conscious sedation Flashcards
what is the difference between exogenous and endogenous dental anxiety?
exogenous: from adverse experience (indirect or direct)
e.g childhood traumatic experience, through family members, parental fear
endogenous: genetic or physiologically determined
what is conscious sedation?
the use of drugs produces a state of depression of the central nervous system to allow treatment to be carried out. verbal contact with the patient is maintained throughout.
use of drugs with side safety margins so loss of consciousness is unlikely
what drugs are used for premedication (anxiolytics)?
diazepam
lorazepam
what drugs are used for inhalation sedation?
nitrous oxide
oxygen
what drugs are used in intravenous sedation?
midazolam
propofol (TCI, PCI)
opioid and midazolam (fentanyl)
ketamine
what drugs are used for intranasal sedation?
midazolam and lidocaine (offlicense)
what drugs are used for oral sedation?
temazepam
midazolam (offlicence)
what drugs are used for rectal sedation?
midazolam
what are common side effects of GA?
- pain during injedction of drugs
- bruising and soreness from canula
- aches, pain & backache
- sore throat; damage to lips and tongue
- dizziness, blurred vision
- headache, confusion or memory loss
- bladder problems
- itching
what are some uncommon side effects/complications of GA?
- chest infection
- damage to cornea of eye
- existing medical condition getting worse
- awareness (becoming conscious during operation)
what are some rare/very rare complications of GA?
- damage to eyes including loss of vision
- heart attack or stroke
- serious allergy to drugs
- nerve damage to nerves in the spine
- equipment failure causing significant harm
- death
what is the scientific association between anxiety and pain?
anxiety and fear activate the pituitary adrenal axis which leads to an increased experience of pain
what are some ways of managing pain pre-procedure?
- reassurance
- behavioural management techniques: desensitisation, tell-show-do, progressive relaxation
- oral premedication
- music therapy
- hyponosis
- CBT
what are some medical indications for conscious sedation?
factors affecting ability to co-operate:
* parkinson’s disease, cerebral palsy
* (uncontrollable shake that can worsen with stress)
* failure to keep still
factors that are potentially aggravated by stress
* hypertension, angina (white coat syndrome - stress=higherBP)
* epilepsy, asthma, psychosomatic disease
what are some behavioural indications for conscious sedation?
uncontrollable gagging, large tongues
* previous episodes of choking
persistent fainting with LA use
failure of LA
* psychological unless there is infection
believe treatment is painful
* overreaction to noises
what are some contraindications to sedation?
medical conditions affecting cooperation
* learning disabilities - varying with severity
* pregnancy - should NEVER sedate
* blockage of nasal airway - can IV, not IS
* chronic respiratory disease
* myasthenia gravis
* severe psychiatric disease - may flare up
what is MDAS?
modified dental anxiety scale
* 5 questions on anxiety
* completed before treatment
* gives score out of 25
what is ASA? what is in each category?
physical status clsasification system
ASA I - normal healthy patient
ASA II - mild systemic disease - does not limit lifestyles
ASA III - severe systemic disease - limits activity but not incapacitating (angina during exercise)
ASA IV - severe systemic disease - constant threat to life, incapacitating (uncontrolled angina at rest)
ASA V - moribund patient - not expected to survive without operation (ludwigs angina)
ASA VI - declared brain dead patient - organs are being removed for donor purposes
what ASAs would be accepted for sedation in primary care?
ASA I & II
what ASAs would be accepted for sedation in specialist care?
ASA III & IV
what is the interaction of alcohol with benzodiazepines?
enhanced sedative effect
what is the interaction of analgesics (opioids) with benzodiazepines?
enhanced sedative effect
what is the interaction of anti-bacterials with benzodiazepines?
erythromycin inhibits metabolism of midazolam
what is the interaction of anti-depresssants with benzodiazepines?
enhanced sedative effect
what is the interaction of anti-epileptics with benzodiazepines?
