This document provides an introduction to anesthesia. It defines anesthesia as "no sensation" and discusses the history of anesthesia from the 18th century discoveries of nitrous oxide and ether to the development of modern inhalational and intravenous anesthetic agents in the 20th century. It also summarizes the key events in the history of anesthesia including the first public demonstration of ether anesthesia in 1846. The document outlines the components and techniques of general anesthesia and discusses different anesthetic agents including inhalational gases, intravenous drugs, and local anesthetics.

1. In the name of Allah

2. Introduction to Anesthesia
Dr. M.Masjedi
Ass. Prof. of anesthesia,
Fellowship of critical care medicine
SUMS - 2015

3. Definition of Anesthesia
Anesthesia literally means “no sensationno sensation”
Derived from the Greek verb for “to perceive”
Oliver Wendell Holmes suggested the name "Anesthesia"

4. History of AnesthesiaHistory of Anesthesia
1818thth
Century SurgeryCentury Surgery
Original in the Royal College of Surgeons of England, London.

5. Historical ReviewHistorical Review
1771-Joseph Priestly1771-Joseph Priestly
- discovery of 02- discovery of 02
1772-Joseph Priestly - discovery1772-Joseph Priestly - discovery
of N20of N20
Late 1700's-Pneumatic MedicineLate 1700's-Pneumatic Medicine

6. Historical ReviewHistorical Review
1798-1798- Sir Humphrey DaviesSir Humphrey Davies first mention offirst mention of
inhalational properties ofinhalational properties of N20N20 ( relief of pain( relief of pain
caused by an erupting wisdom tooth) butcaused by an erupting wisdom tooth) but
cliniciansclinicians overlookedoverlooked his suggestionhis suggestion
1846-1846- Horace WellsHorace Wells :observed significant leg:observed significant leg
injury without pain , next day received N2Oinjury without pain , next day received N2O
forfor extraction of one his teethextraction of one his teeth
Early 1800's -Early 1800's - recreational use ether frolicsrecreational use ether frolics

7. History of AnesthesiaHistory of Anesthesia
 1540 : A1540 : A flammable ,volatile liquid synthesized byflammable ,volatile liquid synthesized by
Cordus (Cordus (sweet vitriolsweet vitriol))
 1740 : Frobenius named it1740 : Frobenius named it EtherEther (from the greek word(from the greek word
for ignate or blaze)for ignate or blaze)
 1842 Used1842 Used as anestheticas anesthetic , publicized, publicized as anesthetic inas anesthetic in
1846 by Dr. William Morton1846 by Dr. William Morton
 ChloroformChloroform used as anesthetic in 1853 by Dr. John Snowused as anesthetic in 1853 by Dr. John Snow

8. One of the most significant events in the history of medicine
O ct. 1 6 , 1 8 46 - Ether Day : First demonstration of the use
of ether in anesthesia at Mass. Gen. Hosp.( Ether dome )
-Dr. William T.G. Morton ( First anesthesia specialist)

9. Historical ReviewHistorical Review
1850’s -1850’s - Chloroform/EtherChloroform/Ether - multiple deaths- multiple deaths
1863 -1863 - N20N20 reintroduced by Coltonreintroduced by Colton
1887 - The first1887 - The first anesthesia machineanesthesia machine - N20/02- N20/02
1953-1953- Fluorinated anestheticsFluorinated anesthetics
1954-1954- Halogenated drugs; HalothaneHalogenated drugs; Halothane (more pleasant(more pleasant
odor, higher potency, favorable pharmacokinetic,odor, higher potency, favorable pharmacokinetic,
nonflammability& low toxicitynonflammability& low toxicity))
1960:Enflurane,Isoflurane,desflurane,Sevoflurane1960:Enflurane,Isoflurane,desflurane,Sevoflurane
XenonXenon : inert gas ,under investigation: inert gas ,under investigation

10. History of AnesthesiaHistory of Anesthesia
Operation Under Ether -1852Operation Under Ether -1852
“The effect of the gaseous inhalation in neutralizing the
sentient faculty was made perfectly distinct to my mind..”
Massachusetts General Hospital, Boston

11. Anesthesia
Now covers :
1. OR
2. PACU
3. PREOP. CLINIC
4. RESP. CARE
5. ICU (gen.surg.,cardiac surg.,Tx.)
6. PAIN CLINIC (acute & chronic pain services)
7. OPIOD DETOXIFICATION
8. TRAUMA team
9. EMERGENCY DEPT.
10. CPCR

12. Types of Anesthesia
 Local Anesthesia: loss of sensory perception over a
small area of the body
 Regional Anesthesia: loss of sensation over a specific
region of the body (e.g. lower trunk)
 Monitored Anesthesia Care (MAC) :conscious sedation
+ observation & management of complications
 General Anesthesia: loss of sensory perception of the
entire body

