Surgical anaesthesia

Dr. János Lantos

Department of Surgical Research and Techniques

The revelation

On 16 October 1846 William T.G. Morton performed the first

successful demonstration ofether anaesthesia

in theMassachusetts

General Hospital, Boston, USA.

Early painkilling techniques

The single or combined use of stupefying agents such as

ethyl alcohol, mandragora, cannabis and

opiumto deaden the sensibilities prior to surgery had been practiced

in classical antiquity.

Early painkilling techniquesNon-pharmacological

methods:Blood-letting

(undoubtedly relieved pain, though it was carried out to dangerous and often fatal

excess.)

Cooling with cold water, ice;

Distraction by counterirritation with

stinging nettles;Carotid compression and

nerve clamping.Concussion anaesthesia

relied on the hammer stroke.

Acupuncture

HypnosisCocaine

Закись азота (N2O)

Синтезировал закись азота в 1772 г.

Joseph Priestley(1733-1804)

Веселящие эффекты вдыхания закиси азота впервые были отмечены английским химиком, Хэмфри Дэйви (1800). "

Humphry Davy (1778-1829)

Pioneers in surgical anesthesia

William Thomas Green Morton(1819-1868)

Horace Wells(1815 - 1848)

Charles Jackson(1805 - 1880)

16 October 1846 „Ether Day” in Boston

"Gentlemen, this is not a humbug"

Ether dome c. 1930

Painting of Robert Hinckley

„Ether Dome”

M. H. Hart: The 100A Citadel Press Book, 1978.

1. Mohammed2. Newton3. Jesus Christ4. Buddha5. Confucius6. Saint Paul7. Caj Lun8. Gutenberg9. Columbus10. Einstein.37. Morton.55. Harvey.60. Lister

The ranking of the most influential persons in history

"Gentlemen, this is no humbug"

Queen Victoria(born 1819, reigned 1839 - 1901)

Chloroform (CHCl3)

The delivery in 1853 of Victoria's eighth child

and youngest son, Prince Leopold, was

successful: chloroform was administered by Dr John Snow, the world's

first anaesthetist.

"Dr Snow gave that blessed chloroform and the effect was soothing, quieting and delightful

beyond measure", Her Majesty reported.

Anaesthesia

Anaesthesia can be produced:

- either by administration of drugs which produce a loss of consciousness

(general anaesthesia),

- or localised areas of the body can be made insensitive using local

anaesthetics (local anaesthesia).

Local anaesthesia (analgesia)

Local anaesthetics affect only part of the body:

the loss of sensation in a limited body area,

and the patient remain conscious.

Method:Direct injection of local analgesic drugs close to peripheral nerves, major nerve trunks or nerve

roots to produce analgesia by blocking conduction of afferent impulses.

Local anaesthesia (analgesia)

Degrees of local anaesthesia (analgesia)

Surface anaesthesia: gel, spray

Local infiltration: for minor surgical procedures on skin

Local nerve block:tooth, etc.

Regional anaesthesia:

Spinal anaesthesialocal anaesthetic into CSF below termination of cord at L1

Epidural anaesthesia local anaesthetic agent into the epidural space

General anaesthesia

General surgical anesthesia is defined as a reversible level of unconsciousness

in which the cardiac and pulmonary function remain intact,

the patient does not respond to pain, and muscular relaxation is adequate

for the required operation.

General anaesthesiaGeneral anaesthesia = Hypnosis + Analgesia +

Relaxation

Hypnosis = suppression of consciousnessAnalgesia = suppression of physiological responses to stimuli

Relaxation = suppression of muscle tone and relaxation

A controlled reversible state of:– Amnesia (with loss of consciousness)

– Analgesia– Akinesia (skeletal muscle relaxation)

– Autonomic and sensory reflex blockadeCalled the “4 A’s” of General Anaesthesia.

In practice these effects are produced with a combination of drugs rather than with a single anaesthetic agent.

General anaesthesiaGeneral anaesthesia can be produced:

- either by anaesthetics directly injected into the blood via the intravenous route

(intravenous anaesthesia)- or by anaesthetics absorbed into the

blood alveoli following inhalation(inhalation anaesthesia).

General anaesthetics are given systematically and exert their effect

on the central nervous system.

General anaesthesia

Basis:The various susceptibility of different regions of the central nervous system to anaesthetic

agents.

cerebral cortexsubcortical motor centers

midbraincerebellum

medulla oblongata

This selective susceptibility allows the induction of narcosis without the serious risk of circulatory and

pulmonary failure.

The signs of depth of anaesthesia

Circulation: blood pressure, heart rate

Respiration: frequency, volume, character (thorax, diaphragm)

Eye: motion, pupil size

reflexes: light, eye closing, conjunctiva, cornea

Other reflexes:coughing, swallowing, vomiting

Muscle tone:limb, abdomen, smooth muscle

Stages of anaesthesia

Arthur E. Guedel1883-1956

Stages of Anesthesia Stage of Analgesia:

Analgesia without amnesia, impaired judgment, vertigo/ataxia, increased respiration, blood pressure, heart

rate

Stage of Excitement:Delirious, excited, amnesic. 

