Inhalation sedation I

Question 1

What is conscious sedation? (3)

Answer 1

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.

Question 2

Demand for sedation (4)

Answer 2

Visiting dentist is second most common fear after public speaking (USA 1987)
Child Dental Health Survey 2013
-50% moderately anxious
-10% extremely anxious
‘The control of anxiety and pain is fundamental to the practice of dentistry’ (GDC, 2002)
Deaths at dentist from GA in practice

Question 3

Sedation techniques (6)

Answer 3

Inhalation – nitrous oxide/oxygen, sevoflurane
Intravenous – midazolam, propofol
Transmucosal – midazolam (intranasal, buccal)
Oral – temazepam, diazepam, midazolam, ketamine
Intramuscular - ketamine
Combination of above

Question 4

Nitrous oxide today (3)

Answer 4

Recreational use
‘Hippie crack’ - legal high
Deaths due to hypoxia

Question 5

Properties of of nitrous oxide (5)

Answer 5

Volatile
Denser than air – 1.0:1.5
Least potent - MAC50 is 104
Often used in anaesthesia as carrier/induction gas
Poorly soluble – rapid onset/rapid recovery

Question 6

Pharmacokinetics of nitrous oxide/ oxygen sedation (6)

Answer 6

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 minutes

Question 7

Pharmacodynamics of nitrous oxide/ oxygen sedation (4)

Answer 7

Analgesic
Anaesthetic
Hypnotic
Anxiolytic - GABA

Question 8

Stages of anaesthesia (4)

Answer 8

1) Analgesia
2) Excitement
3) Surgical analgesia
4) Respiratory paralysis

Question 9

Stage 1 of anaesthesia - analgesia (3)

Answer 9

Plane 1
Moderate sedation & analgesia (5-25% N20)

Plane 2
Dissociation sedation and analgesia (20-55% N20)

Plane 3
Total analgesia (50-70% N20)

Question 10

Adequate sedation (8)

Answer 10

Awake
Feels relaxed
Suggestive state
Giggling
Verbal responses
Maintaining mouth open
Reduced blink rate
Spontaneous respiration

Question 11

Over-sedation symptoms (9)

Answer 11

Patient no longer enjoying the effects 
Hysterical laughter, tears
Decreased cooperation
Nausea/vomiting
Mouth closing – repeatedly
Snoring
Incoherent speech
Irrational and sluggish responses
Loss of consciousness

Question 12

Indications for sedation (7)

Answer 12

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

Question 13

Contraindications for sedation (8)

Answer 13

Social
-severe anxiety / claustrophobia / no consent / no escort
-lack of understanding
Medical
-blocked nose / URTI / unable to nose-breathe
-recent eye / middle ear / sinus / intracranial surgery
-bleomycin therapy / Myaesthenia Gravis
pregnancy – 1st and 3rd trimesters
Dental
-traumatic procedures / unsuitable for LA alone
-treatment on upper anterior teeth – lip trapped

Question 14

Safety features/ checks for sedation (4)

Answer 14

1) Pin index
2) Scavenging at 40L/minute
3) Nasal mask and tubing
4) Oxygen failsafe
5) Max 70% N20
6) Oxygen flush
7) Air entertainment valve
8) Reservoir bag

Question 15

N2O / O2 pre-op instructions (5)

Answer 15

Light meal
Take routine medicines as usual
Children must be accompanied to and from their appointment by a competent adult
Do not bring other children
Can cause dizziness/ nausea/ headaches at higher doses

Question 16

Technique

Answer 16

Safety checks, consent, check escort
Introduce to child (giggle gas etc.)
Start O2 and turn up flow rate (5-6L/min)
Fit mask and encourage nose breathing
Titrate N2O - 10% per min to 30% and then 5% per min until sedated
Hypnotic suggestion, clinical monitoring
100% O2 minimum of 3 minutes to recover

Question 17

Record keeping for sedation (8)

Answer 17

Consent and escort
Safety checks completed
Second appropriate person (dental nurse)
Mask size
Flow rate
Max dose
Response/ level of co-operation
Recovery time

Question 18

Reducing exposure in sedation - COSHH exposure limits (4)

Answer 18

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

Question 19

Reducing exposure (4)

Answer 19

Rubber dam
-inconclusive but seems logical
Well fitting mask
Good technique
-reduce mouth breathing / conversation/titrate carefully
Good initial patient assessment

Question 20

Occupational hazards in sedation (7)

Answer 20

Reproductive
Haematological 
Neurological
Also reports
-hepatic disease
-renal disease
-cytotoxicity
-malignancy

Question 21

Reproductive occupational hazards from sedation (3)

Answer 21

Miscarriage
-maternal and paternal influences
-twice as likely to miscarry if scavenging not provided
Reduced fertility in dental assistants working unscavenged offices for over 5 hours per week
Possible risk of teratogenesis

Question 22

Haematological hazards from sedation (4)

Answer 22

N2O oxidises vitamin B12
Inactivates methionine synthase
Impairs DNA synthesis, affecting haematopoesis
Pernicious anaemia

Question 23

Neurological occupational hazards from sedation (3)

Answer 23

Methionine essential for myelin synthesis
Peripheral neuropathy
Spinal cord degeneration/ myelopathy

Question 24

Cumulative effect of occupational hazards from sedation depends upon (4)

