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GENERAL ANAESTHESIA
Presented by
Dr. Vishal DewalwarLecturer
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Definition
A controlled state of unconsciousness
in which there is a loss of protective
reflexes, including the ability to
maintain an airway independently and
to respond appropriately to physicalstimulation. or verbal command.
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Surgery Before Anesthesia
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Fun and Frolic led to early Anaesthesia
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History of Anaesthesia
Joseph Priestlydiscovered N2O in 1773
Sir Humphrey Davyexperimented with
N2O, reported loss of pain, euphoria
Horace Wells in 1844 demonstrated N2O
for tooth extraction
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William Morton, dentistfirst
demonstration of successful surgical
anesthesia with ether in 1846
Dr. John Snow administered chloroform to
Queen Victoria (1853)popularized
anesthesia for childbirth in UK
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Goals of Anaesthesia
Hypnosis (unconsciousness)
Amnesia
Analgesia Immobility/decreased muscle tone
(relaxation of skeletal muscle)
Inhibition of nociceptive reflexes Reduction of certain autonomic reflexes
(gag reflex, tachycardia, vasoconstriction)
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Preanaesthetic evaluation
The main purpose of preoperative visit is to
assess the patients fitness for anaesthesia.
This visit allows the most suitable
anaesthetic technique to be determined, any
potential interaction between concurrentdiseases, drugs and anaesthesia to be
anticipated and also provides reassurance to
the patient.
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Anaesthetic History
Previous anaesthesia and major surgeries
Past and present medical history
- CVS, RS
- Pregnancy
Drug and allergies Personal history
- HabitsSmoking, Alcohol, Drugs
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Physical Examination
Cardiovascular System
- Cardiac arrhythmias
- Blood pressure
- Peripheral veins
Respiratory System
- Asthma
- COPD`s
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Nervous system
- motor or sensory impairment
Musculoskeletal system
- TMJ- Cervical spondilitis
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Airway
- assessment is made in 3 stages
1. Observation of patients anatomy
2. Bedside tests
3. X- rays
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1. Observation of patients anatomy- Trismus
- Retrognathia
- Position, no. and health of teeth- Size of tongue
- Deviated larynx or trachea
- Midline or lateral swelling of neck
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2. Bedside tests
a. Mallampati`s criteria
- view of pharyngeal
structures is noted
and graded as I-IV
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b. Thyromeatal distance
- distance between
bony point of the chin
and the prominence ofthyroid cartilage
- a distance less than
7cm suggests difficult
intubation
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3. X - rays
- Lateral and AP neck X - rays are advised
- measurements can be made on lateral
X - ray of head and neck
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Preanaesthetic medication
It refers to the drugs administered to facilitate theinduction and maintenance of anaesthesia.
The 6 A`s premedication1.Anxiolysis
2.Amnesia
3.Anti-emetic
4.Antacid
5.Anti-autonomic
6.Analgesic
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Aims
1. Relief of anxiety and apprehension
preoperatively and to facilitate smooth
induction.
2. Amnesia for pre and post operative events.
3. Supplement analgesic action of
anaesthetics and potentiate them so thatless anaesthetic is needed.
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3. Decrease secretions and vagal stimulationcaused by anaesthetics.
4. Antiemetic effect extending to the
postoperative period.
5. Decreases acidity and volume of gastric
acid so that it is less damage if aspirated.
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Anticholinergics
ATROPINE
Atropine is the prototype drug of anticholinergic class and is
highly selective for muscarinic receptors.
ACTION:-Blocks the muscarinic effects of acetylcholine as it has
the same affinity for muscarinic receptors as
acetylcholine but poor intrinsic activity.
USES :- 1. Preanasesthetic medication
2.Organophosphorous poisoning
3.Bradyarrhythmias
4.Motion sickness
5.Colic and dysmenorrehea
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SIDE EFECTS :-1.Dry mouth, dysphagia, constipation, paralytic ileus
2.Urinary retention
3.Blurred vision and precipitates of glaucoma
4.Allergic dermatitis
PRECAUTIONS:-1.In elderly it precipitates glaucoma and urinary
retention(if enlarged prostate).
2.In chronic lung diseases it dries up secretions.
DOSE :-ATROPINE SULPHATE 0.6mg/ml inj. i.m.,i.v.
6.Peptic ulcer
7.Parkinson`s disease
8.To produce mydriasis and cycloplegia
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RANITIDINE
It is introduced as a non-imidazole H2 blocker.
