general anesthesia-related to OMFS

1. Dr.Savita Sahu
Dept. of oral and maxillofacial surgery
SRI SIDDHARTHA DENTAL COLLEGE AND HOSPITAL

2.  INTRODUCTION
 HISTORY
 PREANESTHETIC PHYSICAL EVALUATION
 PREANESTHETIC PREPARATION
 ANESTEHTIC EQUIPTMENT
 PHARMACLOGY OF ANESTHESIA

3.  ANESTHESIOLOGY- (Greek Word)
 An-not, aisthesis- perception, logia- study.
 GENERAL ANESTHESIA- is a drug induced reversible state
of unconsciousness, during which patients are not
arousable, even by painful physical stimulation.
 The ability to independently maintain ventilatory function is
impaired.
 Patients often require assistance in maintaining a patent
airway, and positive pressure ventilation may be required,
because of depressed spontaneous ventilation or drug
induced depression of neuromuscular function.
Cardiovascular function may be impaired {ASA}

4.  BALANCED ANESTHESIA- it is a term used to describe the
multi drug approach to manage the patient needs.
 Includes the administration of medications preoperatively
for sedation and analgesia, the use of neuromuscular
blocking drug intraoperatively, and both i.v and inhale
anesthetic drug.
 Takes the advantage of drugs beneficial effects, while
minimising the adverse effect of each agent. Give greater
control to the anaesthesiologist.

5.  HORACE WELLS - administered the 1st GA for
dental extraction.
 GA was absent till mid 1800s.
 In 1846, William Morton successfully demonstrate
the properties of ether to facilitate the dental
extraction in Massachusettes.
 In 1860, Colton repopularised N2O.
 LA arrival was scientifically reported in 1884.
 Safe provision of GA in dentistry in dental clinics - 1990

6.  1. Medical history questionnaire
 2. Physical examination
 3. Lab investigations.
 4. Reasons of Pre-Anaesthetic evaluation

7. 1. Current problems.
2. Other known problems.
3. Treatment/medicines for the problems: dose, duration
and effectiveness.
4. Current drugs use: reason, dose, duration, effectiveness
and side effect.
5. History of drug allergies.
6. History of use of tobacco—smoking or smokeless tobacco
or alcohol consumption, frequency, quantity and duration.
7. Prior anaesthetic exposure: type and any adverse effects.
8. General health and review of organ systems.

8.  L- look for facial abnormality.
 E- evaluate 3-3-2
 M-Mallampati grade
 O-obstruction
 N- neck mobility
Mshelia DB, Ogboli-Nwasor EO, Isamade ES. Use of the “L-E-M-O-N” score in predicting
difficult intubation inAfricans. Niger J Basic Clin Sci 2018;15:17-23.

9.  INTRA ORAL EXAMINATION-
To minimise the dental injury during intubation
following steps should be taken.
 Assessment of patient’s dentition
 Intraoral tissues examination
 Dental history
 Specific discussion about any existing dentures or crowns;
particularly of the patient’s maxillary incisor
Guruprasad Y. Preanesthetic dental evaluation for dentofacial injuries to be managed under general
anesthesia. Med J DY Patil Univ 2016;9:229-30

10. THE DIFFICULTY OF MASK VENTILATION-
 Common risk factors include a body mass index (BMI) of more
than 30 kg/m2,
 Male sex,
 Presence of a beard,
 High Mallampati classification,
 Snoring,
 Decreased thyromental distance,
 Head and neck radiation
James Cphero et al,Adult Airway Evaluation in Oral Surgery, Anesthesia:Oral and Maxillofacial clinics of North
America; Volume 25, Issue 3, Pages 341-536 (August 2013)

11. GRADING THE DIFFICULTY OF TRACHEAL INTUBATION
 Cormack, Lehane-classifications determined by the view
obtained at laryngoscopy

12.  Cormack, Lehane-classifications-modified by Yentis and Lee.

13. ANATOMIC CONSIDERATIONS
 Atlanto-occipital mobility,
 Mouth opening
 dentition,
 mandibular space
 Thyro-mental distance
 Visibility of Oropharyngeal Structures
James Cphero et al,Adult Airway Evaluation in Oral Surgery, Anesthesia:Oral and Maxillofacial
clinics of North America; Volume 25, Issue 3, Pages 341-536 (August 2013)

14.  ATALANTO-OCCIPITAL MOVEMENT
 GRADE I->35
 GRADE II-22-34
 GRADE III- 12-21 difficult laryngoscopy
 GRADE IV-<12
James Cphero et al,Adult Airway Evaluation in Oral Surgery, Anesthesia:Oral and Maxillofacial clinics of
North America; Volume 25, Issue 3, Pages 341-536 (August 2013)

15. MALLAMPATTI CLASSIFICATION

16.  THYROMENTAL DISTANCE

17.  STERNOMENTAL DISTANCE
A A SMD ≤ 13.5 cm is
considered cm is considered
predictive of difficult
laryngoscopy

18.  MAXIMUM VERTICAL MOUTH OPENING
Most people
can open their mouth 35
to 55 millimeters (1.4 to
2.2 inches), which is
about the width of 3
fingers

19.  AIRWAY MANAGEMENT-
SUPRAGLOTTIC AIRWAY MANAGEMENT-
1) LARYNGEAL MASK AIRWAY-
size 3-4 for women
4-5 for men.
Cuff is passed on following the curvature of the tongue
followed by inflation with 20-30 ml of air

21. 2) ESOPHAGEAL OBTURATOR AIRWAY- blind insertion results in
tube entering the oesophagus.
Ventilation of the airway occurs through the 8 holes in the
tube.
DISADVANTAGE - inability to administer drug in bronchus
- obstruction of hole by mucus.
Rarely used in hospitals.

22.  1)NASOTRACHEAL INTUBATION-
There are two pathways along which a
tube can be introduced through
the nasal cavity namely the
lower and upper pathway.
 Lower pathway is preferred.

23.  The cuff is usually inflated to 25 mm
of Hg which is also called ‘‘just seal volume’.
There are 2 type of tube –
Magil and Murphy eye tube.

