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Introduction to General Anaesthesia Dr Anthony Ho.

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Presentation on theme: "Introduction to General Anaesthesia Dr Anthony Ho."— Presentation transcript:

1 Introduction to General Anaesthesia Dr Anthony Ho

2 Points to discuss n What is general anaesthesia? n How do we do it?

3 What is general anaesthesia? What are the objectives? 1. Provide conditions suitable for surgery a) for surgeon b) for patient 2. Maintain physiological homeostasis 3. Restore normal function afterwards

4 Surgeons Requirements n Immobile patient with relaxed muscles n Good outcome

5 Patients Requirements n Asleep n Alive n No pain or nausea

6 The Basic Components of General Anaesthesia

7 The triad of balanced general anaesthesia Unconsciousness (3) Muscle relaxation Analgesia (2) (1)

8 1. Unconsciousness n sleep n hypnosis n lack of awareness The triad of balanced general anaesthesia 1

9 2. Analgesia n Reduction of physiological stress responses (sympathetic, CVS, hormonal) n Prevention of hypersensitization n Continuation postoperatively The triad of balanced general anaesthesia 2

10 3. Muscle relaxation n Skeletal muscle paralysis (Voluntary and reflex) n Permits surgical access n Allows tracheal intubation and mechanical ventilation n Varies for different operations The triad of balanced general anaesthesia 3

11 How to do it... n Depressant and inhibitory drugs n Controlled n Reversible

12 H H H H H C C O C C C H H H H

13 First use of ether anaesthesia, Boston, USA, 1846

14 Diethyl Ether Unconsciousness (3) Muscle relaxation Analgesia (2) (1)

15 Curare

16 (Opium) Papaver somniferum

17 Balanced anaesthesia: Use of selective drugs Unconsciousness (3) Muscle relaxation Analgesia (2) (1)

18 Balanced anaesthesia uses selective drugs 1. Unconsciousness –Intravenous and inhalational anaesthetics 2. Analgesia –Opioids 3. Muscle Relaxation –Neuromuscular blockers

19 Balanced anaesthesia uses selective drugs 1. Unconsciousness –Intravenous anaesthetics –Inhalational volatile anaesthetics n examples: –Thiopentone, propofol –Isoflurane, sevoflurane, halothane

20 Balanced anaesthesia uses selective drugs 2. Analgesics: Opioids n Morphine n Fentanyl n Pethidine, alfentanil, remifentanil

21 Balanced anaesthesia uses selective drugs 3. Muscle relaxants n a) Depolarizing: –Suxamethonium n b) Non-depolarizing: –Vecuronium, rocuronium –Atracurium, cisatracurium, mivacurium

22 The Process of General Anaesthesia

23 1. Preparation 2. Induction 3. Maintenance 4. Emergence 5. Recovery

24 Preparation (Preoperative n Ward * (Preoperative assessment, premed) n Transfer to OT n Equipment check * n Monitoring * n IV access, * IV infusion, * other lines n Preoxygenation

25 Induction n Usually IV n Muscle relaxant n Manual ventilation * n Tracheal intubation ( * )

26 Maintenance n Ventilation –Oxygen 30% –Nitrous oxide 70% –Isoflurane 0.5 - 1% n plus as required: –Muscle relaxant –Opioid Regional block

27 Emergence n Cessation of inhaled agents n Reversal of muscle relaxants n Extubation

28 Recovery n Return of consciousness n Analgesia * n Management of complications * –Nausea and vomiting –Cardiorespiratory –Hypothermia

29 Summary n General anaesthesia more than just sleep n Maintenance of homeostasis is a priority n Target drugs are used for specific endpoints for balanced effect n All anaesthetic effects are reversible n Anaesthetic care extends beyond the operating theatre


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