Irregular respiration, struggling, retching and vomiting

Stage of Surgical AnesthesiaRecurrence of regular respiration --> cessation,

Loss of corneal, swallowing, eyelid reflexesSkeletal muscle relaxationDecreased blood pressure

Stage of Medullary DepressionBegins at cessation of spontaneous respiration

--> severe depression of vasomotor and respiratory centers-->without support = Death

Стадии эфирного наркоза

Stages

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Tolerance

Excitation

Analgesia

Asfixia

Risk of overdosageIndividual variation of patients’ response to

general anaesthetics are so great that reliable dose/response relationship do not

exist. General anaesthetics can not be administered

in a predetermined dosage based on mg/kg body weight without running the risk of

serious overdosage in some patients and inadequate depth of anaesthesia in others.

Evaluation of depth of anaesthesia is neither easy nor precise but instead highly subjective,

clinical signs varying not only with each general anaesthetic but also with each

patient.

Monitoring during anaesthesia

General anaesthesia removes ability of patient to protect himself. Safety and physiological control becomes the

responsibility of the anaesthetist, therefore the continuous presence of an adequately trained

anaesthetist is essential, and accurate monitoring of vital signs is obligatory.

Anaesthetist needs to: maintain airway and oxygenation, preserve circulation, prevent

hypothermia, prevent injury, monitor during anaesthesia

Monitoring of the following is essential for all patients: temperature, heart rate, blood pressure, ECG, oxygen content

of inspiratory gas mix, end-tidal carbon dioxide, pulse oximetry

Facilities for cardiopulmonary resuscitation should be immediately available.

Inhalation anaesthetics

Anaesthesia is normally maintained with inhaled volatile anaesthetic agents.

- Drugs administered via face mask or endotracheal tube.

- Volatile liquids vaporized in a carrier gas.- Nitrous Oxide (N2O), a gas at ambient temperature

/pressure, is a low potency adjunct.

Potency of inhalation anaesthetics can be characterised by

MAC = Minimum alveolar concentrationIt is the alveolar concentration required to keep 50% of population unresponsive to a

painful stimuli.

Characteristics of inhalation anaesthetics

Enflurane Desflurane

Sevoflurane

Halothane Isoflurane

They are lipid soluble hydrocarbons.They have high saturated vapour pressures.

Modern agents are potent, non-inflammable and non-explosive.

Properties of inhalation anaesthetics

Nitrous oxide

Halothan

Enfluran

Isofluran Sevofluran Desfluran

Induction fast medium medium medium fast fast

Recovery fast medium medium medium fast fast

Analgesic effect + -

-

-

-

-

Respiratory track irritation

- -

- -

- +

Blood pressure

- decreases

decreases

decreases

decreases decreases

Metabolism 0 % 20 % 2,4 % 0,2 % 3 % 0,02 %

MAC 104 % 0,75 % 1,6 % 1,2 % 2,05 % 6 %

Induction dose

3 % 1-10 % 1-4 % 5-8 % 4-11 %

Maintaining dose

2,05 % 0,6-3 % 0,5-3 % 0,5-3 % 2-6 %

The advantages and disadvantages

Inhalation anaesthesia

Intravenous anaesthesia

Advantages - controllable reversibility

(duration of action can be controlled)

- fast induction

Disadvantages

- relatively slow induction

- irritation of airways- claustrophobic feeling

- duration of action can not be controlled

(termination of action require biotransformation or

excretion processes over which the anesthetist has no

control)

Properties of intravenous anaesthetics

Drug Induction

Recovery

Main unwanted

effects

Notes

Thiopentone(barbiturate)

fast accumu-lation occurs giving slow

recovery

Cardiovas-cular and

respiratory depression

Widely used agent for routine purposes

Midazolam(benzodiazepine)

slow slower than

others

Little cardiovascular and

respiratory depression

Ketamine slow Psychoto-mimetic effect

Produces good analgesia and

amnesia

Propofol fast very fast Cardiovas-cular and

respiratory deprivation

Rapidly metabolized.

Possible to use as continuous

infusion

Muscle relaxants

Muscle relaxants are either depolarising or non-depolarising agents

Depolarising agentsFor example - suxamethonium

Act rapidly within seconds and last for approximately 5 minutesUsed during induction of anaesthesia

Non-depolarising agentsFor example - vecuronium

Act over 2-3 minutes and effects last for 30 minutes to one hourCompetitive antagonism of acetylcholine receptor

Used for muscle relaxation

Premedication

Is the administration of drugs prior to an anaesthetic.

Has three potentially useful effects: Anxiolysis

Can be achieved with benzodiazepines.

Reduce parasympathetic reflexes parasympatholytic drugs (Atropine)

AnalgesiaBest achieved with strong opiates (Fentanyl).

Opiate analgesics also have useful sedative properties.

Advantage: decreased requirement for general anaesthetic

agents

Systems in inhalation anaesthesia

1. Open system: no reservoir, no rebreathing, no provision for assisting ventilation: simple, cheap, but difficult to maintain a stable anaesthetic state. Pollutes the environment.

2. Semi open system: with a gas reservoir and no rebreathing: commonly used in paediatric anaesthesia. Stable system and allows assisted and controlled ventilation.

3. Semi closed system (most commonly used): incorporates a gas reservoir and rebreating circuit that allows partial rebreathing:

- soda lime container; - provides an inherent stability.

4. Closed system: has a gas reservoir but no gas escapes from the system:

- difficult to control; - economical, minimally pollutes the environment.

Современные аппараты для наркоза

В 70’х… …и сейчас

Scheme of anaesthetic circuit

Gas supply

Rebreathing circuit

Pop-off valve

Sources

www.virtual-anaesthesia-textbook.com/www.general-anaesthesia.com/

www.johnpowell.net/

N. M. Green: AnesthesiaJ. J. Savarese, E. Lowenstein: Anesthesia