IHS key points Flashcards
indications
mild/mod anxiety needle phobia hyper gag reflex multiple quadrant tx in young kids traumatic procedures medical conditions aggravated by stress - asthma unaccompanied adults requiring sedation age (can understand) ASA1 preventively for traumatic procedures or ortho ext - esp if no tx experience
contraindications
may not match their coping style (monitor) common cold mouthbreather extreme anxiety tonsillar/adenoidal enlargement severe COPD 1st trimester pregnancy? fear of "mask"/claustrophobia pts with limited ability to understand unsuccessuful prev attempt NM disease e.g. myesthenia gravis, MS
age cut off
no absolute, generally 7yrs and over prev experience maturity understanding pt prep by parent
equipment
gas cylinders - blue N2O - black with white top O2 - may be piped gases in hospital pressure reducing valves flow control meter reservoir bag gas delivery hoses nasal hood waste gas scavenging system
quantiflex O2 flow meter
measures flow rates of up to 10l/min
readings taken from equator of ball
accuracy +/- 5%
white meter
air entrainment valve
if gases fail valve opens - allows room air into circuit
they can continue to breathe if machine switches off
mixture control dial
tells you % O2 - can’t turn it lower than 30% (safety)
flow control knob
how many l/min
nitrous oxide flow meter
blue
measure flow rates of up to 10l/min
read centre of ball
accuracy +/- 5%
O2 flush button
flushes O2 35l/min
v fast O2 delivery
emergency use only
reservoir bag
2/3l bag, rubber or silicone
- smaller available for children
full of air and O2
bag should move visibly with each inspiration and expiration
helps to monitor respiration - emulates pts lungs
- helps you know what flow rate to give them
- must not collapse - need to increase flow rate
- if stuffed - reduce flow rate
want 12-16 breaths/min
gas delivery hoses
2.5cm diameter, corrugated
universal joints
one hose delivers fresh gases from machine
one hose delivers waste gas to scavenging system
non-return valve in expiratory limb prevents rebreathing expired gases
single use breathing circuits - tubing and mask
nasal mask/hood
various sizes
should form a seal around nose (gases shouldn’t escape)
2 connections to breathing circuit
pin index system
prevents wrong cylinder being attached
can’t attach wrong gas
diameter index system
prevents cross-contamination of piping
minimum O2 delivery
30%
O2 fail safe
operates when O2 pressure <40psi
if O2 runs out machine switches off
scavenging system
external to the quantiflex machine or piped gas system
active scavenging of waste gases - small negative pressure (so they get sucked away)
changing surgery air reduces N2O levels - 15 changes of room air per hour
watch for pt mouth breathing
- expelling waste gas into atmosphere not system
check mask seal to reduce contmination
use dam - reduce mouth breathing, reduce some of waste gas expelling
safety features of quantiflex
air entrainment valve O2 flush button O2 monitor - see what they are receiving reservoir bag - emulate pt lungs colour coding - pin index system scavenging system O2 and N2O pressure dials pressure reducing valves one way expiratory valve quick fit connection for positive pressure O2 delivery 2 tanks esp for O2 - back tank is a reserve - so you always have enough O2 minimum O2 delivery 30% O2 fail safe - if runs out machine switches off
advantages
rapid onset 2-3mins
rapid peak action 3-5mins
depth altered either way - can turn sedation up and down
flexible duration
rapid recovery when N2O turned off
no injection (but may need LA)
few SEs, safe
drug not metabolised
some analgesia (better for ischaemic than inflammatory)
- fingers and toes a bit tingly/numb
no amnesia - in future may be happy to do without sedation
disadvantages
£ equipment £ gases space occupying equipment not potent, need cooperation - just helps them cope a bit - won't disarm a pt who isn't wanting tx requires ability to breathe through nose chronic exposure risk? staff addiction difficult to accurately determine actual dose - accuracy not great +/- 5% - if pt speaks to you they are breathing through mouth - leakage if nasal hood not fitting less muscle relaxation
signs of adequate sedation
pt relaxed/comfortable - feeling like just before you fall asleep pt awake low blink rate laryngeal reflexes unaffected vital signs unaffected gag reflex reduced mouth open on request decreased reaction to painful stimuli (LA easier) decrease in spontaneous movements verbal contact maintained
symptoms of adequate sedation
mental and physical relaxation lessened awareness of pain paraesthesia - lips, fingers, toes, legs, tongue - tingly lethargy euphoria detachment 'floating feeling' warmth (take jackets off first) altered awareness of passage of time dreaming (daydream) small controllable "fit of the giggles"
if have anxious parent what can you get them to do?