13. General Anesthesia (defenition)
loss of response to & perception of all external stimuli
 Components of General Anesthesia:
1. Unconsciousness
2. Analgesia (most GA’s are poor analgesics)
3. Amnesia
4. Anexiolysis
5. Areflexia
6. Attenuation of autonomic responses to painful stimuli

14. Gas Volatile liquids* BarbituratesBarbiturates
Misc.
OpioidsOpioids
BenzodiazepinesBenzodiazepines
(nitrous oxide) (halothane
isoflurane,
desflurane,
sevoflurane)
(thiopental)
(midazolam)
(fentanyl)
(etomidate,
propofol)
General Anesthetics
Inhalational Parenteral

15.  Inhalation anesthesia
 Total intravenous anesthesia
 Inhalation plus intravenous (“Balanced
Anesthesia”)
Most common
Anesthetic Techniques

16.  Induction- initial entry to surgical anesthesia
 Maintenance- continuous monitoring and medication
 Maintain depth of anesthesia, ventilation, fluid balance,
hemodynamic control, hoemostasis
 Emergence- resumption of normal CNS function
 Extubation, resumption of normal respiration
Phases of General Anesthesia

17. Inhalation Anesthetics
 Gas enters the blood
plasma but rapidly
leaves it in preference
for a lipid environment
such as cell
membranes/ the brain
Inhaled and
exhaled gases
Inhaled and
exhaled gases
AveoliAveoli BloodBlood Tissues,
including
Brain
Tissues,
including
Brain

18. The “Old Theory” of General Anesthesia
Induction
Anesthetic molecules
partition into lipid bilayers
A non-specific miracle occurs….
Unconsciousness
Remove anesthetic
The exact opposite of the
non-specific miracle occurs….
Patient wakes up
(∆ cell lipid bilayer
physical properties?)
(some GA’s produce
stereospecific effects!?)

19.  Potentiation of
inhibitory ‘receptors’
 GABAA
 Glycine
 Potassium channels
 Inhibition of
excitatory ‘receptors’
 NMDA (glutamate)
 AMPA (glutamate)
 Nicotinic
acetylcholine
 Sodium channels
Receptors Possibly Mediating CNS
Effects Of Inhaled Anesthetics

20. Inhalation Anesthetics
Applying a gas rather than a solid or a liquid
special set of terms:
 Concentration –µg/litre or µM is possible but
difficult because of the volatility of the drug
MAC – minimum alveolar concentration (as a
percentage) to induce pain insensate anesthesia

21. Minimum alveolar concentration
 Alveolar concentration required to
prevent movement in 50% of
subjects in response to skin incision
 standard stimulus
 represents brain concentration
 consistent within and between
species
 additive
Agent MAC
Nitrous oxide 104
Desflurane 6.6
Sevoflurane 1.8
Enflurane 1.63
Isoflurane 1.17
Halothane 0.75

22. Factors increasing MAC
 Hyperthermia
 Chronic ETOH abuse
 Hypernatremia
 Increased CNS transmitters
 MAOI
 Amphetamine
 Cocaine
 Ephedrine
 L-DOPA

23. Factors decreasing MAC
 Increasing age
 Hypothermia
 Hyponatremia
 Hypotension (MAP<50mmHg)
 Pregnancy
 Hypoxemia (<38 mmHg)
 O2 content (<4.3 ml O2/dl)
 Metabolic acidosis
 Narcotics
 Ketamine
 Benzodiazepines
 α2 agonists
 LiCO3
 Local anesthetics
 ETOH (acute)
 And many more

24. Factors with no influence on MAC
 Duration of anesthesia
 Sex
 Alkalosis
 PCO2
 Hypertension
 Anemia
 Potassium
 Magnseium

25. Intravenous anesthesia

26. Intravenous Anesthetic Agents
 1656 : First attempt at intravenous anesthesia by
Wren -- opium into his dog
 1934 : Use in anesthesia with thiopental
 Many ways to meet requirements-- muscle
relaxants, opoids, nonopoids
 Appealing, pleasant experience

27. Narcotic agonists (opioids)
 Used for years for analgesic action-- civil war for
wounded soldiers
 Predominant effects are analgesia, depression of
sensorium and respirations
 Mechanism of action is receptor mediated

28. Muscle Relaxants
 Neuromuscular Junction

29. Local Anesthetics
 Mechanism of action is by reversibly blocking
sodium channels to prevent depolarization
 Anesthetic enters on axioplasmic side and
attaches to receptor in middle of channel

30. Anesthesia subspecialities
 Intensive care medicine
 Anesth. For thoracic surg.
 Anesth. For cardiac & vascular surg.
 Neurosurgical anesth.
 Organ transplant
 Anesth. For hepatobil. & genitourinary sys.
 Anesth. For OB & laparoscopic surg.
 Ped. & geriatric anesth.
 Anesth. For robotic & LASER surg.
 Anesth.for trauma
 Anesth. For Ophth. & ENT operations
 CPCR

31. Thank you!