anaesthetics intro

Question 1

general anaesthesia

Answer 1

produces insensibility in whole body, usually causing unconsciousness

centrally acting drugs

Question 2

regional anaesthesia

Answer 2

producing insensibility in an area/region of body
local anaesthetics applied to nerves supplying relevant area

anaesthetic agent applied to nerve and anaesthesia produced in distal site served by that nerve

Question 3

local anaesthesia

Answer 3

insensibility only in relevant part of body
local anaesthetics applied directly to tissues

unlike regional anaesthesia, anaesthesia produced at site of injection

Question 4

regional analgesia vs anaesthesia

Answer 4

regional anaesthesia patient should have little or no sensation of any sort from blocked area: warmth, proprioception, light touch, vibration, pain

regional analgesia only pain sensation needs to be removed/reduced. Other sensation may be retained to varying extents

Question 5

different categories of anaesthetic drugs

Answer 5

inhalational anaesthetics
intravenous anaesthetics
muscle relaxants
local anaesthetics
analgesics

Question 6

different techniques and equipment

Answer 6

tracheal intubation 
ventilation 
fluid therapy 
regional anaesthesia 
monitoring

Question 7

functions of modern anaesthetic machine

Answer 7

• deliver precise concentrations of gaseous agents
• addition of precise concentrations oh inhaled anaesthetic gases
• co2 removal to allow recirculation of inhale gases
• mechanical ventilation
• most monitoring

Question 8

ASA system

Answer 8

mortality concentrated in ASA groups 3-5

fit healthy patients are at very little risk indeed

Question 9

ASA 1

Answer 9

normal, fit, healthy patient

Question 10

ASA 2

Answer 10

patient with mild systemic disease

Question 11

ASA 3

Answer 11

patient with severe systemic disease

Question 12

ASA 4

Answer 12

patient with severe systemic disease that is a constant threat to life

Question 13

ASA 5

Answer 13

moribund patient, not expected to survive

surgery carried out in desperation

Question 14

ASA 6

Answer 14

patient declared brain dead, usually undergoing organ retrieval

Question 15

triad of anaesthesia

Answer 15

hypnosis
analgesia
relaxation

Question 16

triad of anaesthesia: hypnosis

Answer 16

unconsciousness

necessary component of any general anaesthetics

Question 17

triad of anaesthesia: analgesia

Answer 17

pain relief, removal of perception of unpleasant stimulus

if pt unconscious and so unaware of pain, analgesia usually required to suppress reflex autonomic responses to painful stimuli

Question 18

triad of anaesthesia: relaxation

Answer 18

refers to skeletal muscle relaxation necessary to provide immobility for certain procedures
allow access to body cavities and to permit artificial ventilation

Question 19

balanced anaesthesia

Answer 19

use different drugs to do different jobs
titrate doses separately + so more accurately to requirements
avoid over-dosage
enormous flexibility

Question 20

problems with balanced anaesthesia

Answer 20

polypharmacy - increasing chance of drug reactions/allergies

muscle relaxation

separation of relaxation and hyponosis –> awareness: possible to have patient paralysed with muscle relaxant yet insufficiently anaesthetised so aware

Question 21

general anaesthetic agents

Answer 21

provide unconsciousness as well as a small degree of muscle reactions
they may also provide some analgesia, but for all except ketamine, analgesia is negligible

Question 22

how to general anaesthetic agents work

Answer 22

• interfere with neuronal ion channels
• hyper-polarise neurones = less likely to fire

suppress neuronal activity

inhalational agents dissolve in membranes - direct physical effect

IV agents - allosteric binding: GABA receptors - open chloride channels

Question 23

IV anaesthetics

Answer 23

rapid onset of unconsciousness

rapid recovery

Question 24

target controlled infusion pump system

Answer 24

allows very accurate infusion to achieve specific blood or brain concentrations of agents

Question 25

inhalational anaesthetics

Answer 25

halogenated hydrocarbons

uptake and excretion in lungs - partial pressure gradient

Question 26

inhalational anaesthetics: minimum alveolar concentration

Answer 26

measure of potency

low number = high potency

concept of the concentration of drug required in the alveoli which is required to produce anaethesia

Question 27

main role of inhalational agents

Answer 27

extension or continuation of anaesthesia

Question 28

sequence of general anaesthesia

Answer 28

IV induction followed by inhalational maintenance

more modern agents with more sophisticated infusion techniques allow use of IV maintenance

Question 29

physiology of GA: CVS

Answer 29

reduce sympathetic outflow
negative iontropic/chronotropic effect on heart
reduced vasoconstrictor tone –> vasodilatoin

decreased peripheral resistance, venous return and cardiac output.

Question 30

physiology of GA: repsiratory

Answer 30

reduce hypoxic and hypercarbic drive
decreased tidal volume+ inc rate 
paralyse cilia 
decrease functional residual capacity 
-lower lung volumes
-VQ mismatch

Question 31

indications for muscle relaxants

Answer 31

ventilation + intubation
when immobolity is essential e.g. microscopic surgery, neurosurgery
body cavity surgery (access_

Question 32

how do muscle relaxants work

Answer 32

work on NMJ in skeletal muscle

do not effect cardiac or smooth muscle

Question 33

problems with muscle relaxants

Answer 33

awareness: separation of unconsciousness from hypnosis in triad

incomplete reversal: may lead to airway obstruction

apnoea: dependence on airway and ventilatory support

Question 34

intraoperative analgesia

Answer 34

prevention of arousal - pain wakes you up

opiates contribute to hypnotic effect of GA

suppression of reflex response to painful stimuli e.g. tachycardia

Question 35

regional anaesthesia

Answer 35

intense/complete analgesia

no direct hypnotic effects

can allow lighter levels of GA to be used by eliminating painful surgical stimuli

Question 36

local analgesia

Answer 36

analgesia with no hypnosis, little bit of muscle relaxation too

work by blocking Na+ channels and preventing axonal AP from propagating

pharmacologically filthy with effects on every tissue so is toxic if delivered wrongly