25.  2) SUBMENTAL INTUBATION-
types include
 The submental route for tracheal intubation was first
introduced by Sir Hernandez Altemir in 1986
 Altemir sequence- involves a single endotracheal tube that is
exteriorized through the submental dissection plane.
 Green and Moore sequence’- involves two endotracheal tubes
whereby the first oral tube is replaced by a second tube
introduced through the submental tunnel
 J.S.Jundt, D.Cattano, C.A.Hagberg, J.W.Wilson: Submental intubation: a literature review. Int. J. Oral Maxillofac. Surg.
2012; 41: 46–54.

26.  SUBMENTAL INTUBATION-
 patient position on the operating table,
 a 2 cm long skin incision was made in the submental region,
2 cmfrom the midline, and 2 cm medial to and parallel with
the mandible– following the so called “2-2-2 rule”

27.  Incision of the platysma , and investing layer of the deep
cervical fascia is given.
 curved forceps were used to perform blunt dissection in
the lingual surface of the mandible, penetrating the floor of
the mouth for creation of a tunnel.
 The proximal end of the endotracheal tube was withdrawn
from the oral cavity.
 And the tube is secured with sutures

29.  SUBMANDIBULAR APPROACH
 a 1.5 cm incision is made through the skin in the anterior
submandibular region and , parallel to the inferior border of
the mandible – this is to avoid injury to the marginal
mandibular branch of injury to facial nerve

30.  a blunt dissection is performed through the platysma, the
deep cervical fascia and mylohyoid muscle
 Creating a tunnel in close proximity to the lingual cortex of
the mandible to prevent injury to the ducts of the lingual
and submandibular salivary glands.
 The pilot balloon is pulled out first, then the proximal end
of the orotracheal tube is grasped, exteriorized and secured
to skin

32.  Difficulty in intubation
 It is over come by
 -Manipulation of the thyroid cartilage
 -Use of gum elastic bougie,60 cm long(it is inserted into the
Trachea and over which the tube is railroaded into place)
 -Use of fibreoptic bronchoscope

33.  Fiberoptic laryngoscopy :
 The flexible fiber optic laryngoscope ,bronchoscope or
rhinoscope is used for tracheal intubation
 Patient is conscious during the procedure, so that vocal
folds can be observed during phonation
 Other available fiber optic devices include the Bullard
scope ,upsher scope and wuscope, usually used in
setting of difficult intubation.

34.  Video laryngoscope:
 It employ digital technology such as complementary
metal oxide semiconductor, active pixel sensor (CMOS
APS) to generate a view of the glottis ,so that the
trachea may be intubated.

35. 1) i.v benzodiazepine– for sedation
2) Topical anesthetic –cocaine applied to each nostril if
intubating nasally
3) 100% Oxygen 5-7LPM given.
4) Propofol is then given until patient looses consciousness.
5) Airway patency is checked .
6) Succinylcholine is given Depolarising muscle relaxant.
7) if fasciculation is there and pt. stops breathing the non
depolarising muscle relaxant is given

36. 8) Nasotracheal or other intubation is performed
9) Then tube is attached to anesthetic machine and pt. is
intubated.
10)Maintainces drug like propofol or meperidine is given.
11)Gas flow is adjusted to 3LPM of N2O and 2LPM of O2.
12) endotracheal tube is secured, the cuff is inflated(
confirmation is done by auscultating the chest )
13) Patient is draped, vitals monitered and
14) Maintainces dose is give

37. 15) Lignocaine is given
16) Ocassionaly additional muscle realxant like vecuronium or
atracurium

38.  RADIOLOGICAL EVALUATION OF AIRWAY-
 White and Kander found that greater posterior depth of the
mandible, seen as difficult laryngoscopy (DL)
 Mandibular measurements like longer mandibulohyoid
distance, shorter length of mandibular ramus, effective
mandibular length (measured from tip of lower incisors to
temporomandibular joint) less than 3.6 times the posterior
depth of mandible, greater posterior depth and anterior
depth of the mandible and increased mandibular angle
suggest DI.
 Jain K, Gupta N, Yadav M, Thulkar S, Bhatnagar S. Radiological evaluation of
airway – What an anaesthesiologist needs to know!. Indian J Anaesth 2019;63:257-
64

39.  A. COMMON HAEMATOLOGICAL INVESTIGATIONS
1)HEMOGLOBIN- male- 12-14 g%
female- 10-12g%
2) Complete blood count-
A). RBC-male- 4.5-6.2 million/cumm
female -4.5-5.5 million/cumm
B). WBC- 5000-10000/cumm
C). DLC- neutrophilis-50-62%
eosinophils- 2-8%
monocytes-1-3%

40. lymphocytes-25-30%
basophilis- 0-1%
Platelets- 1.5-4 lakhs/cumm
3) ESR- males- 17yrs-50yrs 10mm
> 50yrs 12-14 mm
females->50yrs 19-20mm
4) MCV -85+/- 8fl
5) MCH- 29.5+/- 2.5pg
6) MCHC- 32-5+/- 2.5g/dl

41.  B ) LIVER FUNCTION TEST
o bilirubin- conjugated- 0.1-0.3 mg%
- unconjugated-0.2-0.7 mg%
o Alanine transaminase – 0-48I.U/L
o Aspartate transaminase-male-10-55.I.U/L
female-7-30.I.U/L
o Gamma glutamate- female-5-29U/L
male -5-38 U/L
o Serum Protein- 6-8 g%
o Serum gloubin- 2.5-3.5 g%
o Serum albumin-4.0-5.7 g/dl

42.  C) KIDNEY FUNCTION TEST-
 1) serum creatinine- male- 0.7-1.5 mg%
female- 0.5-1.2 mg%
(more sensitive indicator of GRF than BUN).
2) Serum potassium- 3-5mE/L
3)Serum sodium- 136-145 mEq/L
4)Serum urea- 18-40mg %

43. D) OTHER BIOCHEMICAL INVESTIGATIONS-
1. Serum calcium-9-11mg/dl
2. Ionized calcium-1.1-1.4 mmol/L
3. Serum phosphate-children- 4.5-6.5 mg/dl
adult- 3.0-4.5 mg/dl.
1. Acid phosphate- 0-0.8 U/L
2. BLOOD GLUCOSE- RBS-80-140mg/dl
FBS-70-110mg/dl
PPBS-<140MG/DL

