Inhalation Sedation Flashcards
Define conscious sedation
A technique in which the use of a drug or drugs produces a state of depression of the CNS enabling treatment to be carried out.
Both verbal contact and protective reflexes are maintained in the patient throughout the period of sedation.
The drugs & techniques used to provide conscious sedation for dental treatment should carry a margin of safety wide enough to render loss of consciousness unlikely.
Why is sedation needed?
Fear
50% children moderately anxious, 10% extremely anxious
Deaths from GA
What are the sedation techniques?
Inhalation - nitrous oxide/oxygen, sevoflurane
Intravenous - midazolam, propofol
Transmucosal - midazolam (intranasal, buccal)
Oral - temazepam, diazepam, midazolam, katamine
Intramuscular - ketamine
Combo of above
Nitrous oxide features?
Recreational use
Deaths due to hypoxia
Properties of nitrous oxide?
Volatile
Denser than air - 1:1.5
Less potent - Min amount of gas to give 50% of population to not feel pain as has a MAC50 of 104
Often used in anaesthesia as carrier/induction gas
Poorly soluble - rapid onset/rapid recovery
Pharmacokinetics of nitrous oxide?
Inhaled into lungs with oxygen through nasal mask Travels down partial pressure gradient Alveolus to capillaries Hardly metabolised - 0.004% Excreted through lungs Elimination half life - 5 mins
Pharmacodynamics of nitrous oxide/oxygen sedation?
Analgesic
Anaesthetic
Hypnotic
Anxiolytic - GABA
What are the stages of anaesthesia?
- Analgesia
- Plane 1:
Moderate sedation and analgesia (5-25% N20)
- Plane 2:
Dissociation sedation and analgesia (20-55% N20)
- Plane 3:
Total analgesia (50-70% N20) - Excitement
- Surgical analgesia
- Respiratory paralysis
Signs that the sedation is adequate?
Awake Feels relaxed Suggestive state Giggling Verbal responses Maintaining mouth open Reduced blink rate Spontaneous respiration
Signs of over sedation?
Pt no longer enjoying effects Hysterical laughter, tears Decreased cooperation Nausea/vomiting Mouth closing - repeatedly Snoring Incoherent speech Irrational and sluggish responses Loss of consciousness
Indications for inhalation sedation?
Social
- Mild anxiety/needle phobias/gagging/fainting
- To enable cannulation
Medical
- Conditions aggravated by stress
- Conditions where continuous oxygen delivery is beneficial
- Conditions which affect co-operation
Dental
- Unpleasant procedures
- Avoid GA in medically compromised
Contraindications of inhalation sedation?
Social
- Severe anxiety/ claustrophobia/ no consent/lack of escort
- Lack of understanding
Medical
- Blocked nose/URTI/ unable to nose breathe
- Recent eye/ middle ear / sinus / intracranial surgery
- Bleomycin therapy (chemotherapy drug) / myaesthenia Gravis
- Pregnancy - 1st and 3rd trimesters
Dental
- Traumatic procedures /unsuitable for LA alone
- Tx on upper anterior teeth - lip trapped
Safety checks for inhalation sedation?
- Pin index = prevents oxygen and nitrous oxide mixing up
- Scavenging at 40L/minute = actively removes air at the level of the nose mask
- Nasal mask and tubing
- Oxygen failsafe = if O2 stops the N2O will also stop
- Max 70% N2O
- Oxygen flush = delivers 30L of oxygen in a second (only used in emergency)
- Air entrainment valve = allows pt to breathe air from atmosphere
- Reservoir bag
Nitrous oxide/oxygen pre-op instructions?
Light meal
Take routine medicines as usual
Children must be accompanied to and from their appt by a competent adult
Do not bring other children
Can cause dizziness /nausea/ headaches at higher doses
Steps of inhalation sedation?
Safety checks, consent, check escort
Introduce to child (happy gas)
Start O2 and turn up flow rate (5-6L/min)
Fit mask and encourage nose breathing
Titrate N20 - 10% per min to 30% and then 5% per min until sedation
Hypnotic suggestion, clinical monitoring
100% O2 minimum of 3 mins to recover
What is diffusion hypoxia? How does it occur?
Nitrous oxide poorly soluble in blood so when you stop giving it the partial pressure decreases in the lungs and the gradient changes = nitrous oxide into lungs
= If no oxygen lungs are full of nitrous oxide = diffusion hypoxia
Record keeping for inhalation sedation?
Consent and escort Safety checks completed Second appropriate person (dental nerve) Mask size Flow rate Max dose Response/ level of co-operation Recovery time
How to reduce the amount of Nitrous oxide gas we are exposed to?
COSHH exposure limits - 100ppm TWA over 8 hours
Active scavenging at 45L/min
- Statutory requirement in UK
- At level of nasal hood
Passive scavenging
- Floor level extractor fan, opening window
Supplementary high volume aspiration
Rubber dam
- Inconclusive but seems logical
Well fitting mask
Good technique - reduce mouth breathing / conversion / titrate carefully
Good initial pt assessment
Haematological occupational hazards with inhalation sedation?
N2O oxidises vitamin B12
Inactivates methionine synthase
Impairs DNA synthesis, affecting haematopoesis
Pernicious anaemia
Neurological occupational hazards with inhalation sedation?
Methionine essential for myelin synthesis
Peripheral neuropathy
Spinal cord degeneration / myelopathy
Other occupational hazards with inhalation sedation?
Hepatic disease
Renal disease
Cytotoxicity
Malignancy
What does the cumulative effect of inhalation sedation depend on?
Pattern of exposure
Tissue sensitivity
Vitamin B12 intake and stores
Extent to which methionine synthase is deactivated
Evidence for N2O/O2 sedation?
Success
Shaw et al, 1996 –
- 90% of children aged 4-17 years manage extractions successfully with LA and N2O/O2 sedation
- 97% of parents and children satisfied
Time
Wilson et al, 2007 -
- Takes an average of 7 mins to reach adequate sedation
Cost
Jameson et al, 2007 -
- 245.47 per patient for dental care under advanced conscious sedation
- 359.91 per patient under GA
