inhalation sedation

Question 1

Properties of Nitrous Oxide

Rapidly absorbed but relatively insoluble in blood.

Answer 1

1. quick onset
2. quick recovery - leaves circulation and exhaled through lungs

Question 2

Properties of Nitrous Oxide

Weak Anaesthetic:

Answer 2

1. wide margin of safety - little effect on the respiratory system and excreted unchanged so suitable for pts with liver or kidney disease.
2. loss of consciousness extremely unlikely

(not suitable to anaesthetise so will still require LA)

Question 3

Nitrous Oxide Mechanism of Action

Answer 3

1. anxiolysis - enhances activity of GABA receptors (similar to benzodiazepines) to stabilise nerve cell membrane.
2. analgesia - mediated through interaction with opioid receptors.
3. euphoria - dopamine release but has a mixed response (subjective to the individual).

Question 4

Plane I of Analgesia - 5-25% NO

Answer 4

• relaxation and general sense of wellbeing
• paraesthesia
• feeling of suffusing warmth
• alert and readily responds to questions
• slight reduction in spontaneous movements
• decreased reaction to painful stimuli
• normal pulse, blood pressure, respiratory rate, reflexes and pupil reactions

Question 5

Plane II of Analgesia - 20-55% NO

Answer 5

• marked relaxation and sleepiness
• detached from environment
• altered senses
• possible dreaming
• widespread parasthesia, moderate analgesia
• reduced gag reflex
• delayed response to questions
• vital signs and laryngeal reflexes should be unaffected

Question 6

Plane III of Analgesia - 50%+ of NO

Answer 6

• marked relaxation and sleepiness, glazed appearance
• complete analgesia
• nausea and dizziness common
• pt may vomit
• unresponsive to questions
• may lose consciousness and enter stage 2 of general anaesthesia

Question 7

Positives of Nitrous Oxide

Answer 7

• anxiolysis
• mild analgesia
• hypnosis
• euphoria
• rapid induction and recovery
• minimal metabolised

Question 8

Negatives of Nitrous Oxide

Answer 8

1. systemic toxicity - long term occupational exposure can lead to haematological, neurological and reproductive side effects.
2. environmental effect - 300x more impact on global warming than CO2.

Question 9

Ways to minimise nitrous oxide pollution:

Answer 9

1. active scavenging systems (miniscav)
2. room ventilation - 15 changes of room air per hr.
3. floor level extractor fans
4. correct technique:
   - check pt is continuing nasal breathing
   - monitor mask seal
   - use lowest amount required for tx
   - rubber dam
5. regularly serviced equipment

Question 10

Patient Suitability

Answer 10

• mild to moderate dental anxiety
• some degree of cooperation
• > 5 years old (needs to sit by themselves in the dental chair)
• acclimatisation prior to sedation
• able to understand the same language

Question 11

Contraindications

Answer 11

1. URTI (upper respiratory tract infection)
2. blocked nose
3. chronic respiratory disease
4. mouth breathers
5. pre-cooperative children
6. unable to speak and understand the same language
7. moderate to severe learning disabilities
8. first trimester of pregnancy
9. upper anterior apicectomy

Question 12

Information for Patients and Parents

Answer 12

• clear description of IHS using nitrous oxide and oxygen
• pt remains awake throughout procedure
• LA will still be used
• show the nasal hood
• explain how they will feel
• breathing exercises to practice prior to appt
• alternative options

Question 13

Pre-op Instructions

Answer 13

(verbal and written instructions should be given re. post-op care)
- light meal 2 hours before appt
- children to be accompanied by responsible adult
- transport home - car or taxi
- no bike riding/machinary op for rest of the day
- adult supervision for the rest of the day, don’t return to school

Question 14

IHS Consent Process

Answer 14

• carried out prior to the day of appt
• consent form 2 on clinic
• signed by adult with PR
• info given verbally and in written format
• discuss other options
• confirm tx to be undertaken with NO and O2 +/- LA

Question 15

Pre-Op Machine Checks

Answer 15

• done each day/session to make sure machine is working correctly to confirm safety
• check reservoir bag is inflating with no leaks
• start with 100% O2, then 50% to check flow readings correspond
• remove O2 supply and check NO flow immediately stops

Question 16

On Pt Arrival:

Answer 16

1. RMH
2. check consent
3. adult present to accompany home
4. has the pt eaten
5. child able to breathe freely through nose
6. toilet?

Question 17

Clinical Procedure

Answer 17

1. Place and secure appropriately sized nasal hood, check for leaks.
2. Start flow rate at 6l/min (depends on size of child)
3. 100% O2 for 1 min to check adequate nose breathing and cooperation
4. Incremental changes - 10% per min up to 80% and then 5% per min, titrated appropriately until sedation achieved.
5. Calm relaxing voice with child-friendly language
6. Tell a story and reassure.
7. Carry out tx and monitor sedation, responding accordingly.
8. 100% oxygen for over 3 mins at the end to prevent diffusion hypoxia.

Question 18

Things to monitor throughout:

Answer 18

• observe that the bag moves as they breathe in and out.
• guide pt with breathing if done too quickly/deep/shallow
• look for subtle changes

Question 19

How the pt will feel:

Answer 19

• floating
• distant
• tingling
• more relaxed
• sleepy
• decreased reaction to painful stimuli

Question 20

Signs of Oversedation

Answer 20

1. persistent mouth closing (or difficulty opening mouth on request)
2. spontaneous mouth breathing
3. pt feels unpleasant
4. nausea / vomiting
5. sluggish and irrational response
6. incoherence
7. decreased cooperation
8. laughing, crying, giddiness

Question 21

How to treat oversedation:

Answer 21

1. decrease NO concentration by 5-10%
2. reassure and explain the pt will feel better soon, LOTS OF ASSURANCE
3. keep nasal mask in place

Question 22

At the end of the procedure:

Answer 22

1. administer 100% O2 for at least 3 mins
2. allow them to remain in the chair for another 10
3. check pt is coherent, standing steady and can walk unaided
4. post op instructions after recovery

Question 23

What is Diffusion Hypoxia?

Answer 23

• low solubility of NO in the blood/tissues results in rapid outflow of NO from the blood across the alveolar membrane when the incoming gas flow is stopped.
• results in dilution of the inspired oxygen concentration and hypoxia.
• prevented with 100% O2 at the end of the procedure for at least 3 mins

Question 24

Safety Features

Answer 24

1. colour coded - blue for NO, white for O2.
2. pin index - ensures O2 and NO are connected to the correct fixings.
3. oxygen fail safe mechanism - NO flow is only allowed via an opened valve when there is flow of oxygen to the system, O2 is less than 30% then NO stops.
4. air entrainment valve - allows the flow of atmospheric air should the gases run out.

Question 25

Active Scavenging

Answer 25

• to collect and remove excess gases to prevent them from being vented back into the operating room.
• pt breathes out of nose, white gases removes through the system and out of the building.
• 45 litres/min

Question 26

If the bag is too tight / collapsing on the IHS machine, what does this mean?

Answer 26

too tight = too much O2
collapsing = not enough O2

Question 27

Which gas is in the blue cylinder?

Answer 27

nitrousoxide

Question 28

Which enzyme can NO cause the inhibition of?

Answer 28

methionine synthase
(caused of B12 deficiency)