44. E) COAGULATION PROFILE-
1. Bleeding time- 3-8 mins
2. Clotting time- 9-14 mins
3. Prothrombin time (PT)- 12-15sec
4. Partial prothrombin time (PPT)-30-40 sec.
5. Thrombin time- 10-12 sec
6. International normalised ratio – normal- 1

45.  BASIC PLAN FOR PREANESTHETIC PREPARATION INCLUDES-
1. Patient counselling
2. Premedication
3. Preoperative instruction

46. RELIEF OF ANXIETY
AND APPERHENSION
PREOPERATIVELY
SMOOTH
INDUCTION
SUPPLEMENT AND
POTENTIATE
ANAESTHETIC ACTION
DECREASE SECRETION
AND VAGAL
STIMULATION
ANTIEMETIC EFFECT
DECREASE ACIDITY
AND VOLUME OF
GASTRIC JUICE
AIMS

47.  PRE ANESTHITIC MEDICATIONS
PSYHOLOGICAL COUNSELLING
• Explain the procedure in simple language .
• Explain them what to expect
PHARMACOLOGICAL METHOD
• Various drugs

48. 1. BENZODIAZEPINES- it is a sedative hypnotics, reduces
anxiety, provides amnesia
Classification
1. SHORT ACTING – midazolam
2. INTERMEDIATE ACTING- lorazepam, temazepaM
3. LONG ACTING- Diazepam

49. MIDAZOLAM :-
 It is 3 to 5 times more potent than diazepam
 When given im the onset of action seen within 5-10 min,
with peak effect seen in 30-60min
 Dosage :
 Intramuscular : 0.07-0.15 mg/kg
 Intravenous :0.03-0.05mg/kg , 2 to 5 mg in 0.5mg
increments till desired effect is seen
 Intranasal :0.3-0.4mg/kg
 Oral :sublingual 0.5-0.7mg/kg
 Rectal :0.5-0.75mg/kg

50.  DIAZEPAM :
 Considered as ‘gold standard with other drugs
 It has anxiolytic ,amnestic and sedative effects
 Oral dose absorbed in 30-60min in adults and 15-30 min in
children
 It is dissolved in organic solvent , hence it causes pain on IV
and IM injection
 Oral diazepam is usually administered night prior to the
surgery for anxiolysis
 Dose:
 Oral :0.2-0.5mg/kg
 Intravenous :0.04-0.1mg/kg

51.  2. ANTICOLENERGIC- drugs which decrease secretion, vagal
stimulation caused by anaesthetic drugs and prevents
largyospasm by decreased secretion of larynx.
Anticholenergic
Antimuscarinic Antinicotinic
1 ganglionic blocker
2. Neuromuscular blocker

53. ATROPINE GLYCOPYROLATE SCOPOLAMIE
Tertiary ammonium
compound
Quaternary ammonium
compound
Quaternary
ammonium
compound
Dose 0.01-0.02mg/kg 0.005-0.01mg/kg
Onset 1min 1min
Lasts for 3hrs 6hrs
Heart rate +++ ++ +
Inhibition on
sweating
+++ ++( body temp. no
affect)
+
GLYCOPYROLATE has selective peripheral action, acts rapidly
longer acting.
BUT, atropine is preferred for vagal mediated bradycardia ,
preferred in children.

54.  3. ANTIEMETIC- An empty stomach reduce the risk of
regurgitation and aspiration of gastric juice.
A. 1- 5HT3 antagonist- ondansetron, grainsetron.
B. 2- centrally acting- metachlopramide, domperidone,
chlorpromazine
C. 3- h1 receptor antagonist- promethazine, cyclizine,
diphenramine.
D. 4- anticholineric (muscarnic receptor blocker)- hyoscine,
scopolamine.

55. 4. DRUG REDUCIND ACID SECRETION
A. RANITIDINE-(150-300mg)- given night before and morning
along and reduces risk of gastric regurgitation.
B. PROTON PUMP INHIBITOR- omeprazole(20 mg).
C. SODIUM CITRATE- It is a non particulate antacid given 15-
30 min before induction raises gastric PH to >2.5 but,
disadvantage is that increase volume of gastric juice
D. METOCLOPROMIDE-it is a procainamide derivative , its an
D2, 5HT3 antagonist.

56.  PRE ANESTHITIC PREPARATIONS-
 1. FASTING GUIDELINESS
INJESTED MATERIAL MINIMUM FASTING PERIOD
Clear fluid 2 hrs
Breast milk 4 hrs
Non human milk 6 hrs
Infant formula feed 6 hrs
Light meal 6 hrs
Heavy meal 8 hrs

57.  2. LIGNOCAINE ALLERGY TEST-
Done before 2-3 hrs of treatment
Percutaneous – intradermally (1:100 dilution lignocaine) to
raise a belb of 1mm
Uneventful--- 20 mins later
Raise 1 mm belb using 1:10 solution of 1% lignocaine
Uneventfull---
1ml of undiluted lignocaine inj. subcutaneously

58.  A positive test means wheel associated with erythema of
greater than 1 cm.
 Each response is evaluated 20 mins of dose
 DISADVANTAGE- this test dose not exclude allergy due to
preservative
 3 PATIENTS PARTS PER PREPARATION-
 Bath
 Clothing
 Preparation of parts- shaving 12hrs prior
-scrub
-parts painted with 2% picric acid &
covered

59. 4.PREPARATION OF ORAL CAVITY-antiseptic mouthwash
5.PARTS PREPARATION - preoperatively as well as intra
operatively-
Area is scrubbed vigorously using a sterile swab forceps with no
touch technique with antiseptic soap solution for 2 mins
Clean with dry sponge or sponge soaked in saline
Area is painted with 5% povidone iodine ( keep for 2 mins)
70% alcohol with continuous contact for several mins.
adjacent area is draped to prevent cross contamination

60. 5.INJECTION T.T. IS GIVEN
6.INJECTION Diclofenac Sodium/Potassium 75MG GIVEN
7.INJECTION TAXIM IS GIVEN

61. 1. Anesthetic machine
2. Breathing system circuit
3. Anesthetic mask
4. Laryngoscope
5. Endotracheal tube
6. Laryngeal mask airway
7. Magil forceps
8. Mouth prop
9. Bite block
10. Resuscitation bag

