1 - Principles of Pharmacology

Question 1

Define general anaesthesia?

Answer 1

produces insensibility in the whole body, usually causing unconsciousness

Question 2

which type of drugs can be used as general anaesthetics?

Answer 2

centrally acting drugs - hypnotics, analgesics etc.

Question 3

define regional anaesthesia?

Answer 3

producing insensibility in an area or region of the body -

Local anaesthetics applied to nerves supplying relevant area

Question 4

define local anaesthetics?

Answer 4

producing insensibility in only the relevant part of the body - applied directly to the tissues

Question 5

describe what is meant by monotherapy?

Answer 5

when anaesthesia used to be delivered using high concentrations of single agents in spontaneously breathing patients

Question 6

in which ways were monotherapies used?

Answer 6

chloroforms

ethers

Question 7

what are the risks associated with monotherapy?

Answer 7

cardiac depression

respiratory depression

Question 8

In terms of development, where is the area of major progress?

Answer 8

in techniques and equipment, rather than the drugs themselves

Question 9

give an example of monitoring which has become far more accessible and affordable?

Answer 9

pulse oximetry

Question 10

describe 4 functions of the modern anaesthetic machine?

Answer 10

• Regulation of fresh gases and mixing to deliver precise concentrations of gaseous agents
• Addition of precise concentrations of inhaled anaesthetic gases
• CO2 removal to allow recirculation of inhaled gases
• Mechanical ventilation

Question 11

what system is used to determine safety of patient and risk of mortality?

Answer 11

ASA system

Question 12

in ASA system, in which groups is mortality concentrated?

Answer 12

groups 3-5

Question 13

describe ASA 1 patient?

Answer 13

normal, fit, healthy patient

Question 14

describe ASA 2 patient?

Answer 14

patient with mild systemic disease

Question 15

describe ASA 3 patient?

Answer 15

patient with severe systemic disease

Question 16

describe ASA 4 patient?

Answer 16

patient with severe systemic disease that is constant threat to life

Question 17

describe ASA 5 patient?

Answer 17

moribund patient, not expected to survive - surgery is carried out in desperation

Question 18

describe ASA 6 patient?

Answer 18

patient declared brain dead - usually undergoing organ retrieval

Question 19

what is the triad of anaesthetics?

Answer 19

hypnosis - unconsciousness

analgesia - pain relief

relaxation - skeletal muscle relaxation

Question 20

what are 2 benefits of balanced anaesthetics - i.e. having different drugs doing different jobs?

Answer 20

allows a great degree of control over the individual components of the triad

Helps keep doses of individual drugs down

Question 21

describe 3 potential problems with balanced anaesthetics?

Answer 21

polypharmacy

muscle relaxation

separation of relaxation and hypnosis - awareness

Question 22

what do general anaesthetics provide?

Answer 22

unconsciousness and muscle relaxation

Question 23

what separates GAs from sedatives?

Answer 23

the potency

Question 24

how do GA agents act?

Answer 24

they interfere with neuronal ion channels + hyperpolarise neurones - this means they are less likely to ‘fire’ and suppresses excitatory synaptic activity

Question 25

how do inhalation GA agents work?

Answer 25

dissolve in membranes and provide a direct physical effect

Question 26

how do IV GA agents work?

Answer 26

bind allosterically to GABA receptors - this opens the Cl-channels

Question 27

association with GA and cerebral function?

Answer 27

"lost from top down" - most complex processes are interrupted first

Question 28

why is order of cerebral function under GAs fortunate?

Answer 28

it allows unconsciousness to be achieved while some automatic and autonomic functions are preserved such as respiration and blood pressure homeostasis

Question 29

in terms of time, are IV anaesthetics quick to work and why?

Answer 29

yes - because they cross the blood brain barrier rapidly and get into the neural tissues v quickly

Question 30

How are IV drugs able to cross the blood brain barrier?

Answer 30

they are highly fat-soluble drugs

Question 31

Do IV drugs stay in the blood for a long time?

Answer 31

no - the drug moves to other parts of the body before being metabolised

Question 32

what are inhalational anaesthetics AKA?

Answer 32

halogenated hydrocarbons

Question 33

how are inhalational anaesthetics almost exclusively taken up and excreted?

Answer 33

via the lungs

Question 34

how does the inhalational anaesthetic correspond to the pressure gradient?

Answer 34

it moves down the pressure gradient from lungs, to blood, to brain - causing unconsciousness

Question 35

define MAC?