BDZs reduce effect of some anti-epileptics
what is the interaction of anti-histamines with benzodiazepines?
enhanced sedative effect
what is the interaction of anti-psychotics with benzodiazepines?
enhanced sedative effect
what is the interaction of anti-hypertensives with benzodiazepines?
enhanced hypotensive effect
what is the interaction of anti-ulcer drugs with benzodiazepines?
cimetidine inhibits metabolism of BDZ
how do you carry out an airway assessment?
LEMON
Look externally
Evaluate with 3:3:2 rule
Mallampati classification
Obstruction (obesity)
Neck mobility (straight line to trachea)
what is the 3:3:2 rule?
3 fingers between incisors
3 fingers under mental (chin)
2 fingers submental
what is mallampati classification?
how open is the oropharynx? visibly?
what are the risks of high BMI in conscious sedation?
- blood pressure
- absorption of drugs
- regurgitation
- difficult airway
- difficult cannulation
what is IOSN and what does it take into account?
indicator of sedation need
- treatment complexity
- medical and behavioural complexity (ASA)
- dental anxiety (MDAS)
how is treatment complexity given a score for IOSN?
- routine - scaling, single rooted XLAs, single Q restoration, anterior endo
- intermediate - RSD, multi rooted XLAs, surgical XLA without bone removal, anterior apicectomy, 2 Q restorations
- complex - perio surgery, surgical XLA w bone removal, posterior apicectomy, multiQ restorations, posterior endos
- high complexity - more complex txs
what do the IOSN scores mean?
out of 12
- low (3-4) - no sedation indication, minimal need
- moderate (5-6) - no sedation indicated, moderate need
- high (7-9) - sedation indicated, high need
- very high (10-12) - sedation indicated, may require GA or sedation in secondary care
what are indications for IV sedation?
claustrophobia
* intolerant to masks
* bad experience with GA
extremely anxious patients
* IV more profound than IS
what are some contraindications to IS?
- medical conditions related to elimination of drugs (liver/renal disease)
- disorders affected by BDZs ( myasthenia gravis, COPD, bronchitis, emphysema
- needle phobia
- pregnancy
- nursing mothers
- children - unpredictable
- severe psychiartric disease
- CNS depressants - may be hyper sensitive
- obesity
- use of recreational drugs - increased tolerance
what are some advantages of IV sedation?
fast speed of onset
* 20 second
* rapid drug effect
ability to titrate to patient’s response
relative comfort
intravenous access is mantained
* useful if theres an emergency
recovery period
* shorter than oral or IM drugs
what are some disadvantages of IV sedation
uncomfortable to establish venous access
drug effects are very rapid
* side effects produced rapidly
* careful monitoring needed
* 45 minute operating window but can be shorter
adverse reactions are more severe than oral
once given drug cannot be recovered
* antagonists block effect - do not hasten elimination
* escort home needed as drug will not be eliminated before discharge
prolonged recovery
respiratory depression
what are the effects of benzodiazepines?
anxiolytic
* induces relaxation
sedative/hyponotic
* reduce level of consciousness
* reduced responsiveness, concentration
* slurring speech
muscle relaxant
* tremors, involuntary ms movement, ms spasticity
anticonvulsant
antero-grade amnesia
respiratory depression
xerostomia
tolerance and dependence
* longterm effectiveness reduced
* withdrawal when sudden cessation
drug interactions
sexual fantasy
paradoxical reactions
* agitation, aggression, restlessness, hyperactivity
what is midazolam?
what is the distribution and elimination time?
cautions?
water soluble benzodiazepine
distribution t : 6-15 minutes
elimiation t : 1.5-2 hours
shorter half life and faster onset of action than diazepam
caution use in children and elderly
* impaired enzyme function
* risk of prolonged sedation and overdosage
how do BDZ work?