ACTION:-1. Abolishes histamine stimulated gastric acid secretion
and flushing.
2. Inhibits gastric H2 receptors, this reduces basal, 24 hours
and nocturnal acid secretion.
3. Has mucosal protective action.
USES:- 1.Preaneasthetic medication.
2.Peptic ulcer.
3.Esophagitis.
H2 BLOCKER
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6.Gastro oesophageal reflux disease(GERD).
SIDE EFFECTS :- 1.Blood dycrasias.
2.Skin rash.
3.Leucopenia
DOSE :-300mg/day or 150mg BD
50mg i.m. or slow i.v.every 6 to 8 hrs.
TRADE NAME :- ULTEC,ZENTAC,RANITINE,ACILOC.
4.Stress ulcer
5.Zollinger- Ellision syndrome
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ONDANSETRON
It is the prototype of a new class of anti emetic drugs developed tocontrol cancer chemotherapy/radiotherapy induced vomitting and later
found to be highly effective in postoperative nausea and vomiting as
well.
USES:- 1.Preaneasthetic medication.
2.It is given before starting chemotherapy
especially CISPLASTIN.
SIDE EFFECTS:- 1.GI:diarrohea
.
ANTIEMETIC
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DOSE : 4-8mg BD or TDS orally or i.v.
TRADE NAME:-EMESET,VOMIZ,OSETRON
2.Skin:rashes
3.Miscellaneous;headache, blurred vision,
hypokalemia, anaphylactoid reaction.
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INTRAVENOUS ANAESTHETICS
INTRAVENOUS
Inducing agents Slower acting drugs
Thiopentone sodium Benzodiazepines
Propofol Diazepam
Midazolam
Dissociative anaesthesia
Ketamine
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Inducing agents
These are drugs which on i.v. injection
produce loss of consciousness.
They are generally used for induction
because of rapidity of onset of action.
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THIOPENTONE SODIUM
It is an ultra short acting barbiturate highly soluble in water.
It must be prepared freshly before injection.
ACTION :- Its undissociated form has high lipid solubility & enters
brain almost instantaneously to produce unconsciousness
in 15-20 sec & last till 10-20 min.
USES :- 1.Inducing agent along with anaesthetic.
2. Rapid control of convulsions.
3. Gradual i.v. infusion of subanaesthetic doses can be
used to facilitate verbal communication with psychiatric
patient.
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ADVERSE EFFECTS:- 1. Laryngosparm when respiratory secretions
or other irritants are present.
2. Shivering & delirium.3. Post operative pain.
CONTRAINDICATION:- Acute intermittent porphyria.
N.B. :- Succinylcholine & thiopentone react
chemically should not be mixed in the
same syringe.
DOSE :- 3-5 mg/kg as a 2.5% solution.
TRADE NAME :- PENTOTHAL, INTRAVAL SODIUM.
PROPOFOL
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PROPOFOL
It is an oily liquid introduced recently as a 1% emulsion for i.v.
induction & short duration anaesthesia.
ACTION :- Unconsciousness after propofol injection occurs in
15-45sec & lasts for 15min.
USES :- 1.Inducing agent; particularly for out patient
surgery.
2. In subaneasthetic doses; used for sedation in
intensive care units.
SIDE EFFECTS :- 1. Pain during injection.
2. Dose dependent respiratory depression.
DOSE :- 2mg/kg bolus i.v. for induction
9mg/kg/hr for maintenance.
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SLOWER ACTING DRUGS
BENZODIAZEPINES
In addition to preanaesthetic medication; BZDs are now frequentlyused for inducing, maintaining and supplementing anaesthesia.
ACTION :-Injected i.v. produce sedation, amnesia and thenunconsciousness in 10-15 minutes. If no other
anaesthetic or opioid is given, the patient becomes
responsive in 1 hr but amnesia persists for 2-3 hr
and sedation for 6 hr or more.
USES :-1. Sedative and Hypnotic.
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2. Muscle Relaxant
3. Preanaesthetic Medication
4. Alcohol Withdrawal
5. Anxiety Neurosis
6. Petit-mal, Psychomotor and Status Epilepticus.SIDE EFFECTS:- 1. Drowsiness
2. Ataxia
3. Respiratory Depression4. Hypotension
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MIDAZOLAM
Water Soluble
Non IrritatingFaster and Shorter Acting
3 Times more potent than Diazepam
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KETAMINE
It induces a so called Dissociative Anaesthesia
- profound analgesia,immobility, amnesia with light sleep and feeling of dissociation from
ones own body and the surroundings.