63. 1. Blood pressure monitor
2. Cardioscope
3. Pulse oximetry
4. Capnometer/capnographs
5. Respiratory gas monitor

64. 1. Oxygen cylinder
2. Oxygen flowmeter
3. Oxygen mask
4. Nasal catheter or prongs

65. 1. Scalp needle
2. Intravenous canula
3. Bivalve
4. Infusion set
5. Intravenous fluid
6. NEWER ADVANCES INCLUDES
7. Fiberolaryngoscope,video laryngoscope

66.  INTERMITTENT – Gas flows only during inspiration. Eg:
Entonox apparatus, Mackessons apparatus
 CONTINOUS – Gas flows both during inspiration &
Expiration. Eg. Boyles Machine

67.  System Components
• MASTER SWITCH
• POWER FAILURE INDICATOR
• RESERVE INDICATOR
• ELECTRICAL OUTLET
• CIRCUIT BREAKER
• DATA COMUNICATION PORT
ELECTRICAL
• HIGH PRESSURE SYSTEM
• INTERMEDIATE PRESSSURE SYSTEM
• LOW PRESSURE SYSTEM
PNEUMATIC

68.  Gwathmey and Marshal had developed their machines
before, but all the credit had gone to Boyle.
 The machine performs four essential functions:
1. Provides O2,
2. Accurately mixes anaesthetic gases and vapours,
3. Enables patient ventilation and
4. Minimises anaesthesia related risks to patients and staff
Gurudatt CL. The basic anaesthesia machine. Indian J Anaesth 2013;57:438-
45.

69.  The anaesthesia machine can be conveniently divided into
three parts:
 (a) The high pressure system,
 (b) the intermediate pressure system
 (c) the low pressure system

70. High pressure

71.  The high pressure system consists of all parts of the
machine, which receive gas at cylinder pressure. These
include the following
A. The hanger yoke
B. The yoke block,
C. The cylinder pressure gauge
D. The pressure regulator

72.  The body,
 the retaining screw
 the gasket
 the index pins
 the Bodok seal- form a seal between
the cylinder and the yoke
 a filter
 the check valve assembly

73.  THE INTERMEDIATE PRESSURE SYSTEM -It includes the
components of the machine which receive gases at reduced
pressures usually 37-55 PSIG.
 O2 FLUSH
 THE FLOW METER ASSEMBLY

74.  LOW PRESSURE SYSTEM
A. Vaporizers mounted on the back bar
B. back pressure safety devices
C. The common gas outlet.

76. Inhalation agent
Gases liquid
N2O CHLOROFORM
Entox ether
Xenon halothane
enflurane
isoflurane
sevoflurane
Intravenous agent
1)Inducing agent 2) benzodiazepine
diazepam
Proprfol lorazepam
Thiopentane midazolam
Etomidate 3)dissociative
ketamine
4)neurolept analgesia
fentanyl

77.  Anaesthetic vapours are mixed with carrier and delivered to
patient during anaesthesia .
 It is carried via respiratory passage to the alveoli, and
blood, to the brain.

78.  The inhalational anaesthetic agents are small lipid soluble
molecule that cross the alveolar membrane easily. Move
into and out of the blood based on partial pressure
gradient.
 FACTORS AFFECTING THE PARTIALPRESSURE OF ANSTHETIC
IN BRAIN ARE-
 1) Partial pressure of anaesthetic in inspired gas
 2) Pulmonary ventilation
 3) Alveolar exchange-
 4) Solubility of anaesthetics in blood – determined by blood
gas partition coefficient.
Blood ↓ the ratio ↑the conc. In brain
gas

79.  5)solubility of anesthetic in fat oil/gas solubility-
 Lipid solubility - correlates strongly with the potency of the
anesthetic.
 6) cerebral blood flow.

80.  SECOND GAS EFFECT
 The ability of the large volume uptake of one gas (first gas)
to accelerate the rate of rise of the alveolar partial
pressure of a concurrently administered companion gas
(second gas) is known as the second gas effect.
 Ex-Halothane (1%) & N20:O2 ( 75%: 25%)

81.  DIFFUSION HYPOXIA-N2O has low blood solubility, rapidly
diffuses into alveoli and dilutes alveolar air- PP of oxygen in
alveoli is reduced, resulting in hypoxia called as diffusion
hypoxia.
 Prevented by giving 100% oxygen for few mins, after
discontinuing N2O.

82.  Modern theory on Mechanism of General Anaesthesia.
 Mainly acts via interaction with membrane proteins
 Different agents - different molecular mechanism
 • Major sites: Thalamus & RAS, Hippocampus and Spinal
cord
 • Major targets – ligand gated ion channels
 •Important one – GABAA receptor gated Cl¯ channel
complexes; examples – many inhalation anaesthetics,
barbiturates, benzodiazepines and propofol – Potentiate the
GABA to open the Cl¯ channels – Also direct activation of Cl¯
channel by some inhaled anaesthetics and Barbiturates

83.  Receptor sits on the membrane of its neurone
at the synapse
 GABA, endogenous compound, causes GABA
to open
 Drugs (GA) don't bind at the same side with
GABA
 GA receptors are located between
an alpha and beta subunit

84.  Structure of GABAA
 GABAA receptors – 4 transmembrane (4-TM) ion channel
 – 5 subunits arranged around a central pore: 2 alpha, 2
beta, 1 gamma
 Each subunit has N-terminal extracellular chain which
contains the ligand-binding site
 4 hydrophobic sections cross the membrane 4 times: one
extracellular and two intracellular loops connecting these
regions, plus an extracellular C-terminal chain.

85.  Normally, GABAA receptor mediates the effects of
gamma-amino butyric acid (GABA), the major inhibitory
neurotransmitter in the brain
 – GABAA receptor found throughout the CNS most
abundant, fast inhibitory, ligand-gated ion channel in
the mammalian brain located in the post-synaptic
membrane.
 Ligand binding causes conformational changes leading
to opening of central pore and passing down of Cl-
along concentration gradient. Net inhibitory effect
reducing activity of Neurones
 General Anaesthetics bind with these channels and
cause opening and potentiation of these inhibitory
channels – leading to inhibition and anaesthesia.

