Anaesthesia

Question 1

Describe the characteristic behaviours of different levels of arousal and sedation

Answer 1

Deep sedation is a depression of consciousness where the patient cannot be aroused

Question 2

What are the 3 main effects of anaesthesia?

Answer 2

Loss of consciousness
Analgesia
Loss of reflexes

Question 3

Outline the Bromage scale in epidural anaesthesia

Answer 3

1 - free movement of legs and feet 0% block
2 - just able to flex knee with free movement of feet (partial, 33% block)
3 - unable to flex knees, but with free movement (almost complete block, 66%)
4 - unable to move legs or feet, complete 100% block

Question 4

What are the classes of agents used for sedation and anaesthesia?

Answer 4

Local anaesthetics (amino esters or amino amides)
General anaesthetics - inhalation or intravenous
Intravenous opioids
Epidural anaesthesia
Neuromuscular blockers

Question 5

What’s the MOA of local anaesthetics and what sensory fibres does it affect best and common side effects?

Answer 5

Weak bases which block Na+ channels to prevent generation and propagation of AP so sensory cortex doesn’t receive pain signals

Work best on smaller, lightly/unmyelinated sensory fibres (Adelta/C)

Side effects: headaches, dizziness, CNS depression

Question 6

What’s the process of general anaesthesia?

Answer 6

Premedication
Induction
Muscle relaxation and intubation
Maintenance
Analgesia
Reversal

Question 7

Outline inhalation anaesthetics

Answer 7

Simple gases and volatile liquids with low-blood solubility for rapid induction
Contain minimum of 25% O2 to prevent hypoxia
Activity linked to blood:gas partition coefficient and oil:gas partition coefficient

Side effects: nephrotoxicity, respiratory depression, respiratory tract irritation, cardiac arrhythmias

Question 8

Outline intravenous anaesthetics

Answer 8

Rapid induction, maintenance by inhalation
Suppress consciousness by increasing inhibitory GABA activity and inhibiting excitatory glutamate activity

General side effects: reduced CNS and sympathetic function, decreased cardiac contractility and respiratory depression

Question 9

What are some drug adjuncts to anaesthesia?

Answer 9

Neuromuscular blockers: block activity at NMJ to relax muscles during surgery

IV opioids: induce analgesia and have sedative effect so can reduce dose of anaesthetic

Question 10

Outline the two classes of NMBs

Answer 10

Depolarising NMB: prolonged depolarisation of ACh receptor prevents further depolarisation and therefore blocks it

Non-depolarising NMB: compete with ACh to bind to receptor and prevent depolarisation once bound, also inhibit presynaptic vesicle release

Question 11

What drugs are used to reverse NMBs?

Answer 11

AChE (Neostigmine) reverse effects of non-depolarising NMB

Sugammadex (selective relaxant binding agent) - selective for rocuronium and vecuronium

Question 12

Define sedation

Answer 12

Allows patients to tolerate unpleasant diagnostic/surgical procedures to relieve anxiety and discomfort
Verbal contact can be maintained

Question 13

What’s conscious sedation? When might it be used?

Answer 13

CNS function is depressed but verbal contact with patient is maintained

During surgery like refixing dislocated shoulder

Question 14

What’s the Ramsay scale and the ideal score on it?

Answer 14

Scale used to assess sedation

2/6 = cooperative, oriented and calm

Question 15

What’s the Richmond agitation sedation scale and the ideal score?

Answer 15

Scale used to measure agitation/sedation of patient

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0 = alert and calm
-5-0 = sedation levels, 0-+4 = agitation levels
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Question 16

What’s the MoA of BDZs, their pros and cons?

Answer 16

GABA PAM (or co-agonists) biding to gamma subunit (Barbiturates bind to beta subunit)

Good sedative, muscle relaxant and anxiolytic
No analgesia and can induce amnesia

Question 17

What are the pros and cons of using opiates as sedatives?

Answer 17

Easy control of pain, good sedative, analgesic and smooth muscle relaxant

Respiratory depression is major side effect

Question 18

What’s the triangle of balanced anaesthesia?

Answer 18

Analgesia
Muscle relaxation
Hypnosis (anaesthesia)

Question 19

In general anaesthetics, what’s the meyer overton theory and MAC?

Answer 19

Correlation between lipid solubility (ability to cross membranes) and minimum alveolar concentration (measure of potency)

Only in inhalation anaesthetics

Question 20

What are adjuncts that can be used in anaesthesia and why?

Answer 20

Antimuscarinics = reduce secretions and bradycardia

Adrenergics = reduce bradycardia, increase resp rate

Antihistamines = reduce gastric secretions and increase pH