ANAESTHESIA OF LABORATORY ANIMALS

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ANESTHESIA OF LABORATORY ANIMALS:

ANESTHESIA OF LABORATORY ANIMALS SWETHA BEERAM Y11MPH474 M.PHARMACY DEPARTMENT OF PHARMACOLOGY 1 CHALAPATHI INSTITUTE OF PHARMACEUTICAL SCIENCES

WHAT DOES THE WORD MEAN?:

WHAT DOES THE WORD MEAN? Anesthesia = without sensation an = without, aestos = sensation A controllable and reversible condition in which sensory perception and motor responses are both markedly depressed. 2

THE IDEAL ANESTHESIA:

THE IDEAL ANESTHESIA Reversible and controlled loss of consciousness “No” mortality Undisturbed physiology/vital functions Minimal homeostatic changes Optimal conditions for surgery Relief of pain, stress and discomfort Easily administered Economic 3

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Unconscious Muscle relaxation Pain relieve THE ANESTHETIC TRIANGLE 4

Why is anesthesia necessary?:

Why is anesthesia necessary? Ethical reasons – “Should an experiment be assumed to be painful, anesthesia must be used” Practical / technical reasons – “chemical restraint” ‐ avoid stress and trauma 5

PROS AND CONS OF ANESTHESIA :

PROS AND CONS OF ANESTHESIA Pros no pain no muscle reflexes no muscle tension Clinical anesthesia Cons changes in the body physiological status different responses may be different Research anesthesia 6

PRE ANESTHETIC CARE (BEFORE ANESTHESIA) “Peaceful induction - be calm and quiet”:

PRE ANESTHETIC CARE ( BEFORE ANESTHESIA ) “Peaceful induction - be calm and quiet” 7

“PLANNING IS HALF THE JOB” :

“PLANNING IS HALF THE JOB” WHY ? Crucial for satisfying anesthesia Minimize anesthesia complications Smooth running of research protocol HOW ? Includes preparation of both animal, drugs, facilities, personnel. Peaceful induction ‐ avoid sharp sounds and sharp light 8

INSPECTION BEFORE ANAESTHESIA:

INSPECTION BEFORE ANAESTHESIA Check animals before starting Do not anesthetise sick animals Pay attention to symptoms of infections Running eyes, diarrhea, reduced appetite, abnormal behavior Weigh the animal before anesthesia to adjust anesthetic dose 9

ACCLIMATIZATION :

ACCLIMATIZATION A period of acclimatization is needed to allow animals to – Recover metabolic and hormonal changes caused by transport stress – Recover weight, hydration and food consumption – Familiarize to new environment, staff and routine. 10

FASTING:

FASTING Pre‐operative fasting minimizes risk of vomiting – Dogs, cats, pigs ‐ 12 hours – Ruminant ‐ 12‐24 hours (reduce accumulation of gas in rumen) – Rodents: Usually unnecessary 11

PRE-ANAESTHETIC MEDICATION:

PRE-ANAESTHETIC MEDICATION Reduce fear, provide sedation and stress free induction to anesthesia Reduce amount of anesthetic drug needed Smoother induction and recovery from anesthesia Reduce volume of salivary and bronchial secretions Block “ vaso‐vagal effect” Reduce preoperative pain and minimize post operative pain 12

PowerPoint Presentation:

ANTI-CHOLINERGIC DRUGS: – Reduce bronchial and salivary secretions – No vagal reflexes, less gut motility – Correct slow heart rate. EX: Atropine, glycopyrolate SEDATIVES: – Sedation, potentiate anesthetics EX: Phenothiazines , Benzodiazepines ALPHA 2 ADRENERGIC AGONISTS – Sedation, moderate analgesic effect – Respiratory depression EX: Xylazine and Medetomidine‐Rompun 13

PRE-ANAESTHETIC HYDRATION:

PRE-ANAESTHETIC HYDRATION Give animal balanced electrolyte fluid to drink couple of days before Yields better water balance Continue a few days after anaesthesia 14

PERI‐ANESTHETIC CARE (DURING ANESTHESIA):

PERI‐ANESTHETIC CARE (DURING ANESTHESIA) Monitoring of anesthesia • Close observation of the animal • Rate and pattern of respiration • Rate and quality of the pulse • Temperature 15

“APPROPRIATE CORRECTIVE ACTION”:

“APPROPRIATE CORRECTIVE ACTION” Give fluids Adjust anesthetic depth Prevent heat loss (hypothermia) Provide pain killers (analgesia) Oxygenation (increase O 2 concentration in fresh gas) 16

COURSE OF ANESTHESIA:

COURSE OF ANESTHESIA I. Stage of analgesia II. Stage of excitation III. Stage of tolerance IV. Stage of asphyxia V. No reflexes, no respiration: danger of death 17

ASSESSMENT OF ANAESTHETIC DEPTH:

ASSESSMENT OF ANAESTHETIC DEPTH Respiratory rate, Cornea Tail pinch and Pedal reflex Ear pinch 18

TYPES OF ANESTHESIA:

TYPES OF ANESTHESIA LOCAL ANESTHESIA GENERAL ANESTHESIA Regional and reversible elimination of pain Complete unconsciousness (Whole body) Procaine , Butanilicaine , Lidocaine , Mepivacaine Barbiturates Chloralhydrate Isoflurane Isoflurane Gentle and calm animals (cattle, sheep). Rats, Mice, Guinea Pigs 19

ROUTES OF GENERAL ANESTHESIA:

ROUTES OF GENERAL ANESTHESIA INJECTION INHALATION Barbiturates Halothane Chloralhydrate Isoflurane Urethane Methoxyflurane Xylazine and Ketamine Carbon dioxide 20

INJECTION ANESTHESIA:

INJECTION ANESTHESIA Anesthetic compound is dissolved in a liquid. Route of administration- INTRAPERITONIAL SUBCUTANEOUS INTRAVENOUS 21

BARBITURATES:

BARBITURATES For laboratory animals short and very short acting barbiturates are used predominantly (sodium pentobarbitone , thiopental, hexobarbital ) Barbiturates are not analgesic and should not be given without opioids . Pentobarbital can induce severe cardiovascular and respiratory depression. 22

URETHANE:

URETHANE Urethane produces long lasting anesthesia (10 hrs) with rapid onset following IP administration. It has minimal effects on the cardiovascular and respiratory systems. Good analgesia as well as excellent muscle relaxation. DISADVANTAGES- At high doses, hypotension, hypothermia, bradycardia and liver toxicity are seen. It is a proven carcinogen and mutagen in rodents. Not recommended for survival procedures. 23

KETAMINE:

KETAMINE Ketamine is a neuroleptic compound with a very fast onset of action following intramuscular administration. It can be used for nearly all species. A side effect of this compound is an increased tonus of skeletal muscles but this can be prevented by the simultaneous administration of xylazine or diazepam. 24

INHALATION (THROUGH THE LUNGS):

INHALATION ( THROUGH THE LUNGS) More common for the bigger laboratory animals such as dogs, cats, sheep, goats and monkeys. The advantages are the possibilities of controlling exactly the depth of anesthesia and of fast management of complications. 25

HALOTHANE :

HALOTHANE Common and cheapest inhalation compound Does not evaporate concentrations with mortality at room temperature Good clinical anaesthesia with guidance DISADVANTAGES Reduces cardiac output. Causes hypotension. Respiratory depressant. Liver necrosis 26

ISOFLURANE:

ISOFLURANE More expensive than halothane Requires own vaporizer Very rapid induction and recovery from anaesthesia Non-irritant in the airways, but has a pungent smell Limited toxic influence on liver and kidney No analgesic effect!!! 27

CO2:

CO 2 Useful for 1-2 min procedures For rats and mice A ratio of 70% CO2 to 30% O2 for anesthesia Nasal bleeding, excessive salivation, seizures, and even death 28

No ether, neither chloroform:

No ether, neither chloroform Evaporate to mortal concentrations at room temperature Ether explodes, and carcasses in cooler of freezer smell a long time Chloroform is liver toxic and suspected carcinogen 29

DIFFERENT TECHNIQUES:

DIFFERENT TECHNIQUES Technique of insufflations - performed via a mask. Open system - Inspired and expired gases are separated by a valve. “Stephen slater ” 30

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Closed systems In closed systems all of the expired air passes to a CO 2 absorber. The CO 2 is removed chemically and the air is inspired again with newly evaporated anesthetic compounds mixed with oxygen. Half-closed - In this part of the expired air reaches the atmosphere. 31

METHODS OF INHALATION:

METHODS OF INHALATION Open Drop-bell jar Vaporizer 32

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Endo-tracheal intubation 33

POSTOPERATIVE CARE:

POSTOPERATIVE CARE Temperature Infrared light bulb Insulation Fluid I.P or S.C as boluses Air humidification Additional oxygen Oxygen flow to chamber RECOVERY CHAMBER 34

Eyes stay open and….dry:

Eyes stay open and….dry 35

ADVERSE EFFECTS OF ANESTHESIA:

ADVERSE EFFECTS OF ANESTHESIA Common adverse affects of anesthesia Depression of Respiration Heart rate Blood pressure Body temperature (increased heat loss) Care has to be taken to avoid adverse effect or death caused by anesthesia !!! Anesthesiology ABCT • Airway control • Breathing Control • Circulatory Control • Temperature 36

CONCLUSION:

CONCLUSION A comprehensive individualized anesthetic plan will minimize peri -operative morbidity coniditions . The most successful anesthetic protocols, however comes with practice. 37

REFERENCES:

REFERENCES H. Gerhard Vogel (Ed.) Drug Discovery and Evaluation, Pharmacological Assays, 2 nd Edition,2002. Guidelines for care and use of animals in Scientific Research, Indian National Science Academy, New Delhi. CPCSEA guidelines for animal care and handling. P.Flecknell . Laboratory Animal Anaesthesia. Academic Press, 1996 D.H. Kohn, S.K. Wixson , W.J. White, G.J. Benson. Anesthesia and Analgesia in Laboratory Animals. Academic Press 1997. Google images 38

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