Anesthetics

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Anesthetics

  1. 1. Anesthetics Priestly discovered first inhalation anesthetic nitrous oxide• Loss of sensation• Insensibility to the vital organs• Loss of consciousness is reversible• Temporary insensibility to pain or feeling in the bodyCharacteristics of anesthetic agent• Should give enough relaxation time• Inert, potent, non-flammable, non-irritating• Should not have toxic effect• Stable to light and heat• Economical• Analgesic action and muscle relaxation• Should not induce vomiting• Should not reduce blood pressure• Should not have any adverse effect with the administration of other drugs.
  2. 2. .Classification of anesthetics 1. General anesthetics 2. Local anestheticsGeneral anesthetics are further classified into a. Volatile general anesthetics b. Non-volatile anesthetics
  3. 3. Some of Volatile general anestheticsEther• Anesthetic ether is 96-98% diethyl ether• Colourless volatile liquid with pungent smell• Soluble in organic solvents like alcohol, chloroform, etc.• Prepared by williamson’s synthesis• Stored in well-closed, light resistant bottles• Inflammable.• When exposed in air it forms peroxides or acetic aldehydes• Stabilizers like sodium pyrogallate are added• Stored in internally copper plated containers.
  4. 4. Advantages .• Induces surgical anesthetics without pre- anesthetics medication• Safe• Produces muscular relaxation• Does not modify blood pressure• Economical and stable• Administered without a complicated processDisadvantages• Induction is slow• Boils at low temperature• Inflammable• Vapours are irritating to mucous membrane• Nausea and vomiting appear• Slow recovery• Ether convulsions may occur in children
  5. 5. Derivatives of ether were found to be less irritating than . etherMethyl-n-propyl ether• Powerful than ethyl ether• Less adverse side effectsVinyl ether• Colourless liquid• Miscible with alcohol, ether and chloroform• Stored in well closed container• Stored in cool, dark placeAdvantages• More potent• Speedy recovery• Useful in Dental procedures• Used in minor operations for short durationDisadvantages• Damages liver• Inflammable
  6. 6. Chloroform .• Powerful volatile liquid• Prepared from bleaching powder and ethyl alcohol• Colourless volatile liquid• 1-2% of ethanol is added to prevent the formation of poisonous phosgene gas• Should be protected from lightAdvantages• Induction is prompt• Vapours are not flammable• Used in obstetrical anestheticsDisadvantages• Toxic• Liver and cardiac toxicity• Due to its toxicity chloroform is no longer used
  7. 7. .Halothane• Fluorinated volatile liquid• Structure similar to chloroform• Heavy colourless liquid• Non-flammable• Sweet fruity odour• Miscible with chloroform, ether, etc.• Stored in air tight containers at low temperature• Should be protected from light• Stable in presence of alkalis
  8. 8. Advantages .• Not flammable• Does not irritate the respiratory passage• Nice pleasant odour• Potent anesthetics• Post operative vomiting is low• Relaxes bronchial muscle• Safe• Used as anesthetic during plastic surgeryDisadvantages• Causes cardiovascular depression• Depresses respiration• Poor analgesic• Expensive• Has to be given through a special apparatus• Hepatic damage• Used for intro-abdominal operation
  9. 9. Trichloroethylene .• Colourless• Characteristic odour• Thymol is added as preservative• Immiscible in water• Miscible with alcohol, chloroform, ether, etc• Stored in air tight and light resistant containers• Kept in cool placesAdvantages• Potent• Rapid onset of action• Recommended for short procedures such as dental extractions, etc.• Used for migraine pain, angina pectoris and child birthDisadvantages• Poor muscular relaxation• May be hepatotoxic and tachypnoea• Breaks down in the presence of soda lime to give highly toxic products
  10. 10. . Ethyl chloride• Non- irritating• Highly volatile• Inflammable• At ordinary temperature and pressure it is a gas• Pleasant characteristic odour• Miscible with organic solvents like alcohol and ether• Slightly miscible in water• Stored in air tight containers• When sprayed on skin it evaporates rapidly and cools the skin