86.  Other Mechanisms:
 Glycine – activates Cl¯ channel in spinal cord and medulla-
Barbiturates, propofol and others inhalation anaesthetics.
 N – methyl D- aspartate (NMDA) type of glutamate receptors
- Nitrous oxide and ketamine selectively inhibit.
 Inhibit neuronal channels gated by nicotinic cholinergic
receptors – analgesia and amnesia (Barbiturates and
fluorinated anaesthetics.)

87. Minimum alveolar concentration-(MAC)-
 Measure of potency of inhalational anaesthetic.
 It is defined as the minimum alveolar anaesthetic
concentration ( % of the inspired air) at which 50% of
patients do not respond to a surgical stimulus eg a akin
incision.
 Greater the MAC lower the anaesthetic potency.

88.  FACTORS AFFECTING MAC-
 1) Temperature- MAC ↓ with ↓ body temperature
 2) Effect of pressure- ↑ in hydrostatic pressure ↑ MAC
 3) Effect of age- > 6 month MAC ↑
MAC ↓ with age
 N2O has maximum MAC-104.
 Methoxyflurane has least MAC -0.16.

89. 1. OPEN DROP METHOD-
 Liquid anaesthetic is poured over a mask with a gauze. The
vapour is then inhaled.
 DISADVANTAGES
 Vapours escape to the surroundings
 The amount of anaesthetic concentration
breath by the patient cannot be determined.

90. 2. THROUGH ANESTHETIC MACHINE
a). OPEN SYSTEM
A. Exhaled gases are Allowed to escape
B. Fresh anaesthetic mixture is drawn in each time.
C. No rebreathing is allowed
D. Flow rate is high
E. More drug is consumed
 ADVANTAGES
 Predetermined oxygen & Anaesthetic concentration Can
be accurately delivered.
 Used mostly for paediatric cases
Parthasarathy S. The closed circuit and the low flow systems. Indian J Anaesth 2013;57:516-24.

91. b). CLOSED SYSTEM
 The patient rebreathes the exhaled gas. The mixture is
circulated through sodalime
 It absorbs the carbon dioxide
 Flow rates are slow
 ADVANTAGES-It is useful for expensive and explosive
agents as little anaesthetic escape the environment.

92.  SODA LIME Mechanism of function
 Mixture of calciumoxide(90%),sodium hydroxide(5%)
 And potassium hydroxide(1%)
 Water is also present in the granules
 CARBON DIOXIDE+SODIUM HYDROXIDESODIUMCARBONATES
+
CALCIUMHYDROXIDE
CALCIUM CARBONATE
 One of the commonly used
preparation changes from pink to white
 When the soda lime get exhausted

93. c). SEMICLOSED SYSTEM
 Partial rebreathing through a closed valve
Intermediate flow rates

95.  PHASES OF GA
 INDUCTION- time of onset after administration of GA to
development of surgical anaesthesia
 MAINTAINCES – sustaining the state of GA
 RECOVERY- stoppage of GA and gain of consciousness

96.  GAs depress the CNS
 in the following order:
 1st – cerebral cortex
 2nd – subcortex
 3rd – spinal cord
 4th – medulla oblongata
1
2
3
4

98. (diethyl ether)
 Spontaneously explosive
 Irritant to respiratory tract
 High incidence of nausea and vomiting during induction and post-
surgical emergence.
 Guedel described four stages of anesthesia with the help of ,
ether.
 Clearcut stages are not seen not a days

99. Stage of
Analgesia
• Starts from beginning of anaesthetic inhalation and lasts
upto the loss of consciousness
• Pain is progressively abolished
• Reflexes and respiration remain normal
• Use is limited to short procedures
Stage of
delirium
• From loss of consciousness to beginning of regular
respiration
• Patient may shout, struggle and hold his breath; muscle
tone
• Increases, jaws are tightly closed, breathing is jerky;
vomiting,
• involuntary micturition or defecation may occur
• Heart rate and BP may rise and pupils dilate due to
sympathetic stimulation
• No operative procedure carried out
• Can be cut short by rapid induction, premedication

100. Surgical
Anaesthesia
• Extends from onset of regular respiration to cessation
of spontaneous breathing.
• This has been divided into 4 planes which may be
distinguished as:
• Plane 1 rolling eye balls. This plane ends when eyes
become fixed.
• Plane 2 loss of corneal and laryngeal reflexes.
• Plane 3 pupil starts dilating and light reflex is lost.
• Plane 4 Intercostal paralysis, shallow abdominal
respiration, dilated pupil.
Medullary
Paralysis
• Cessation of breathing to failure of circulation and
death.
• Pupil is widely dilated, muscles are totally flabby,
pulse is thready or
• imperceptible and BP is very low

102.  Manufactured by heating ammoniumnitarte in an iron rote
at a temp of 240◦C.
 NH4NO3= 2H2O + N20
 It is sweet smelling, non irritating, colourless,
noninflamable and tasteless
 Weak anaesthetic, potent analgesic.
 Dose not depress respiration,
 No cardiovascular effect
 Can cause bone marrow depression.

103.  SECOND GAS EFFECT-N2O can concentrate the halogenated
anaesthetic in the alveoli, when they are concomitantly
administered , because of its first uptake from alveolar gas.
 DIFFUSION HYPOXIA -rapid outpouring of insoluble N2O can
displace alveolar oxygen, resulting in hypoxia.
 All patient should receive o2 supplement at the end to prevent

104.  ZONES OF N2O- four zones of anesthesia have been
described
 1). MODERATE ANALGESIA (6%-25%) 25% is more potent than
10mg of morphine.
 2). DISSOCIATIVE ANALGESIA (26%-45%)- gives psychological
symptoms.
 3). ANALGESIA ANESTHESIA (46%-65%)- complete analgesia
 4). LIGHT ANESTHESIA (66%-80%)- complete analgesia and
amnesia.

105.  2-bromo-2-chloro-1,1,1-trifloroethane
 Non flammable, non explosive.
 Pleasant smell, non irritating.
 Induction 2-4 %
 Maintanence 1-2%.
 BP falls in proportion to the vapour inhaled.
 Depression of respiratory centre.
 Respiratory rate increases, depth of respiration decreases

106.  Mild relaxation of skeletal muscle.
 Pharyngeal and Laryngeal reflexes are abolished, coughing
is suppressed.
 Urine formation is decreased due to low GFR.
 Less post operative nausea and vomiting.
 About 20% is metabolized in liver, rest is exhaled out.
 Malignant Hyperthermia can occur in susceptible
individuals.