ACTION:- It acts within a minute and recovery starts after 10-15
minutes, but patient remains amnesic for 1-2 hrs.
USES :-1.Recommended for Operations on head and neck.
2.In patients who have bled.
3.In Asthmatics (relieves bronchopasm).
4.In burn dressings.
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SIDE EFFECTS :- 1. Emergence Delirium
2. Hallucinations
3. Involuntary Movements
DOSE :- 1-4(average 2)mg/kg i.v. or
6.5-13(average10)mg/kg i.m.
TRADE NAME :- KETAMIN, KETLAR.
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SKELETAL MUSCLE RELAXANTS
Skeletal muscle relaxants are drugs that act peripherally at the neuro
muscular junction/muscle fibre itself or centrally in the cerebrospinal
axis to reduce muscle tone and/or cause paralysis.
Peripherally acting Centrally acting
muscle relaxants muscle relaxants
*Non Depolarizing blockers *Mephenesin group
Pancuronium Chlorzoxazone
d-Tubocurarine *Benzodiazepines
*Depolarizing blockers Diazepam and others
Succinylcholine *GABA Derivative
Baclofen
Comparative features of central and peripheral muscle relaxants:-
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Comparative features of central and peripheral muscle relaxants:
Centrally acting Peripherally acting
1.Decrease muscle tone without 1.Cause muscle paralysis,
reducing voluntary action. Voluntary movements lost.
2.Selectively inhibit polysynaptic 2.Block neuromuscular
reflexes in CNS. transmission.
3.Cause CNS depression. 3.No effect on CNS.
4.Given orally sometimes 4.Practically always given
parenterally. i.v.
5.Used in chronic spastic condition, 5.Used for short term purposes
acute muscle spasms,tetanus. (surgical procedures).
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MECHAISM OF ACTION
NON-DEPOLARIZING BLOCKERS(COMPETITIVE)-
They combine with the receptors on the motor end-plate and thus
block the action of acetylcholine by competitive blockade.
DEPOLARIZING BLOCKERS(NON-COMPETITIVE)-
Depolarize muscle end-plates by opening Na-channels & thus act as
partial agonist of acetylcholine.
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SUCCINYLCHOLINE
Commonly used muscle relaxant for passing tracheal tube.
Induces rapid, complete and predictable paralysis with
spontaneous recovery in 5min.
DOSE :- 50mg/ml injection, 2ml ampule.
TRADE NAME:- MIDARINE.
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PANCURONIUM
Synthetic steroidal compound.
Provides good cardiovascular stability.
Seldom induces flushing, bronchospasm or cardiac arrhythmias.
Relatively inexpensive.
Reversal often required due to its long duration of action.
DOSE :- 2mg/ml in 2ml amp.
TRADE NAME:- PAVULON, PANCONIUM.
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ATRACURIUM
4 times less potent than pancuronium & shorter acting.
Inactivation in plasma by spontaneous non-enzymatic degradation
(HOFFMANN ELIMINATION).
DOSE :- 10mg/ml injection in 2.5ml vial.
TRADE NAME:- TRACRIUM.
ANALGESICS
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ANALGESICS
DICLOFENAC SODIUM
It is non-opioid analgesic , anti-pyeretic non-steroidal
anti-inflammatory drug.
ACTION :- It inhibits synthesis and has short lasting
antiplatelet action.
USES :-1. Post-traumatic and postoperative
inflammatory conditions-affords quick relief ofpain and edema.
2. Rheumatoid & osteoarthritis, bursitis.
3. Ankylosing spondylitis.
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SIDE EFFECTS :-1.Epigastric pain, nausea.
2.Headache, dizziness,rashes.
DOSE :- 50 mg TDS
75 mg deep i.m.
TRADE NAME :- VOVERAN, DICLONAC.
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PENTAZOCINE
It is the first opioid agonistantagonist to be used as an analgesic.
ACTION :- 1. Raises pain threshold & modifies
emotional reaction to pain.
2.Inhibits transmission of impulses across
the pain pathways in CNS.
USES :-1. Potent analgesic with low addiction
liability.
SIDE EFFECTS :- 1. Respiratory depression.
2. Hallucinations and unpleasant dreams.
3. Pulmonary & systemic hypertension.
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DOSE :- 50-100 mg orally.
30-60 mg i.m. , s.c.
TRADE NAME :- FORTWIN, MERIWYN, SOSEGON.
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THANK YOU