to anaesthetize carp (Cyprinus carpio),
tilapia (Oreochromis/Tilapia mossambica) and catfish
(Ictalurus punctatus).

23.  . The addition of sodium bicarbonate, at 1 g/L, has
been demonstrated to enhance the anesthetic
effects of lidocaine. Without the addition of
bicarbonate, there are huge variations in required
doses. example, tilapia required in excess of 800%
more lidocaine than carp when it was administered
in the absence of sodium bicarbonate
 Lidocaine is also known as TM3Xylocaine.

24. METOMIDATE AND ETOMIDATE
 Metomidate [1-(1-phenylethyl)-1H-imidazole-5-carboxylic
acid methyl ester] watersoluble powder which has the
properties of a hypnotic, or sleep-inducing, drug.
 Etomidate [1-(1-phenylethyl)-1H-imidazole-5-carboxylic
acid ethyl ester] is a colourless, odourless crystalline
analogue of metomidate and propoxate.
 Precautions:
 A side effect of anesthesia with metomidate is muscle
twitching which can make blood sampling difficult

25. DOSAGES:
 Metomidate is effective in both fresh and saltwater,
and has been reported to be more potent in adult
salmon adapted to sea water
 Both drugs are fast acting with induction times of
less than 3 minutes and lengthy recovery times (up
to 40 minutes)
 Metomidate does not cause hyperactivity in the fish,
but concentrations above 3 mg/L have been shown
to block the cortisol response

26. PROPOXATE
 Propoxate [propyl-DL-1-(phenylethyl) imidazole-5-
carboxylate hydrochloride] is a crystalline powder which
resembles metomidate and etomidate structurally.
 It is freely soluble in both fresh water and salt water. It is
stable in solution for long periods and is 100 times more
soluble than TMS.
 Precautions:
Caution should be exercised at higher doses as respiratory
arrest occurs after 15 minutes at 64 mg/L, and after 1 hour
at 16 mg/L

27. DOSAGES:
 Effective concentrations range from 0.5 mg/L to 10
mg/L
 Propoxate is 10 times more potent than TMS.

28. KETAMINE HYDROCHLORIDE
 Ketamine hydrochloride [2-(0-chlorophenyl)-2-(methyl-
amino) cyclohexanone hydrochloride] is a white
crystalline powder.
 It has been widely used as an anesthetic both in human
and veterinary medicine
 Dosages:
A dose of 30 mg/kg for salmonids which results in
anesthesia in under 3 minutes, with a recovery time of 1 to
2 hours

29. QUINALDINE SULFATE
 Quinaldine sulfate [2-methylquinoline sulfate] is a
light yellow crystalline powder which has a water
solubility of 1.041g/L.
 It is one of the most widely used anesthetics by
marine biologists to collect tidepool and coral reef
fishes.
 Dosages:
Quinaldine sulfate is effective at water pH levels
above 6.

30. PROPANIDID
 Propanidid (4-[2-(diethylamino)-2-oxoethoxy]-3-
methoxybenzeneacetic acid propyl ester) is a pale
yellow liquid which is insoluble in water, but soluble
in alcohol.
 Dosages:
1.5 - 3.0 mL/L

31. CLOVE OIL AND DERIVATIVES
 As an alternative fish anesthetic
 Clove oil is a pale yellow liquid derived from the
leaves, buds and stem of the clove tree (Eugenia
sp.).
 Its active ingredients are eugenol (4-allyl-2-
methoxyphenol) and iso-eugenol (4-propenyl-
2methoxyphenol), which can comprise 90-95% of
clove oil by weight.

32. DOSAGES:
 40-60 mg/L
 Clove oil has been used for many years as a food
additive and a topical analgesic in dentistry, and is
recognized as a GRAS (Generally Recognized As
Safe) substance by the US FDA for use in humans.

33. 2-PHENOXYETHANOL
 2-Phenoxyethanol (2-PE) [1-hydroxy-2-
phenoxyethane] is a colourless, oily, aromatic liquid
with a burning taste.
 Precautions:
2-Phenoxyethanol is a mild toxin and may cause
some irritation to the skin, therefore any contact with
the eyes should be avoided.
Dosages
200 B 300 μL/L

34. METHYLPENTYNOL
 Methylpentynol [3-methyl-1-pentyn-3-ol] is a liquid
with a noxious odour and a burning taste.
 Methylpentynol is not recommended for use with
fish.

35. CHLOROBUTANOL
 Chlorobutanol [1,1,1-trichloro-2-methyl-2-propanol]
is a crystalline powder with a camphor odour.
 Chlorobutanol is also known as Chloretone

36. HALOTHANE
 Halothane [2-bromo-2-chloro-1,1,1-trifluoro-ethane]
is a non-flammable, highly volatile liquid with a
sweetish smell.
 It is not recommended for use with fish.

37. NON-CHEMICAL ANESTHESIA
 Electroanesthesia
 Hypothermia
 Carbon dioxide

38. CARBON DIOXIDE
 Carbon dioxide (CO2) is a colourless, odourless,
non-flammable gas .
 Precautions:
CO2 is safe to use, but a level of 10% or more in the
air will cause anesthesia or even death to the
operator; therefore, ample ventilation is necessary.

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