107.  Synthesized in 1965 by terrell, introduced into practice in
1984
 Cheap and widely used
 Highest oil gas partition cofficient (90.8)
 Non carcinogenic, nonflammable,pungent
 Less soluble than halothane.
 It can cause coronary artery vasodilatation
 Depresses respiratory drive and ventilatory responses
 Myocardial depressant-less than halothane

108.  Excellent muscle relaxant- potentiates effects of
neuromuscular blockers.
 Bronchoirritating, laryngospasm
 Pungent smell – not good induction agent

109.  Volatile anesthetic is a non-flammable
fluorinated variant of Isoflurane
 Lowest oil-gas coefficient (18.7)
 Very fast action (on and off) makes it a great
choice for outpatient anesthesia.
 Induction by using 6 to 10 % desflurane in air
or in oxygen, or by using 5 to 8 % desflurane
in 65 % nitrous oxide
 Maintenance with 5 to 7 % desflurane

110.  As higher conc. Are used, may irritate air passage, and
induce coughing.
 Pungent smell-not suitable for induction.
 Degree of respiratory depression and fall in B.P, similar to
isoflurane.
 Exhaled unchanged and more rapidly

111.  Does not irritate the airway. Has low
solubility in blood ,so used for rapid
induction without intravenous anesthetics
 Induction by using 1.5 to 3 % sevoflurane in
air or in oxygen, or by using 0.7 to 2 %
sevoflurane in 65 % nitrous oxide.
 Maintenance with 0.4 to 2 % sevoflurane.
 Expensive

113.  Highly soluble in water yielding an alkaine solution.
 Extravasation or intra-arterial injection produces intense
pain.
 Dosage- 3-5 mg/kg. acts in 15-20 sec.
 Elimination- 8-12hr.
 It is weak muscle relaxant, poor analgesic, dosenot irritate
air passage.

114.  Decreases blood pressure due to vasodilation.
 Respiratory depression, can lead to bronchospasm.
 Occasionally used for rapid control of convulsions Dose
dependent suppression of CNS activity
 Contraindicated: porphyria , status asthematicus

115.  It is an ideal induction agent
 Oily liquid employed as 1% emulsion.
 Unconsciousness occur in 15-45 sec and lasts for 5-10 min.
elimination is 100 min.
 Dosage- induction-1 to 2.5mg/kg.
 Maintainces- 25-100mg/kg.
 SIDEEFFECT-Amnesia
intracranial pressure decreases
pain on injection.
 Profound depression of upper airway reflexes.

116.  Direct CNS depressant (thiopental) and GABA agonist
 Lipid soluble. Pain on injection.
 Dose- 0.2-0.3mg/kg
 Minimal cardiac and respiratory effect.
 Anti epileptic
 Post op nausea and vomiting.

117.  Produce sedation and amnesia
 Potentiate GABA receptors.
 Onset of action is 30-60 secs.
 Duration of action 50-80mins.
 Dose- Premedication-0.04-0.08mg/kg
 Induction- 0.1-0.3mg/kg IV

118.  Minimal depression of cardiac and respiratory system.
 Decreases intra cranial pressure, causes anterograde
amnesia.
 Dependence- onset of physical or psychological symptoms
after reduction of dose.
 Overdose- treated by giving Flumazenil – 0.01mg/kg upto
0.2mg . IV

119.  Short acting Opioid.(30-50mins)
 Potent analgesic.
 Minimal cardiac effects-- no myocardial depression
 Marked respiratory depression.
 Tone of chest muscles may increase after rapid fentanyl
injection, muscle relaxant is required
 Dose-2-4μg/kg
 Repeated dose may be required every 30 mins.
 Side effects nausea, chest wall rigidity, seizures,
constipation, urinary retention

120.  It is a phenycyclidine derivative.
 It alters patients awareness about the surrounding.
 It induces dissociative anaesthesia characterised by stage of
sedation, immobility, amnesia, and marked analgesia.
 Dissociation produced in 15 sec, pt. becomes unconscious in
30 sec.
 Unconsciousness till 10 -15 min.
 Analgesia for 40-45 min.
 It causes increased secretion,

121.  It preserves the laryngeal and pharyngeal reflexes.
 Associated with hallucination, disagreeable dreams,
delirium and excitement during recovery.
 DOSAGE- acc. To weight
Upto 50 lbs-0.5-1 mg/ld
50-100lbs- 1.0-1.5 mg/lb
Above 100 lbs- 1.5 mg/lb +NaO:O2.
It os found safe in patient with minor oral surgical procedure.
C/I-pt. with hypertension, psychiatric pt, glaucoma

122.  NONDEPOLARIZING DEPOLARISING
 1. Long acting -Succinylecholine
 -pancuronium -decamethoium
 - tubocurarine
 2.Intermediate acting
 - vecuronium
 3.Short acting
 - mivacurium

123.  DURING ANESTHESIA
 1)respiratory depression and hypercarbia
 2)salivation, respiratory secretion
 3)cardiac arrhythmia
 4)fall in B.P.
 5)aspiration of gastric
 6)Laryngospasm
 7)awareness
 8)delirium, confusion
 9) fire and explosion

124.  AFTER ANESTHESIA
 1)Nausea and vomiting
 2)persisting sedation
 3)pneumonia, atelectasis
 4)organ toxicity
 5)nerve palsies
 6)emergence delirium
 7)cognitive defects

125.  MALIGNANT HYPERTHERMIA
 Hypermetabolic syndrome occurs in genetically susceptible
patients when exposed to anaesthetic triggering agents.
 Triggering agents- Halothane, Isoflurane, Desflurane,
Sevoflurane, Succinylcholine.
 The syndrome is thought to be due to reduction of
reuptake of calcium ions by sarcoplasmic reticulum leading
to sustained muscle contraction.
 This results in signs of hyper-metabolism like tachycardia,
acidosis, hypercarbia, hypoxemia and hyperthermia.