BDZ enhances GABA activity
sensory nerves become less exitable
this reduced sensory input to brain
what drugs inhibit midazolam?
what is the effect of this
HIV protease inhibitors
* oral midazolam is contraindicated
azole antifungals
antibiotics
* ciprofloxacin, norfloxacin, erythromycin, clarithromycin
amiodarone
* affects metabolism
grapefruit juice
antidepressants
calcium channel blockers
H2 receptor blockers
these elevate serum concentration, prolong the elimination of the drug & therefore prolong patient recovery
what drugs induce midazolam?
what is the effect of this
herbal remedies
* st john’s wort used for mental health
corticosteroids
* dexamethasone, hydrocortisone, prednisolone, methylprednisolone
anticonvulsants
* carbemazepine, phenytoin
antibiotics
* rifampicin, rifabutin
HIV anti-retrovirals
* nevirapine
oral hypoglycaemics
these increase metabolism of the sedative drugs by inducing p450 enzymes therefore reduces the sedative effect
what instruction should you give to patients post-IV
care arrangement for older dependents or children
no driving/cycling, operating machinery or cooking for 24 hours
what are common complications of IV cannulation?
- venepuncture
- intra-arterial injection
- haematoma
- pain
how should venepuncture be treated
stop injection & remove cannula
apply pressure to disperse solution in the tissues
reassure patient
how should intra-arterial injections be recognised and managed
prevent by site selection
recognise:
* pain during cannulation that radiates distally - indicates thicker vessel wall
* hard to prevent leakage
* colour of blood in chamber is a brighter red
* any decrease in warmth of pulse volume
refer to hospital - leave cannula in for intra-arterial procaine
why does haematoma occur during IV cannulation? how should it be managed?
poor technique
older patient
* decreased collagen in vessel walls
lack of pressure after removal of cannula
* apply for 2-3 minutes
reassure that this will resolve
how should you manage pain during cannulation?
topical anaesthetics
* EMLA
* ametop
minimise with good technique
* distraction
* allow swabs to evaporate
* do not re-use cannula
how should you administer IV midazolam to a patient under 60yo
1mg increments (5mg ampoule) over 30 seconds
wait for start of effects 1-2 minutes
1mg increments at 1-2 minute intervals until adequate sedation
observe patient and assess reaction
flush cannula with saline
how should you administer IV midazolam to a patient over 60yo
2mg/2ml ampoule
0.5mg over 1 minute
pause for 4 minutes
0.5mg increments at 2-3 minute intervals until adequate sedation
often only need 1-2mg
observe patient and assess reaction
flush cannula with saline
how can over-sedation occur?
- failure to observe patient’s behaviour
- too rapid drug administration
results in respiratory depression
management for over-sedation?
- encourage to breathe deeply
- supplementary oxygen
- remove obstruction / reposition head
- administer flumazenil
what is flumazenil? how is it administered?
BDZ antagonist
administered IV or intranasal
* 200 micrograms IV over 15s
* if no change in 1 min, 100 micrograms over 15s
* repeat at 1 min intervals
* maximum 1mg/course
how should a patient be assessed for discharge after IV sedation?
rombergs’ sign
* patient is able to maintain balance with their eyes closed
eve’s sign
* patient able to touch the tip of their nose with their eyes closed
can stand and walk unaided
how does a child’s airway differ from an adults?
- larynx more rostral
- relatively larger tongue
- angled vocal cords
- different shaped epiglottis
- funnel shaped larynx
ess
what are the effects of nitrous oxide?
direct CNS depressant
* lesser extent activates inhibitory reflexes
* alters sensory threshold for touch, temperature, light and sound
* impairs sense of time
peripheral vasodilator
mild sedative, anxiolytic
potent analgesic
weak amensic effect
why is inhalation sedation safe?
nitrous oxide is not metabolised within the body - there are no excretion products
less irritant to bronchial mucosa than other agents
no requirement for fasting
how does diffusion hypoxia occur in IS?
caused by rapid release of N2O from the blood (when insufficient O2)
* insoluble N2O leaves blood stream and displaces the oxygen in the alveoli
* alveolar air normally contains 4% O2, if this is displaced patient feels asphyxia (light headed, disorientated)
management of diffusion hypoxia
administer 100% oxygen for 3-5 minutes
what are the advantages of IS?
- rapid absorption + rapid onset (2-3 mins w peak effect 3-5mins)
- drug level is earily altered or discontinued
- minimal impairment of reflexes
- some analgesia is produced
what are the stages of analgesia when it comes to nitrous oxide?