  11. 11. .Advantages• Used as local anesthetic for minor operations such as incision, etc• As general anesthetic it induces anesthetic within 1 or 2 minutes• Quick inductionDisadvantages• May damage liver• Induce cardiac arrhythmias or cardiac arrest• Poor muscle relaxation• Low safety• Difficult to maintain steady depth of anesthetic
  12. 12. . Nitrous oxide• Colourless inorganic, non-irritating• Sweet taste• Non-flammable• Available in steel cylinders• Known as laughing gasAdvantages• Safest anesthetic• Non-flammable• Non-irritating• Rapid induction nad rapid recovery• Pronounced analgesic action• Does not induce post-operative nausea and vomiting• Used in painful procedures like cleaning and changing burn woundsDisadvantages• Not potent anesthetic• Pre-anesthetic medication has to be given• Produce violent excitation• Hypoxia• Increases cardiac irregularities
  13. 13. . Cyclopropane• Colorless sweet smelling gas• Available in metal cylinders in compressed form• Kept in cool placeAdvantages• Potent anesthetic• Has fast induction• Rapid and smooth recovery• Maintains blood pressure and cardiac contracitility• Used in hemorrhagic agent• Does not produce irritation of respiratory passage• Good muscle relaxant• Produces quite breathing• Supplies enough oxygen• Does not produce visceral damage
  14. 14. .Disadvantages• Induction is done carefully• Produce cardiac irregularities• Depresses respiratory center• Increases capillary oozing• Anesthetic mixture of cyclopropane and oxygen is explosive
  15. 15. Non-volatile anestheticsThiopental sodium• Yellowish white hygroscopic powder• Characteristic odour and bitter taste• Soluble in water• Solution is freshly prepared before using it in injection form• Stored in sealed containers• It is a derivative of barbituric acid and malonic ester• Patient passes through the stages of hypnosis and deep sleep to anesthesia• First consciousness is lost and then reflex activity and finally medullary centres are lost.• Used in minor operations such as fracture, dental surgerics, etc• Anti-convulsant
  16. 16. .Advantages• Non-explosive• Easy to administer• Induction is rapid and without any unpleasant feeling• Tendency of nausea and vomiting is very less• Does not effect respiration• No post-anesthetic complicationsDisadvantages• Needs constant supervision to avoid overdostage• Depresses vasomotor centre and myocardium• Poor analgesic• Does not produce muscular relaxation
  17. 17. Local anestheticsCharacteristics of local anesthetics• Non-irritant• Should not be painful• Low toxicity• Stable• Should not damage nerve cells• Sterilization of drugs should be easy• Should not damage nerve cells
  18. 18. The EstersCocaine• It is alkaloid obtained from leaces of Erthroxylon Coca• It is methyl benzoyl ester of Ecgonine which is a tropane derivative• Basic in nature• Levorotatory• White Crystalline powder• Sparingly soluble in water• Hygroscopic in natureAdvantages• Useful in surgery of nose, throat and eye• Local anaesthtic action• Stimulates central nervous systemDisadvantages• Drug is addiction• Dilates pupil• Raises blood pressure• Produces euphoria and fatigue• Poisonous in nature
  19. 19. .Benzocaine• Ester derivative• White crystalline powder• Stored in air tight containers• Light resistant containers• Soluble in water• Low toxicity• Available under the name anesthetic• Useful as dusting• Used in throat lozenges• Useful in relieving pain of gastric ulcer• Used in ointment form and is a surface anesthetic
  20. 20. The amidesLignocaine• Crystalline solid• Sparingly soluble in water• Used as hydrochloric salt• Very stable• Stored in room temperature• Resistance to hydrolysis• Used topically as surface anesthetic and ointment• Available in injection form as spinal nerve block injections• Quick onset of action• Good analgesic agent• Used for dental analgesia• Used in cardiac arrhythmias• Used for patients who are allergic to procaine• Toxicity is similar to that of other local anesthetics• May cause drowsiness

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