126.  Treatment
 Discontinue all anaesthetics agents.
 Administer Dantrolene 2.5mg/kg IV. And repeat to a total of
10 mg/kg.
 Hyperkalaemia to be corrected by Insulin and glucose
 Cold sponging
 Monitor urinary output

127.  POST OPERATIVE NAUSEA AND VOMITING
 CAUSES-
 Female gender
 Obesity
 Pregnancy
 Abdominal distention
 Premeditations- opioids, NSAID’s
 Anaesthetics- ether, nitrous oxide.
 Presence of pain, hypoxia, hypotension, hypoglycaemia in
post op period

128.  Treatment
 Underlying cause
 Supine position
 Antiemetic-
 Promethazine 12.5-25mg IM/IV(antihistaminic)
 Metoclopramide 10-20 mg orally.
 Ranitidine 50 mg IV
 Sodium citrate 30-60ml orally

129.  The strategy of lowering the patient’s blood pressure or
controlled hypotension during anesthesia is called as
(hypotensive anesthesia).
 Reducing the patient’s blood pressure during surgery can
potentially reduce overall bleeding making the surgical field
more clean of blood.

130.  INDICATIONS-
 spinal surgery,
 Hip or knee arthroplasty,
 craniosynostosis,
 hepatic resections,
 robotic surgery, and
 major maxillofacial operations.
 Associated risk – decreased perfusion to vital organs

131.  Mean arterial pressure (MAP) is reduced by 30%.
 Consequently, the systolic blood pressure values are about
80–90mmHg and the MAP is reduced to 50–65mmHg.
 Study conducted to find the difference in surgical field
conditions in major maxillofacial operations in hypotensive
and normotensive anesthesia found that the surgical field
conditions are better under hypotensive anesthesia and
there is no difference in the durations of the procedures

132.  PROTOCOLS FOR HYPOTENSIVE ANESTHESIA-
 A) Deep anesthesia and heavy analgesia
 B) administration of hypotensive drug.
 Volatile Anesthetic Agents- isoflurane
sevoflurane
desflurane
 when volatile anesthetics are used alone, high
concentrations are required to achieve a significant
reduction in intraoperative bleeding, and these
concentrations may lead to hepatic or renal injury.

133.  HYPOTENSIVE DRUGS-sodium nitroprusside (SNP),
1.nitroglycerin (NTG),
2.trimethaphan,
3.calcium channel antagonists (e.g., nicardipine),
4.𝛽-adrenoceptor antagonists (e.g., propranolol and esmolol),
angiotensin converting enzyme
5.(ACE) inhibitors,
6. 𝛼2- adrenoceptor agonists (e.g., clonidine and
dexmedetomidine).
 In addition to these agents, fenoldopam, adenosine, and
alprostadil are new hypotensive drugs, which are currently
being evaluated.

134.  NONPHARMACOLOGICAL MEANS FOR ACHIEVING
HYPOTENSION
 The Anti-Trendelenburg Position-depends on patients
cardiac out put
 Acute Normovolemic Hemodilution-accomplished by
drawing a unit or two of the patient’s blood either
immediately before or shortly after the induction of
anesthesia and simultaneously replacing it with a cell-free
fluid, preferably a synthetic colloid solution

135.  Type of Maxillofacial Operation-
 Le Fort osteotomies,
 maxillectomy for tumor resection,
 tumor resection from the tongue and, floor of the mouth,
 neck dissections.
 Hypotensive Anesthesia and Maxillofacial Trauma. The use
of hypotensive anesthesia in trauma patients is relatively
new and controversial.
 A hypotensive approach may limit further bleeding but
could aggravate any existing brain injury.

136.  1) INHALATION SEDATION
 2) I.V SEDATION
 3) GENERAL ANESTHESIA

137.  TECHNIQUES OF ADMINISTRATION-
1)Secure the nasal hood
2)Start the flow of O2 at 6LPM
3)Determine the flow rate for patient
4)Observe the reservoir bag
5)Begin titration of N2O-
6)Observe the patients
7)Continue titration of N2O
8)Observe the patient for ideal sedation phase
9)Begin the dental treatment

138. 10) Observe the patient and inhalation sedation unit
procedure
11) Terminate N2O and give O2 for 3-5 mins.
12) Discharge the patient
13) Record the data.

140.  ZONES OF N2O- four zones of anesthesia have been
described
 1). MODERATE ANALGESIA (6%-25%) 25% is more potent than
10mg of morphine.
 2). DISSOCIATIVE ANALGESIA (26%-45%)- gives psychological
symptoms.
 3). ANALGESIA ANESTHESIA (46%-65%)- complete analgesia
 4). LIGHT ANESTHESIA (66%-80%)- complete analgesia and
amnesia.

141.  The Jorgensen technique is original i.v. moderate sedation
technique. Replaced by BZD or MIDAZ
 I.V USING MIDAZOLAM-
 Rate of injection 1 ml/min--- start with 0.5 min 30 sec
 4-8 mg is sufficient for individual.
 STAGE OF MIDAZOLAM
 STAGE 1 (1-10 min)-good sedation + amneisa
 STAGE 2 (11-30min)- ok sedation +amnesia
 STAGE 3 (31-45 min)- sedation wanes
 STAGE 4( 46-60 min) -clinical recovery

142.  I.V USING DAZEPAM-
 Diazepam is a yellow solution available in 10 ml vial
 Oily viscous causing burning sensation
 Verils sign- over sedation
 dosage 10-12 mg rate 5ml/min. later iv infusion continued
to 1 drop ever 5-10 sec.

