1. Introduction to General Anaesthesia
Dr Anthony Ho

2. Points to discuss
What is general anaesthesia?
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
Immobile patient with relaxed muscles
Good outcome

5. Patients’ Requirements
Asleep
Alive
No pain or nausea

6. The Basic Components of General Anaesthesia

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

8. The triad of balanced general anaesthesia1
The triad of balanced general anaesthesia
1. Unconsciousness
“sleep”
“hypnosis”
“lack of awareness”

9. The triad of balanced general anaesthesia2
2. Analgesia
Reduction of physiological “stress” responses (sympathetic, CVS, hormonal)
Prevention of hypersensitization
Continuation postoperatively

10. The triad of balanced general anaesthesia3
3. Muscle relaxation
Skeletal muscle paralysis
(Voluntary and reflex)
Permits surgical access
Allows tracheal intubation and mechanical ventilation
Varies for different operations

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

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

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

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

15. Curare

16. (Opium) Papaver somniferum

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

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
examples:
Thiopentone, propofol
Isoflurane, sevoflurane, halothane

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

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

22. The Process of General Anaesthesia

23. The Process of General Anaesthesia
1. Preparation
2. Induction
3. Maintenance
4. Emergence
5. Recovery

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

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

26. Maintenance Ventilation plus as required: Oxygen 30% Nitrous oxide 70%
Isoflurane %
plus as required:
Muscle relaxant
Opioid
± Regional block

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

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

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