7 th semester anesthesia lectures

7/29/2019 7 th semester anesthesia lectures

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Introduction to Anesthesiaand Pain Relief

Department Of Anesthesiology

And Critical CareBPKIHS


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Objectives

define anesthesia and pain relief

mention components of anesthesia

define MAC

mention proposed site of anesthetic action

mention types of anesthetics in clinical use


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Definition Anesthesia- term first used by Greek

philosopher Dioscorides to describe narcotics

like effect- 1st century Defect of sensation- Baileys Dictionary 1721

Privation of Sensation- EncyclopediaBritannica- 1771

Sleep like state that makes possible painlesssurgery- Oliver Wendel Holmes 1846


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Definition contdGeneral or local insensibility to pain and

other sensation, induced by certain drugs

GA-Drug induced reversible depressionof the CNS resulting in the loss ofresponses to and perception of all

external stimuli Balanced anaesthesia

Triad of anesthesia


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Definition contd

Sedation-

Analgesia- Abolition of pain


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History of Anesthesia Date from ancient time

Ether synthesized by V Cordus in 1540, used

by Crawford W Long in 1842, publicized byMorton in 1846

N2O synthesized by Priestley in 1772,experimented by Davy in 1800, used in

anesthesia by Colton and Wells in 1844. Chloroform used as anesthetic by John Snow

in 1853


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History contd ET tube discovered- 1878

LA with cocaine 1885

Thiopentone first used in 1934

Curare first used in anesthesia in 1942Age of Anesthesia started

Halothane synthesized by Suckling in1956


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Molecular Mechanism

Unsolved mystery


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Components of General

Anesthesia

Hypnosis/unconsciousness

Analgesia

Amnesia

Immobility

Attenuation of autonomic response tonoxious stimuli


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How is Anesthesia Measured? Minimum alveolar concentration (MAC)

is the alveolar partial pressure of a gas

at which 50% of humans do notrespond to surgical incision

Limitations

Quantal concept

Not applicable to IVA


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Where In The CNS Do Anesthetic

Act? Spinal cord- inhibition of excitatory

synaptic transmission

Reticular Activating System (RAS)-Locus ceruleus (LC)- Ventrolateralpreoptic nucleus (VLPO)-

Tuberomamillary nucleus (TMN)-sedative actions of GABAergicanesthetics


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Where In The CNS Do Anesthetic

Act? contd Cerebral cortex- depression of the

excitability of the thalamic neurons,

thus blocking thalamo-corticalcommunication potentially resulting inloss of consciousness.


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Interference With The

Electrophysiologic Function Depress neurons subserving

pacemaking (pattern generation)

Decrease neuronal excitability

Inhibiting excitatory synaptictransmission or enhancing inhibitory

synaptic transmission


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Action on the Ion ChannelsVoltage dependent channels

Ligand gated

Glutamate activated

GABA activated channels

Second messenger activated


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Chemical Nature Of Anesthetic

Targets

Meyer- Overton Rule- potencies of

gases as anesthetics strongly correlatedwith their solubility in olive oil

Limitations

Only for volatile agents

Olive oil is poorly characterized


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Chemical Nature Of Anesthetic

Targets

Lipid- membrane perturbation

Membrane expansion Membrane disordering

Lipid phase transition

Protein- hydrophobic sites


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What Is Sedation?

It Is Really A Continuum

Level i minimal sedation

Level ii moderate sedation

Level iii deep sedation

Level iv general anesthesia


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Elements Of Sedation

Responsiveness

Airway

Spontaneous ventilation

Cardiovascular function


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Types Of Anesthetics

General

Regional

Combination

Monitored anesthetic care (MAC)


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General Anesthesia

Spontaneous/controlled ventilation

Endotracheal intubation - ett

Laryngeal mask airway lma

Mask airway


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Regional Anesthesia Field block

Nerve blockPlexus block

EpiduralSubarachnoid


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Nerve Block


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Plexus Block Can use a

catheter for

long termanalgesia


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Epidural Block Can place catheters

at different levels for

differential blocks Can use infusions

with localanesthetics and/or

narcotics


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Spinal Anatomy


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More Spinal Anatomy


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Subarachnoid Block Can use local

anesthetics and/or

narcotics Morphine lasts 12-

24 hours


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Combination

General Regional


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Monitored Anesthetic Care

(MAC)

Pain management

Sedation

Airway management


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Acute Postoperative Pain Relief

Oral Intramuscular Intravenous

Intermittent bolus Continuous infusion Pca patient controlled analgesia

Epidural Intermittent/continuous/pcea Narcotics and/or local anesthetic

Subarachnoid Narcotic

Field block Nerve block

Plexus block/catheter


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Pain Assessment Pain scale

Physical Emotional

Cultural

Age


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Pain Relief Practice Relief of pain adequate for postoperative

rehabilitation

Around the clock medication

Breakthrough pain relief

Narcotics

Non-steroidal anti-inflammatory

Cox 2 receptor inhibitors


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Scope of Anesthesiology

PracticeAnesthesia service

Critical care

Acute and chronic pain management

Resuscitation

Teaching/training Research

Administration


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Objectives define anesthesia and pain relief

mention components of anesthesia

define MAC

mention proposed site of anestheticaction

mention types of anesthetics in clinicaluse


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Thank you

7 th semester anesthesia lectures

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