143.  STAGE 1(1-5 min)- awareness + good sedation + amnesia
 STAGE 2(6-30 mins)- ↓ awareness+ good sedation +NO
amnesia
 STAGE3(31-45 min)-sedation wanes+ no amnesia
 STAGE4(45-60 min)-anxiolysis+ no amnesia
 STAGE5(> 60 min)- clinical recovery

144. In a nutshell depending upon the duration following can be
done
1)Upto 1hr- diazepam or midaz
2)1-2 hrs diazepam or midaz retitrared
3) >2hrs. Jorgenson technique.
MODIFICATION OF BASIC TECHNIQUE
1)benzodiazepine+ anticholinergic
2)Benzodiazepine + opoid

145. Drugs used in general anesthesia can be divided into following
category
1) i.v induction agents
2) Opoids
3) Neurolept agents
4) Dissociate anesthesia
5) Muscle relaxant
6) Inhalational anesthesia

146.  1) i.v induction agents
1. A)BARBITURATES-
Eg- methohexital, 1mg/kg (>30min)
Thiopental, 150-300 mg (onset-30-40 sec)
ABSOLUTE CONTRAINDICATIONS –
Status asthamatics and porphyria

147.  1.B) BENZODIAZEPINES- provides more slower and gradual
loss of consciouness as compared to barbiturates
 1. C) OTHER AGENTS
Ethomidate –used in children were hypovolemia is required
and hypertension and tachycardia of ketamine are
unacceptable.
Ketamine.
propofol

148.  2) OPOIDS- used for maintainces of G.A. along with N2O and
muscle relaxant.
 Morphine commonly used- 1mg/ml- strong analgesic and
sedation
 Morphine- 10mg/ml- intermediate action
 Fentanyl-short surgical procedure
 Opoid agonist antagonist- eg nalbupine and butorphant.
 Opoid antagonist- naloxone iv. Followed by i.m.

149.  3) NEUROLEPTIC AGENTS
 NEUROALEPTANALGESIA-
 Characterised by- analgesia+ suppression of motor activity+
suppression of autonomic reflex+
CVS stability+ amnesia
Nerolept/ tranqualizer + opioid analgesic
Doperidol fentanyl (0.1mg)
NEUROLEPT ANESTHESIA- N2O+ NEUROLPET ANALGESIA
Used in ASA3 & ASA4

150.  4) DISSOCIATIVE AGENTS
 DISSOCIATIVE ANESTHESIA-
 Produces profound analgesia, and maintains many reflexes
but, may not be protective.
 Used in children and where airway is difficult to maintain.
 DISADVATAGES- ↑ HR
↑ BP
↑ intraocular pressure+ diplopia + nystagmus+ eye
movement.+ hallucination + unpleasant dreams
No antagonist present

151.  5) MUSCLE RELAXANT- mostly neuromuscular blocking drugs
are used .
 Skeletal muscle relaxant.
 Interfere with transmission of impulse from motor nerve to
muscle at the skeletal neuromuscular junction.
 6) INHALATIONAL ANESTHETICS

152.  Reduction of reuptake of calcium ions by sarcoplasmic
reticulum leading to sustained muscle contraction.
 This results in signs of hyper-metabolism like tachycardia,
acidosis, hypercarbia, hypoxemia and hyperthermia
 Discontinue all anesthetic agents.
 Administer Dantrolene 2.5mg/kg IV. And repeat to a total of
10 mg/kg.
 Hyperkalemia to be corrected by Insulin and glucose
 Cold sponging
 Monitor urinary output

153.  CAUSES –
 Swallowing of blood
 Opioid administration
 Hypoxia.
TREATMENT – normally o2 administration and reversal will
decrease the nausea. However if not so then ondansetron 4
mg should be given 10-25 min before the case ends.

154.  INDUCTION
 Initially nitrous oxide 70% in oxygen is used
 Anaesthesia is deepened by the gradual introduction of
increments of a volatile agent e.g sevoflurane.
 Maintenance concentrations of isoflurane (1-2 %)or
sevoflurane(2-3%).
 If spontaneous ventilation is to be maintained through the
procedure, the mask is applied more firmly as consciousness
is lost and airway is supported manually
 Pre- oxygenation may be started with 100% oxygen using
face mask. At the rate of 8L-10L/min

155. AGENT INDUCTION DOSE
Thiopental 3-5 mg/kg
etomidate 0.3mg/kg
Propofol 1.5mg/kg
ketamine 2mg/kg

156.  MAINTAINANCES
 Inhalational agents
 Propofol infusion
 Oxygen + N2O
 Relaxants – VECURONIUM, ATRACURIUM, PANCURONIUM etc.
 Analgesia – opioids
 Sedation – midazolam etc.

157.  REVERSAL
 Check equipment
 Check drugs
 Turn off agents
 Give 100% oxygen
 Suction
 Reverse relaxant
 Usually a combination of neostigmine glycopyrolate in the
ratio of 5:1, or neostigmine and atropine in the ratio of 5:2
is given.
 Wait for adequate breathing
 Wait until patient wakes up
 Extubate and give 100% O 2 by mask

158. ADVANTAGES OF CLOSED BREATHING CIRCIUT.-
 The CO2 absorption is an exothermic reaction and
the system may actively help in maintaining body
temperature.
 Humidity of gases is maintained
 Reduction in atmospheric pollution: Once the expiratory
valve has been closed, no anesthetic escapes, except for
the small percutaneous loss from the patient.

159.  Essential of medical pharmacology 7th edition K.D. Tripathi.
 Textbook of oral and maxillofacial surgery 4th edition. Neelima
Malik.
 Textbook of oral and maxillofacial trauma volume 2 fonseca.
 Mshelia DB, Ogboli-Nwasor EO, Isamade ES. Use of the “L-E-M-O-
N” score in predicting difficult intubation inAfricans. Niger J
Basic Clin Sci 2018;15:17-23
 Guruprasad Y. Preanesthetic dental evaluation for dentofacial
injuries to be managed under general anesthesia. Med J DY Patil
Univ 2016;9:229-30
 James Cphero et al,Adult Airway Evaluation in Oral Surgery,
Anesthesia:Oral and Maxillofacial clinics of North America;
Volume 25, Issue 3, Pages 341-536 (August 2013)

160.  James Cphero et al,Adult Airway Evaluation in Oral Surgery,
Anesthesia:Oral and Maxillofacial clinics of North America;
Volume 25, Issue 3, Pages 341-536 (August 2013)
 Jain K, Gupta N, Yadav M, Thulkar S, Bhatnagar S. Radiological
evaluation of airway – What an anaesthesiologist needs to know!.
Indian J Anaesth 2019;63:257-64.
 Gurudatt CL. The basic anaesthesia machine. Indian J Anaesth
2013;57:438-45.
 Parthasarathy S. The closed circuit and the low flow systems.
Indian J Anaesth 2013;57:516-24

161. THANKYOU