General anaesthetics, Notes for D.pharmacy

gerneral anaestheic chapter notes for D.pharmacy students

1. 2. Drugs Acting on CNS A) General Anaesthetics Prepared by – Mr. Digambar Jadhav ( M.Pharm ) HOD Padmini College of Pharmacy, Dighanchi.

2. Anaesthetics Definition – The drugs which are used to produce anaesthesia are known as anaesthetics. Anaesthetics General Anaesthetics Local Anaesthetics

3. General Anaesthetics Def :- “ These are pharmacological agents which when administered externally produces loss of sensation of pain with reversible loss of consciousness.” Stages of General anaesthesia : Stage of Analgesia and amnesia Stage of Delirium or excitement Stage of Surgical anaesthesia Stage of medullary paralysis

4. 1. Stage of analgesia This stage is in between induction of anaesthetics to loss of consciousness. It is characterized by loss of consciousness with feeling floating, numbness and analgesia. All reflexes are present This stage is suitable for dental surgery.

5. 2. Stage of delirium or excitements This stage is in between loss of consciousness and stage of surgical anaesthesia This stage start with loss of consciousness It is characterized by psychomotor excitement and hyperactivity of respiratory and cardiovascular reflexes This stage is not suitable for any surgical procedure.

6. 3. Stage of surgical anaesthesia This stage is starts when patients excitement is stopped and breathing is regularized It is characterized by fixed eye ball and shallow abdominal breathing All reflexes are completely abolished This stage is most suitable for major operation

7. 4. Stage of medullary paralysis It is a stage of overdose beyond the stage of surgical anaesthesia in which medullary centres are completely paralysed It is characterized by stoppage of breathing, fall of blood pressure to zero level and cardiovascular collapse. It leads to death Vigorous and prompt measure only can save the patient from this stage.

8. Classification Classification of General anesthetic is based on route of administration. General anesthetic drugs can be administered by Inhalation Intravenous

9. Classification ( A ) Volatile or Inhalatory anesthetics 1. Liquid : Ether Chloroform Halothane 2. Gases : Cyclopropane Nitrous oxide ( B ) Non-Volatile or Intravenous anesthetic 1. Barbiturate Thiopentone Kemithal 2. Non-barbiturate Propanedid Ketamine

10. Properties of Ideal General Anesthetic Easy for administer Should produce rapid and smooth induction and recovery Should be non-inflammable & non-irritating Should possess good analgesic effect Should possess adequate muscle relaxation Should possess sufficient margin of safety between stage of surgical anesthesia and stage of medullary paralysis Should be potent anasthetic with adequate duration of action Signs and stages of anesthesia should be clear

11. A ) Volatile or Inhalatory anesthetics 1. Ether Physical Properties : It is colourless, volatile liquid with pungent odour It boils at 35 C and vapours are irritant When ether is exposed to air, moisture or light, it get converted to ether peroxides and acetic aldehyde, which is irritant in nature Ether is highly explosive. It is stored in amber coloured bottles covered with black paper.

12. 1.Ether Advantages It is the safest anaesthetic agent with wide margin of safety even in unexperienced hands 90 mg/ 100 ml blood- induces anaesthesia 190 mg/ 100 ml blood- causes respiratory arrest It is not only a safe anaesthetic but a good analgesic also Ether does not modify blood pressure It does not have any effect on liver, kidney & heart It is an economical agent

13. 1. Ether Disadvantages I nduction is very slow and stormy Ether vapours are irritant and may increase salivary, bronchial secreation. Accumulation of secreation may induce cough & larynegal spasm Recovery is slow and is associate with high incidences of nausea & vomiting In children it may produce convulsions.

14. 1. Ether Preparation : Anaesthetic ether, I.P. Spirit of ether, I.P Dose : 1-4 ml Therapeutic uses : As General anaesthetic As rubefacients Used as solvent As cleansing agent

15. 2. Halothane Physical properties : It is heavy, colourless liquid. It is an inflammable, non-toxic fluorinated hydrocarbon. It has sweet, fruity odour and boils at 50 C. It affects most metals including stainless steel, brass and copper. It also affects rubber.

16. 2. Halothane Advantages : Induction is very smooth as it has sweet, fruity odour. Recovery is also fast, smooth with low incidences of nausea and vomiting. It does not cause irritation of respiratory passage. It does not produce bronchospasm, hence can be used in patients with bronchial asthma.

17. 2. Halothane Disadvantage : Muscular relaxation is inadequate. It causes respiratory, cardiovascular depression. Mental recovery is delayed Shivering during recovery is very common It is a poor analgesic It is expensive, need special apparatus for administration.

18. 3. Chloroform It is no more used for therapy because of its : Hepatotoxicity Nephrotoxicity cardiotoxicity

19. 4. Cyclopropane Physical properties : It is a colourless gas with sweet odour and taste. It is available as liquid under pressure and administered in closed circuit. Advantages : It is a potent anaesthetic agents. Induction is pleasant and quicker. Recovery is rapid and smooth Does not irritate respiratory passage Incidences of nausea and vomiting are less It produces adequate muscular relaxation It does not affect blood pressure and cardiac contractility.

20. 4. Cyclopropane Disadvantages : The signs of anaesthesia are not clear. Rapid induction may produce laryngospasm, breath holding, coughing Stages of anaesthesia are not clear , as induction is very smooth.

21. 5. Nitrous Oxide Physical properties : It is colourless gas with sweet odour and taste It is non-inflammable Advantages : It is non-inflammable and non-irritant. It produces rapid induction and recovery. It has good analgesic effects & hence can be used in dental practice. It is safest anaesthetic agent. Incidences of nausea & vomiting are rare

22. 5. Nitrous Oxide Disadvantages : Pre- anesthetic medication is required as it is not a potent anaesthetic. Excitement may be violent. Special apparatus is required.

23. b) non –volatile / intravenous anaesthetics Advantages : Easy for administration Induction is rapid and smooth Post-anaesthetic complication are rare Recovery is very fast Respiratory and myocardial functions remains unaffected No irritation of respiratory passage.

24. b) non –volatile / intravenous anaesthetics Disadvantages : Usual stages of anaesthesia are not clear. Coughing, apnea is common during induction Muscular relaxation is very poor. Injection around nerve may produces pain. Preparations Thiopenton sodium : 2.5% solution Methohexitone : 1% solution Propanidid : 4 mg/kg Ketamine : 1.2 mg/kg

25. Preanaesthetic Medication Def :- “ These are the drugs used prior to the administration of an anesthetic agent, with the important object of making anesthesia safe and more agreeable to the patient .”

26. Aim & Objective For sedation – to reduce anxiety To obtain an additive or synergestic effect To minimise pre and post operative complication To facilitate smooth and rapid induction To overcome secretary effects of general anaesthetics.

27. Various agents preferred as preanaesthetic anaesthetics are as follows Sr. No Type Drug 1 Opioid analgesic Morphine 2 Anxiolytic Diazepam 3 Anti-emetic Promethazine 4 Antisecretory Atropine 5 Skeletal muscle relaxant D- tubocurarine