watch the bag
pre-op instructions to parent and child
have a light meal before appt take routine meds as normal children accompanied by competent adult - be aware pregnant women can't be in surgery while IHS - only child having IHS allowed in surgery adults accompanied at their first appt - after can attend alone no alcohol on day wear sensible clothing arrange childcare during and after appt if have cold blocking nose cancel appt plan to remain in clinic for up to 30mins after tx
monitoring during tx
clinical - don’t need electronic
keep talking to pt - agree with nurse in advance
- nodding/thumbs up response
if pt oversedated:
increase O2 in 5-10 % increments until adequate
if pt undersedated
reduce O2 in 5% increments until satisfactory
technique
set up machine
select nasal hood (size in notes)
connect to hoses
set mixture dial to 100% O2
settle pt in chair, reinforce explanations of procedure
set flow to 5-6l/min
position hood and encourage nasal breathing
check reservoir bag movements
pt to be comfortable with hood for 1min
reduce O2 by 10%
ask pt to signal when begin to feel different
wait 1min and repeat
after O2 reaches 80% reduce by 5% per min
stop titration when pt ready for tx
- keep asking pt
constant reassurance and hypnotic suggestion
- visualisation
- behavioural management
- suggest to them that they feel comfortable, dreamy
- quiet calm voice
monitor for S+S of adequate sedation
adjust level of O2 as required
too small reservoir bag movements
check seal and look for mouth breathing
+/- reduce flow
too large reservoir bag movements
increase flow rate
diffusion hypoxia
can occur with administration of inadequate O2 during/immediately after N2O anaesthesia
influences PO2 within alveolus
theoretical risk - doesn’t happen as equipment always delivers enough O2
success
50-90%? difference - pt pop - greater success for ortho ext (motivated) - poorer in pts with pain - appropriate pt assessment/selection
at end of tx
recovery - gradually increase O2 by 10-20% per min or turn straight to 100% - doesn’t make a lot of difference
administer 100% O2 2-3mins to prevent diffusion hypoxia
remove hood and turn gas flow off
return pt to upright slowly, give praise and reassurance
after tx
adult pts may leave unaccompanied at dentist’s discretion
<16yrs need competent adult
before discharge
- ensure they feel normal before they stand up/leave
- ask how pt felt procedure went
pt may feel shivery after IHS
- reassure pt common/normal and passes quickly
- put jumper back on
- “like after you finish a race”
physical properties of N2O
sweet odour, pleasant to inhale, non-irritant
- nasal hoods - strawberry, orange
liquid in cylinders, pressure constant until all liquid evaporates
low tissue solubility so rapid onset and fast recovery
MAC value in excess of 1atm so GA without hypoxia impossible
mild analgesic hence term relative analgesia (RA), still need LA
N2O adverse reactions
hypoxia malignant hyperpyrexia (controversial) - AR trait - muscle contracture - acidosis - hyperkalaemia - hyperpyrexia loss of protective reflexes diffusion hypoxia pressure/vol effects - ear - tinnitus psychological - euphoria - hallucinations - claustrophobia fire headache, paraesthesia, tingling
concenctrations of N2O
10-30%
don’t go beyond 30% N2O
complications - pt
nausea/vomiting
unintentional LOC
- rare as titrated so slowly, usually related to: extreme young age of child, polypharmacy, use of multiple drugs
complications - staff
toxicity: esp B12 suppression
staff addiction
anaesthetic agents - controlling exposure under COSHH legislation
no evidence N2O exposure causes developmental defects in foetus or any other reproductive health effects
animal and lab studies - “exposures of ≥1000ppm for ≥8hrs per day suggest inhibition of new cell production”
occupational exposure standard - 100ppm over 8hr TWA period
- 1/5 of the exposure level at which effects were seen in animals
studies show it reduces fertility if have excessive levels
control of occupational exposure to N2O in dental surgery
a properly maintained gas delivery system
a scavenging nosepiece - fits well “tiger marks”
vented suction (scavenging) machine
fans to sweep air away from the operator
rubber dam to minimise pt speech
minimise pt speech
= without these the air in the surgery can contain 500-6700ppm
toxicity of NO to dentists
liver disease miscarriage bone marrow suppression addiction carcinoma birth defects
advanced IV sedation - propofol
12+ years
target controlled infusion sedation - titrate
anaesthetist administered
useful for v long or v short procedures
can be increased or decreased for particular bits
mean rapid onset and recovery
POIs - verbal and written
due to effects of sedation may have amnesia
adult knows how to care for you
will be slightly drowsy, go home and rest
DON’T
- ride bike/active sports/training
- pour boiling water into a cup
- do a job involving unguarded machinery
- take alcohol
- take sedative drugs without medical advice
- make important decisions
be careful on social media as you may be a bit muddled and lack judgement
