N2O Inhalation Sedation

Question 1

Indications for IHS

Answer 1

Dental anxiety
Young age
Short procedures
ASA I-II
Needlephobia

Question 2

Contraindications for IHS

Answer 2

ASA III+
Nasal obstruction/snoring/apnoea
Lengthy surgical procedure
Extreme anxiety
Behavioural issues

Question 3

Functional properties of N2O

Answer 3

Anxiolytic
Mild analgesic
Hypnotic
Odourless/colourless

Question 4

Chemical properties of N2O

Answer 4

Low solubility/low blood-gas coefficient 0.47
High MAC 105%
Low partial pressure
Fast recovery
No metabolites

Question 5

N2O pressure of storage
N2O gravity

Answer 5

43.5 Bars
Gravity of 1.53

Question 6

Physical effects of N2O

Answer 6

CNS depression
Mild respiratory depression
Minimal effect on CVS

Question 7

Mechanism of analgesia N2O

Answer 7

Interacts with opioid receptors in mid brain
Triggers peptide release
Mild depression CNS

Question 8

Mechanism of anxiolysis N2O

Answer 8

Interacts with GABA receptors
Suppressed nervous system activity

Question 9

Small increase in [N2O] will lead to

Answer 9

Rapid increase in uptake and rise in partial pressure of gas in tissues

Question 10

Signs of sedation

Answer 10

Conscious
Light headed/dissociating/partial analgesia
Lethargy
Warm feeling
Vital signs normal
Normal response to verbal comments
Reduced gag reflex
Reduced response to stimuli
Tingling/relaxed feeling

Question 11

Signs of oversedation

Answer 11

Loss of verbal contact
LoC
Loss of cooperation
Nausea/vomiting urge
Increased heart rate

Question 12

Oversedation is managed by

Answer 12

Reducing N2O by 5-10%
Monitoring signs and symptoms
Continuing or postponing treatment

Question 13

Stages of sedation

Answer 13

Plane 1-3

Question 14

Plane 1

Answer 14

5-25% N2O
Awake
Gag reflex slightly reduced
Tingling/relaxed feeling

Question 15

Plane 2

Answer 15

30-50% N2O
Dreamy look/light/heavy feeling

Question 16

Plane 3

Answer 16

50%+ N2O
Total analgesia
Loss of contact/LoC
Loss of cooperation

Question 17

N2O technique is

Answer 17

Semi-hypnotic
Produces physiological changes whilst maintaining reflexes

Question 18

Advantages of N2O

Answer 18

Rapid 2-3 minute onset
Rapid 3-6 min recovery
Flexible duration
No adverse effects on system

Question 19

Disadvantages of N2O

Answer 19

Space required
Technique sensitive
Relies on patient co-operation

Question 20

Hazards - Types

Answer 20

Reproductive
Neurological
Haematological

Question 21

N2O main adverse effect

Chemical effect

Answer 21

Oxidation of B12 cobalt ion

Question 22

Oxidation of B12 affects action of - which is in involved in -

Answer 22

Methionine synthase
DNA synthesis

Question 23

Adverse effects of N2O

Answer 23

Reduced DNA synthesis
Bone marrow suppression
Hepatic disease
Reproductive issues
Diffusion hypoxia - N2O displaces O2 in alveoli - 100% inspired N2O

Question 24

Maximum recommended exposure for clinicians

Answer 24

100ppm over 8 hour period