General Principles of Anesthesia discusses the history, definition, and stages of anesthesia. It covers the evolution of anesthesia from ancient times using plants for pain relief to the 18th century discoveries of ether and chloroform. The document outlines the four stages of general anesthesia proposed by Guedel (analgesia, excitement, surgical anesthesia, and paralysis), the mechanism of inhalational anesthetics, intravenous anesthetic groups, and components of an anesthesia machine including the frame, regulator, flowmeter, vaporizer, and breathing circuits. The future of anesthesia is discussed including new drugs, monitoring techniques, airway management, and addressing staffing needs to meet increasing demand for anesthetic services.

2. General Principles of
anaesthesia
DR.NADIR MEHMOOD
Asst professor
Department ofSurgery, RMC

3. L Os
What we will cover
 History
 Definition of Anesthesia
 Why is it important?
 Mechanism & stages
 Planning & pre-op fasting
 Equipment used
 Analgesia
 What is anesthetics?

4. Historical information
People always wanted to overcome the
sufferings caused by pain.
The history of civilization left numerous
documented evidences of permanent search
for ways and methods of anesthesia.
The first written mention of the pain relieving
medicines was found in Egypt (described in
Ebers papyrus 4 - 5 thousand years ago).
Use of wine, mandrake root, opium, Indian
hemp, henbane and thorn-apple.
In the East, in the mountains of
Tibet, acupuncture and massage were widely
used with anesthetic aim.

5. History of Anesthesia
• Ether synthesized in 1540 by Cordus
• Ether used as anesthetic in 1842 by Dr.
Crawford W. Long
• Ether publicized as anesthetic in 1846 by Dr.
William Morton
• Chloroform used as anesthetic in 1853 by Dr.
John Snow

6. • In the Crimean-Turkish war (1853 – 1856)
compatriot performed hundreds of successful ether
anesthesia during surgeries on gunshot injuries.
• In 1937 Guedel determined the clinical stages of
ether narcosis, which are still considered to be
classic.
• Since that time anesthesiology has begun its
scientific development.
• For 150 years of anesthesiology history, scientists
proposed and implemented in clinical practice
dozens of anesthetic preparations, both inhalation
and non-inhalation, as various types and methods
of pain relief. This stimulated development of
operative surgery and allowed various range of
surgical interventions in all organs and systems of
the body.

7. History of Anesthesia
• Endotracheal tube invented in 1878
• Local anesthesia with cocaine in 1885
• Thiopental first used in 1934
• Curare first used in 1942 - opened the “Age of
Anesthesia”

8. Anesthesiology
It is a science that studies how to protect
the organism from operating injuries. It
improves the well-known and develops
new methods of preparing patients for
surgeries, providing anesthesia,
controlling the body functions during the
operation and in postoperative period.

9. The 16th of October, 1846 is considered
to be the birthday of anesthesiology.

10. History of Anesthesia, 16th October 1846

11. So why no anesthesia until 1846?
No real concept of “anesthesia” in late 1700’s / early 1800’s
how can you achieve a state which you assume impossible or
cannot envisage achieving
Numerous Institutes concerned with treatment of disease by
“Physicians” - surgery did not have same standing and therefore
influence
State of surgery - almost inevitably fatal - why encourage them?
General moral / religious beliefs and fear / concerns about
animal experimentation
World Anesthesia Day 16th Oct

12. ARTIFICIAL AIRWAYS

13. ASSISTED VENTILATION
• MOUTH TO MOUTH VENTILATION

14. ASSISTED VENTILATION
AMBU BAG

15. LARYNGOSCOPY & INTUBATION

16. LARYNGOSCOPY & INTUBATION

17. LARYNGOSCOPY & INTUBATION

18. LARYNGOSCOPY & INTUBATION

19. LARYNGOSCOPY & INTUBATION

20. LARYNGOSCOPY & INTUBATION

21. Basic Principles of Anesthesia
• Anesthesia defined as the targetedly induced
loss of perception of all modalities
(touch, heat, cold, pain) of sensation
• a) reversible
• b) permanent (tumour pain)
• “Triad of General Anesthesia”
– need for unconsciousness
– need for analgesia
– need for muscle relaxation
• Analgesia defined as the abolition of pain

22. Stages of GA (Guedel I-IV )
• obviously present in ether monoanaesthesia (history)
• nowadays shortcut stage I, suppressed stage II
I. stage of analgesia (induction)
• from the initial administration to the loss of
consciousness
• normally responsive pupils, later dilation
• tachycardia
• tachypnoea
• unchanged skin reflexes
• marked analgesia – minute operations
(e.g: painfull re-bandage)

23. Stages of GA (Guedel I-IV )
II. stage of excitement
• from the loss of consciousness to the beginning of the
automatic respiration
• extremely marked excitation and motor agitation
• hypersalivation, increased emetic reflex
• arrhytmia, circulatory instability
• irregular respiration
• No action is allowed during this stage. Rapidly acting drugs
are used to minimize time in this stage and reach stage 3 as fast as
possible.