Answer 35

minimum alveolar concentration of a drug which is required to produce anaesthesia

Question 36

what is MAC?

Answer 36

measure of potency - low number = high potency

Question 37

describe the induction of Inhalational Anaesthetics?

Answer 37

slow

Question 38

describe the maintenance of anaesthesia in Inhalational Anaesthetics?

Answer 38

prolong duration - very flexible drugs

Question 39

what is the most common sequence of general anaesthesia?

Answer 39

IV induction followed by inhalational maintenance

Question 40

describe 3 central effects of GAs on depressing the CVS centre?

Answer 40

reduce sympathetic outflow negative inotropic/chronotropic effect on heart reduced vasoconstrictor tone → vasodilation

Question 41

describe 3 direct effects of GAs on CVS?

Answer 41

negatively inotropic vasodilation → decreased peripheral resistance venodilation: - decreased venous return, - decreased cardiac output

Question 42

effect of GAs on resp and CVS?

Answer 42

CVS and respiratory depressants

Question 43

4 effects which demonstrate GAs as respiratory depressants?

Answer 43

Reduce hypoxic and hypercarbic drive Decreased tidal volume & increase rate Paralyse cilia Decrease FRC

Question 44

what do muscle relaxants do?

Answer 44

they paralyse ('relax') skeletal muscle

Question 45

which other component of the triad compliments the use of muscle relaxants?

Answer 45

unconsciousness

Question 46

give 4 indications for muscle relaxants?

Answer 46

ventilation & Intubation microscopic surgery neurosurgery body cavity surgery (access)

Question 47

what is the biggest fear when using muscle relaxants?

Answer 47

awareness

Question 48

2 potential other issues using muscle relaxants?

Answer 48

airway obstruction/ respiratory insufficiency need to maintain and protect the airway and provide ventilation of the lungs - if not = death

Question 49

with which other part of the triad is analgesia usually paired with (but not always)?

Answer 49

unconsciousness

Question 50

give 3 reasons for using intraoperative analgesia?

Answer 50

Prevention of arousal Opiates contribute to hypnotic effect of GA Suppression of reflex responses to painful stimuli

Question 51

give an example of an opiate used intraoperatively?

Answer 51

fentanyl

Question 52

name 2 opiates used intro and post-operatively?

Answer 52

morphine oxycodone

Question 53

describe the action of remifentanil?

Answer 53

very highly potent and extremely short acting - therefore used as adjunct to inhalation/ IV agents but offers no post-op analgesia

Question 54

name 3 local anaesthetics?

Answer 54

lignocaine bupivacaine ropivacaine

Question 55

how do local anaesthetics work?

Answer 55

by blocking Na+ channels and preventing axonal action potential from propagating

Question 56

in which way are local anaesthetics NOT delivered?

Answer 56

IV

Question 57

benefit of delivering analgesia with local techniques?

Answer 57

avoidance of reliance on opioid analgesics

Question 58

what is a safe and conservative way to deliver local anaesthetic?

Answer 58

via US - ultrasound guided regional anaesthesia

Question 59

what is the main factor limiting use of local anaesthetic?

Answer 59

toxicity

Question 60

4 factors which toxicity depends on?

Answer 60

dose used rate of absorption (site dependant) patient weight drug

Question 61

name 4 signs of local anaesthetic toxicity?

Answer 61

Light-headedness Tinnitus, visual disturbances Muscular twitching Drowsiness

Question 62

describe the differential blockade of local anaesthetic?

Answer 62

motor fibres (due to high degree of myelination) are relatively spared - pain fibres are easily blocked (due to being thinner)

Question 63

MAP equation?

Answer 63

MAP = CO x SVR ``` CO = venodilation SVR = arteriolar vasodilation ```

Question 64

in terms of neuraxial block, where is local anaesthetic injected into in spinal/ subarachnoid block?

Answer 64

CSF surrounding the cord +/- spinal roots

Question 65

how is epidural anaesthesia formed?

Answer 65

injection of local anaesthetic into the epidural space (fat layer)

Question 66

distinguish between local anaesthetic in subarachnoid space and epidural space?

Answer 66

subarachnoid - nerves are made up of neural tissue only - therefore LA penetrates easily and so low doses of LA are needed epidural - nerves have thick fibrous layer, therefore difficult to penetrate - therefore much higher doses

Question 67

risk associated with LA in epidural space?

Answer 67

massive overdose if injected into subarachnoid space