Inhalation Sedation Flashcards
What does ‘A Conscious Decision’ state?
GA can only be completed where critical care are available
Who raised concerns about the safety of GA in dental practices?
Poswillo Report 1990
What are some examples of behavioural , cognitive and physiological ways anxiety can present?
Behavioural
Dental avoidance or irregular attendance- to avoid anxiety- provoking area
Disruptive/aggressive behaviour- anxiety manifest itself with disruptive comments
Cognitive
Over-estimate the threat/consequences
Expect failure
Low self-esteem
Physiological
Increased heart rate
Increased breathing rate
Perspiration
Muscle tension/ clenching
Dryness of mouth
Butterflies in the tummy
Dizzy/feel sick
What is conscious sedation - the definition?
A technique in which the use of a drug(s) produces a state of depression of the CNS enabling treatment to be carried out, but during which verbal contact is maintained throughout
The drugs and techniques used should carry a margin of safety wide enough to render loss of consciousness unlikely.
what are the properties of ideal sedation?
? Amnesia - limited memory of tx → Don’t want to forget positive experience à reinforce behaviour. Don’t want to recollect negative experience
Acceptability - easily accepted by pt
Analgesic - give some pain control (mask LA)
Anxiolytic - effectively ease anxiety
Compatibility – minimum interaction with other drugs/other systems (i.e. CV, resp)
Cost - inexpensive
Rapid Action - rapid onset and rapid recovery
Safe - wide margin of safety, no adverse side effects, reversible (inappropriate response to agent will need reversal)
Simple - easy to administer and titrate (adjust dose of agent to match level of anxiety, give min. required)
What are the properties of nitrous oxide?
Colourless gas at room temperature
Non-flammable (but does support combustion)- careful around naked flame
Non-irritant to mucosa- good to go through nasal passages
Relatively insoluble in blood
Slightly sweet odour
Stored as a liquid in blue cylinders at 750 psi
x1.5 the density of room air
NO is heavier than room air will sink to the bottom and be at ground level
How does N2O work?
!1) Inhalation of N2O
2) Raised partial pressure of N2O in lungs
3) N2O forced into bloodstream across alveolar membrane N2O carried to brain
4) Gas exchange within the brain
What are some clinical effects N2O
Analgesia (mild effect)- but need LA
Depresses the CNS
Euphoria
Relaxation
Mild on respiratory (slow down breathing rate)
Mild effect on CV system → slight vasodilation
Good for IV sedation, easier to cannulate
Paraesthesia (tingling)
Rapid onset of effects- few mins
Sedation (dissociation)
Therapeutic dose: 50-70% used
Unlikely to see side effects: nausea, headaches
What is diffusion hypoxia? and how would you avoid it?
When you turn off N2O…
Rapid elimination of N2O from the blood
Large volumes of N2O enter the lungs
Can displace O2 from the alveoli → diffusion hypoxia (drop in O2 sats)
Avoid by: giving 100% O2 for >3mins
What are the acute and chronic adverse effects of N2O?
Acute: hypoxia, nausea, dizziness
Chronic: staff exposure, substance
What are the advantages of inhalation sedation?
Can regulate depth of sedation via titration
Easily reversed with 100% O2
Minimal effect on cardio-resp system
Minimal interaction with other drugs
Rapid onset and recovery
Simple, non-invasive - good for needle phobics
What are the disadvantages of inhalation sedation?
Nasal mask not always accepted - claustrophobic
Nasal hood can interfere with tx - sits on upper lip
Need continuous N2O delivery
Nitrous oxide pollution
Some degree of patient compliance required - children need to engage with the story being told, won’t work if pt fighting effects
Cost of equipment
What are the HSE recommendations?
Exposure limit of 100ppm for a time-weighted average 8-hour period
Active scavenging 45l/min (excess gases physically removed and well ventilated surgery, good surgery flow and well-fitted nasal hood, minimal talking from pt to prevent gas leaking)
Good technique using minimal effective dose
Risk assessment for pregnant staff
What are some indications for using N2O?
Gag reflex
Medically compromised pt (ASA score and GA too risky)
Mild to moderate dental anxiety
What are some contraindications for N2O?
Blocked nose - mouth breathers - will in ineffective
Chronic respiratory disease - rely on low O2 drive, 100% O2 could cause problems
Methotrexate - N2O can potentiate effect on folate metabolism, liaise with rheumatologist
Bleomycin - risk of respiratory failure if given O2 > 25%
Pre cooperative children e.g unable to respond to commands or verbal suggestions
Ocular , mid-ear surgery → avoid giving pressure in any filled space
Pregnancy - defer until after breastfeeding unless emergency
URTI - if transient wait to rebook
Very anxious pt