- plane 1: 5-25% moderate sedation - feels relaxed
- plane 2: 20-55% dissociation sedation - detached from surroundings
- plane 3 - 50-70% total analgesia - approaching GA (unsafe), verbal contact lost
what are some indications for inhalation sedation?
children
* more susceptible to hyponotic suggestion
medical compromised
* diabetes, epilepsy
* cardiac disease ( causes vasodilation - takes stress of heart )
liver/renal impairment
unpleasant dental treatment
needle phobia
* no cannulation
* pain relief + vasodilation
gag reflex
intolerance to other sedatives
* if theres a contraindication to BDZ
what are some general contraindications to IS?
lack of cooperation
* patient needs to understand need to breathe with nose
* limited use with those with learning difficulties
type of dental procedure
* maxillary anterior region
* inadequate seal may lead to gas leakage
what are some medical contraindications to IS?
- blocked nasal airway
- chronic obstructive airway disease
- claustrophobia
- pregnancy - 2nd trimester
- severe learning difficulties
- severe or uncontrolled systemic disease
- myasthenia gravis
- eye/middle ear surgery - increased internal pressure
- vit B12 deficiency - bone marrow suppression
- severe psychiatric disorders - unpredictable response
what are some disadvantages of IS?
- not hugely potent
- clear nasal airway
- restriction of hood into operating field - anterior mouth
- pollution
- intimidating equiptment - associated with GA
- space occupying equipment is difficult to keep in GDP
- chronic staff exposure ; potential for addiction
- lack of operator control
- expensive equipment
what are the side effects of nitrous oxide?
depresses B12 metabolism
* prolonged exposure (>6 hours/week)
* may result in megaloblastic anaemia, neurological damage, bone marrow depression, liver disease
chronic exposure affects reproductive system
* lutenising hormone
nausea & vomiting
* usually psychological
diffusion hypoxia
* although rare
what are the safety features of an IS machine?
minimum O2
* not able to go below 30% oxygen
* high safety margin
O2 fail safe
* N2O flow stops if pressure falls below 40 psi
air entrainment valve
* opens to allow air into circuit if flow rate is too low
oxygen flush button to allow 50L/min O2 in emergency
one way valve on expiratory mask
reservoir bag
* 3L reservoir for patient to breathe from
* allows monitoring
* flow rate adjusted to patient’s minute volume
how is N2O pollution reduced in IS?
active scavenging system
good surgery ventilation / room changes every 12-15hour
short operating times
* minimise conversation w patient - reduce mouth breathing
staff rotation
describe the technique for IS
- consent and hood selection
- O2 at 6L/min
- allow reservoir bag to fill
- place mask
- observe bag throughout
- introduce 10% N2O for 1 min
- if needed add further 10% for 1 min
- after 20% - increase by 5% if needed
- start treatment if sufficient sedation
- at end turn N2O flow off
- administer 100% O2 for 3-5 mins
- sit upright slowly
- discharge after 15 mins
what are the signs of adequate sedation?
- maintain verbal communication
- relaxed
- respiration rate within normal limits
- reduced blink rate, movements and gag reflex
- mouth opens on request
- maintains own airway
- decreased response to painful stimuli
- lethargy
- warmth
- indifference to passage of time
what are the signs of oversedation in IS?
- persistent mouth breathing
- closure of mouth
- unpleasant feelings
- lack of cooperation - uncontrolled laughter
- nausea & vomiting
what are some alternative sedation techniques used for dental anxiety?
- premedication
- intranasal sedation
- transmucosal sedation
- oral sedation
how is premedication used for dental anxiety?
- typically BZD to reduce anxiety 1-2 hours before appointment or the night before
- taken outside of surgery
- do not drive or operate machinery
- unpredictable response
what is intranasal sedation? what are the indications?
midazolam 40mg in 1mL with 20% lidocaine HCL
* quick effect
* can redose
indications:
* patient cannot tolerate cannulation
* patient will still need to be cannulated once sedated
what is transmucosal sedation?
absorption of active agents across the mucosal surfaces
rapid rabsorption
what is oral sedation?
BDZ given - usually midazolam in drink
* 20mg adults, 0.5mg/kg children
* 45min - 1hour preop
* monitor, when sedated can get IV access
* long acting, slow onset