24. Stages of GA (Guedel I-IV )
III. stage of surgical anaesthesia
• automatic respiration to respiration arrest
• absent eye-lid and corneal reflex
• absent reaction to pain
• rhythmical eye-balls movements, sometimes nystagmus
• In this stage operations including tracheal intubation are
being done.

25. Stages of GA (Guedel I-IV )
IV. stage of paralysis (overdose)
• after stage III if administration of medication continues
• respiratory depression, first thoracic breathing, later
abdominal breathing
• cessation of respiration & circulatory collapse
• lethal without cardiovascular and respiratory support
• Warning signs: maximally dilated pupils, fading
photoreaction, irregular heart action, urinary & faecal
incontinence

26. STAGES OF GENERAL ANESTHESIA
(Guedel)
• Stage I: Analgesia
• Stage II: Excitement/ Delirium
• Stage III: Surgical Anesthesia
– Plane I:reg. breathing  loss of eye
movement
– Plane II initiation of IC muscle paralysis
– Plane III:  completion ICM paralysis
– Plane IV:  diaphragmatic paralysis
• Stage IV: Medullary Paralysis

27. Evaluation of inhalational anaesthetics
efficiency
Minimum alveolar concentration (MAC)
• Concentration of anaesthetic in alveolar space, that
prevents the reaction to a standard surgical stimulus
(skin incision) in 50% of subjects
• the lower MAC, the more potent anaesthetic
• immobility in 95% subjects: increasing concentration of
anaesthetic 30% over MAC
• before inhalational induction 2-5 minutes 100% oxygen->
denitrogenation -> faster induction
• at the end of anaesthesia again 100% oxygen -> faster
excretion of anaesthetic and waking up

28. Groups of intravenous anaesthics in use
1. barbiturates – thiopental
2. imidazoles – etomidat
3. alkyled phenols – propofol
4. steroids– althesin
5. eugenols – propanidid
6. phenylcyclidines – ketamine
7. benzodiazepines- midazolam

30. Anesthesia Components
– Frame
– Regulator
– Flowmeter
– Oxygen Flush
Assembly
– Vaporizer
– Anesthetic Supply
System
– Scavenging System
• Anesthesia Machine

31. Anesthesia Components
• Anesthesia Machine
– Frame
– Regulator
• Placed on O2 tanks to decrease pressure from
tank
• 2 types of tanks
– “E” Tanks
» 650L @ 1800PSI
– “H” Tanks
» 7100L @ 2200PSI
• Output pressure
adjusted with knob

32. Anesthesia Components
• Anesthesia Machine
– Frame
– Regulator
– Flowmeter
• Controls the amount of
air released into the
anesthetic circuit
• Calculation:
(Tidal volume - mL) x
(Breathes per minute) /
(1000mL/Liter)=
Liters Resp. per Minute

33. Anesthesia Components
• Anesthesia Machine
– Flowmeter
– Oxygen Flush Assembly
– Vaporizer
• Changes liquid agent to
a vapor
• Delivers the vapor into the moving
steam of oxygen in controlled amounts
• Must be serviced to maintain accuracy
of delivery and safety
• Caution with refurbished models

34. Anesthesia Components
• Anesthesia Machine
– Oxygen Flush Assembly
– Vaporizer
– Anesthetic Supply System
• a.k.a Breathing circuits
• Rebreathing
– Exhaled air is cleaned and reused with the patient
• Non-rebreathing
– Exhaled air is taken by scavenging system

35. Anesthetic Supply Systems
Rebreathing Circuit
Non-Rebreathing Circuit

36. The future
Anesthesia in the 21st Century
Crystal ball
 new and better drugs
“anaesthesia” perhaps not priority it was
NDMR(non dep musc relx) version of Suxamethonium
analgesia and PONV
 more TCI (Total comfort installation)
 “closing the loop” techniques
 new airway management techniques
 new monitoring - anesthetic depth
World Anesthesia Day 16th Oct

37. Anaesthesia in the 21st Century
• Staffing and workload issues
– increased demand for “anaesthetic services”
– questioning of roles outside theatre
– questioning of roles within theatre
World Anesthesia Day 16th Oct

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