anaesthetics 1 - principles and pharmacology Flashcards

1
Q

General anaesthesia

A

insensibility in whole body, usually causing unconsciousness

cantrally acting drugs - hypnotics, analgesics

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2
Q

Regional anaesthetic

A

insensibility in an area or region of the body

LA applied to nerves supplying relevant area

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3
Q

Local anaesthetic

A

insensibility in relevant part of the body only

LA applied directly to the tissues

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4
Q

How were bleeding, infection and pain in ancient surgery overcome?

A

bleeding - cautery, ligation, pressure, technique
infection - technique, germ theory
pain - herbs, opiates, restraint, alcohol

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5
Q

Early years inhaled therapies

A

ether and nitrous oxide found

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6
Q

How was anaesthesia given in the early years?

A

monotherapy - ether, chloroform

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7
Q

What provided the surgical conditions in early anaesthesia

A

deep planes of anaesthesia

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8
Q

how was ether administered in the early years?

A

schimmelbusch mask

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9
Q

Anaesthetic drugs in the modern era

A

inhaled, IV, muscle relaxants, analgesics, LA

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10
Q

Have the drugs or techniques improved more in anaesthetics?

A

techniques

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11
Q

technique and equipment improvements in the modern era

A
tracheal intubation 
ventilation 
fluid therapy
regional anaesthetic 
monitoring
USS, fibre optics, bis
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12
Q

Functions of modern anaesthetic machine

A

regulation of fresh gases and mixing to deliver precise concentrations
mechanical ventilation, microprocessor controlled

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13
Q

Triad of anaesthesia

A

analgesia
muscle relaxation
hypnosis

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14
Q

Which medications contribute most to each of the triad of anaesthesia?

A

Analgesia - opiates, LA
hypnosis - general anaesthetics
relaxation - muscle relaxants

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15
Q

Idea of balanced anaesthesia

A

different drugs do different jobs -enormous flexibility
titrate doses separately
avoid overdose

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16
Q

Problems with anaesthesia

A

polypharmacy - drug reaction/allergy
muscle relaxation - artificial ventilation and airway
separate relaxation and hypnosis - awareness

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17
Q

How do general anaesthetics work?

A

interfere with chloride ion channels which hyperpolarise and suppress excitatory synaptic activity

18
Q

Explain the difference in how inhaled and IV general anaesthetics work

A

inhaled - dissolve in membrane - direct physical effect

IV - allosteric binding (GABA) open chloride channels

19
Q

Chronology of what is “lost” with general anaesthesia

A

cerebral function lost top down - consciousness first
reflexes spared as small number of synapses
most complex pathways lost first - hearing near end

20
Q

IV anaesthetics onset

A

rapid unconsciousness - 1 arm brain circulation time

21
Q

IV anaesthetics recovery

A

disappear from circulation, redistribution, fat is poorly perfused

22
Q

Inhaled anaesthetics

A

halogenated hydrocarbons - uptake and excretion by lungs

23
Q

inhaled anaesthetics concentration gradient

A

lungs - blood - brain

24
Q

MAC - what is it?

A

measure of potency
low number = high potency
minimum alveolar concentration

25
Q

inhaled anaesthetics induction and waking up

A

slow induction, prolonged by maintenance

stop inhalation and washout to reverse concentration gradient

26
Q

Usual way to induce and maintain general anaesthesia

A

IV - inhalation

27
Q

IV general anaesthetics

A

Propofol

opiate - remifentanil

28
Q

How general anaesthetics affect CVS - brief

A

depress cardiovascular centre
vasodilation and venodilation
negative ionotropic effect - weaken force of contraction

29
Q

How general anaesthetics affect respiratory - brief

A

respiratory depressants and reduce hypoxic/hypercarbic drive
decreased tidial volume and increased rate
VQ mismatch

30
Q

Indications for muscle relaxants

A

ventilation and intubation
body cavity surgery
immobility essential eg neurosurgery

31
Q

Problems with muscle relaxants

A

awareness
incomplete reversal - airway obstruction
apnoea - dependence on airway and ventilatory support

32
Q

Why give intraoperative analgesia

A

prevent arousal
opiates contribute to hypnotic effect
suppress reflex response to pain

33
Q

Positives of regional anaesthesia

A

intense/complete analgesia

no direct hypnotic effect

34
Q

Do local and regional anaesthetic affect resp and CVS function?

A

derange CVS but spare resp

35
Q

Limiting factor of regional anaesthetic

A

toxicity - high absorption levels

36
Q

Toxicity of regional/LA depends on what?

A

dose used
absorption
patient weight
drug

37
Q

Toxicity of LA symptoms and signs

A
circumoral and lingual tingling and numb 
light headed 
coma 
muscular twitching 
coma 
cardiovascular depression 
cardiorespiratory arrest 
tinnitus, vision
38
Q

How do LA display differential blockade?

A

motor fibres spared
pain fibres easily blocked
myelinated thick fibres are relatively spared

39
Q

physiology of neuraxial block - CVS

A

venodilation and vasodilation due to sympathectomy

40
Q

increasing physiological impact - anaesthetics

A
LA
plexus block 
limb block 
neuraxial block 
epidural 
spinal
41
Q

Physiology of neuraxial block - resp

A

expiratory function impaired

decrease FRC and increase VQ mismatch