Anaesthetics

Question 1

Describe the different classifications of anaesthetic. (5)

Answer 1

General (inhalation or intravenous) or local (regional).

Question 2

Describe the concept of conscious sedation. (4)

Answer 2

Small amounts of anaesthetic or benzodiazepines used to produce a “sleepy” state - maintain verbal contact but feel comfortable. Used frequently in dentistry.

Question 3

Describe the process of administering anaesthetics in practice. (8)

Answer 3

1 - premedication - hypnotic like benzodiazepine.
2 - induction - usually IV but can be inhalational.
3 - interoperative analgesia - usually an opioid.
4 - muscle paralysis - facilitates intubation / ventilation / stillness.
5 - maintenence - IV pump or inhalational
6 - surgery
7 - reversal of muscle paralysis and post operative analgesia
8 - provision for PONV.

Question 4

Describe examples of volatile general anaesthetics. (3)

Answer 4

N20 - anaesthetic and analgesic
Xenon - neuroprotective so good in children.
Most contain Cl or F.

Question 5

Name 4 examples of intravenous anaesthetics. (4)

Answer 5

Propafol
Barbiturates
Etomidate
Ketamine

Question 6

Describe stage 1 of Guedel’s Signs. (5)

Answer 6

Analgesia - conscious, muscle tone normal, eye movements slight, breaking deep and regular.

Question 7

Describe stage 2 of Guedel’s Signs. (7)

Answer 7

Excitement - unconsciousness, muscle tone increased, eye movements increased, breathing erratic, delirium occurs.
Caused by the anaesthetic reaching the brain.

Question 8

Describe stage 3 of Geudel’s signs. (5)

Answer 8

Surgical anaesthesia - muscle tone relaxes, no eye movements, breathing slowing. When the surgery occurs.

Question 9

Describe stage 4 of Geudel’s signs. (5)

Answer 9

Respiratory paralysis - flaccid, no eye movements, respiratory effort stops, death if not ventilated.

Question 10

Describe the concept of MAC. (8)

Answer 10

Minimum alveolar concentration.
The [alveolar] at which 50% of patients fail to move to surgical incision when unpremeditated, and on 1atm of drug given inhalationally with O2 and air.
It is a measure of volatile anaesthetic potency.
At equilibrium, [alveolar] = [spinal cord].

Question 11

Name 7 things that affect MAC and say in which direction they will change it. (14)

Answer 11

Age (higher in infants, lower in the elderly)
Hyperthermia (increased), hypothermia (decreased)
Pregnancy (increased)
Alcoholism (increased)
Central stimulants (increased)
Other anaesthetics or stimulates (decreased)
Opioids (decreased).

Question 12

Describe the concept of a blood gas partition. (3)

Answer 12

How much the drug likes being in the blood.

Low value means fast induction and recovery because the drug gets quickly to the brain.

Question 13

Describe the concept of oil gas partition. (3)

Answer 13

How lipid soluable a drug is.
Determines potency and the amount of drug needed eg in fat people.
Less lipid soluable = more potent.

Question 14

Describe why nitrous oxides is often given with anaesthetics. (2)

Answer 14

It lowers the MAC of other anaesthetics so less of the other drugs needs to be given.

Question 15

Describe the stepwise pathway of GABA receptor inhibitors. (3)

Answer 15

Anxiolytics > sedation > anaesthetics.

Question 16

Describe which anaesthetics act on GABA receptors and which act on glutamate receptors. (3)

Answer 16

Xe, N2O and Ketamine act of glutamate.

All others act on GABA.

Question 17

Describe the four targets in the brain for anaesthetics and Explain why they are targeted. (8)

Answer 17

Reticular formation - to lower consciousness
Hippocampus - memory depression
Brainstem - respiratory and some CVS centres depressed.
Spinal cord - dorsal horn depressed for analgesia.

Question 18

Describe the common characteristics of local anaesthetics. (4)

Answer 18

Lipid soluable - more = greater potency
pKa relative to time of onset - more alkali (lower pKa) = faster onset
Chemical links - Ester = faster metabolism, aside = slower.
Protein binding - more bound = linger duration.

Question 19

Describe the procedures commonly done under local anaesthetic. (5)

Answer 19

Dentistry 
Obstetrics 
Patient-awake regional surgery 
Post-op pain management 
Chronic Pain management.

Question 20

Give three examples of local anaesthetics. (3)

Answer 20

Lidocaine, procaine, bupivacaine.

Question 21

Describe the structure of local anaesthetics. (3)

Answer 21

Aromatic ring linked (Ester or amid link) to an amino group.

Question 22

Describe the effect that adrenaline has on local anaesthetics. (3)

Answer 22

Increases duration of action and decreases spread because it vasoconstricts.

Question 23

Describe the common side effects of anaesthetics. (5)

Answer 23

PONV
CVS - hypotension 
PODC (delirium and confusion) 
Chest infection 
Anaphylaxis

Question 24

Describe the Mallampati Scoring system. (5)

Answer 24

How much soft palate you can see when trying to intubation. 
I - complete soft palate visible 
II - Complete uvula 
III - only base of uvula 
IV - no soft palate

Question 25

Describe the Cormack-Lehane Classification. (7)

Answer 25

How much you can see on direct laryngoscopy following head tilt chin lift, and external laryngeal manipulation. 
I - full view of cords
II - epiglottis only 
III - top of epiglottis 
IV - nothing.