Answer 24

Pattern of exposure
Tissue sensitivity
Vitamin B12 intake and stores
Extent to which methionine synthase is deactivated

Question 25

Evidence for N2O/ O2 sedation (3)

Answer 25

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

Question 26

Advantages of inhalation sedation (6)

Answer 26

* Non-invasive technique * Drug level easily altered or discontinued * Minimal impairment of reflexes * Drug administered and excreted through the lungs so no metabolism and thus rapid recovery * No fasting required * Some analgesia

Question 27

Disadvantages of inhalation sedation (9)

Answer 27

* Lack of potency of nitrous oxide * Expense of equipment * Requirement for a clear nasal airway * Intrusion of nasal mask into operating field * Patient perception of equipment * Space occupying equipment * Chronic exposure of staff * Potential for staff addiction * Lack of operator control

Question 28

Suitable patients for inhalation sedation (6)

Answer 28

* Unpleasant treatment * Anxious children/Anxious adults * Needle phobia * Patients who retch easily * People with special needs * Medically compromised patients

Question 29

Contraindications to inhalation sedation (a lot)

Answer 29

* Respiratory tract obstruction * Nasal obstruction * Cyanosis at rest due to chronic cardiac or respiratory disease * Inability to communicate or co-operate (age, severe learning difficulty) * First trimester of pregnancy * Acute fear of the GA mask * Multiple sclerosis * Myasthenia gravis * Claustrophobia * Severe personality disorders * Recent ophthalmic surgery using inter-ocular gases * Any condition where there is air entrapment in the body eg myringoplasty, head injury, pneumothorax, maxillofacial injury etc * Procedures where the mask may interfere with operative work * Current medication check BNF eg methotrexate

Question 30

Problems associated with ASA III patients (4)

Answer 30

* Consultation with medical colleagues advised * Stable but may deteriorate rapidly * Deterioration aggravated by anxiety and stress * Diagnosis of deterioration difficult particularly under sedation

Question 31

Properties of an ideal inhalation sedation agent (9)

Answer 31

* Alleviate fear and anxiety * Produce a degree of amnesia and analgesia * Suppress vomiting reflex, but not protective reflexes * Prolong potential operating time * Be rapidly effective * Be easily eliminated * Have no side effects * Be safely and easily administered by the operator * Require no special precautions or procedures

Question 32

Nitrous oxide systemic effects (10)

Answer 32

* CNS Depression of all senses * CVS Slight depression at high concentrations * RS Non-irritant, slight increase in minute volume * Non allergenic * No significant effect on GIT, liver, kidney * Increases incidence of spontaneous abortion? * Decreases fertility if long exposure? * Inhibits action of methionine synthetase for Vitamin B12 production, can cause impaired bone marrow function. * Thus can affect DNA production and produce pernicious anaemia like effects * Long term exposure leads to peripheral sensory neuropathy

Question 33

Minimum alveolar concentration (5)

Answer 33

* MAC is defined as the minimum alveolar concentration of anaesthetic at 1 atmosphere that produces immobility in 50% of those patients or animals exposed to a noxious stimulus * It is a measure of anaesthetic potency * MAC is reduced in the elderly and by other sedative agents * Nitrous oxide 105% Isoflurane 1.15% Sevoflurane 0.65%

Question 34

Diffusion hypoxia (5)

Answer 34

* Described by Fick 1955 * Seen in the 10 minutes following cessation of inhalation sedation * After administration is terminated, the rapid elimination of nitrous oxide into the lungs dilutes the oxygen within the alveoli and lowers the alveolar oxygen concentration * Responsible for most reports of headache, nausea and lethargy post-operatively * Prevented by routine administration of 100% oxygen for 3-5 minutes post-operatively

Question 35

Reducing occupational exposure (lots)

Answer 35

* Regular servicing of machine and checking by staff * Vent dental suction out of the surgery * Minimise leaks from poorly fitting facemasks * Check flowmeters are not inadvertently left on, * Limit length of appointment * Use low concentrations where possible * Take regular breaks * Use a large room if possible * Adequate room ventilation, open windows, fans at floor level * Active or passive scavenging to remove pollution at source * Encourage the patient not to talk or mouthbreathe * Use rubber dam * N2O monitors * Secure equipment at the end of the day

Question 36

Possible effect of chronic exposure to high levels of nitrous oxide (7)

Answer 36

* Teratogenic effects * Increased rate of spontaneous abortion * Decreased fertility * Increased incidence of hepatic disease/Impairment of renal function * Non specific neurological disease * Bone marrow dysfunction * Anaemia like symptoms

Question 37

Abuse of nitrous oxide (6)

Answer 37

* Used for pleasurable and recreational purposes since 1772 * Main abusers are professionals with easy access to the drug * Always keep a cylinder stock record. 1 nitrous oxide cylinder will be used up for about 2.5 oxygen cylinders * Prolonged exposure toxic to rapidly dividing cells * Peripheral neuropathy, numbness, pain tingling in extremities, that may be irreversible * Although nitrous oxide has been legal in the past, since the Psychoactive Substances Act came into effect on 26 May 2016, it is now illegal to supply or import nitrous oxide for human consumption

Question 38

Safety features - nitrous oxide (lots)

Answer 38

* Used for pleasurable and recreational purposes since 1772 * Main abusers are professionals with easy access to the drug * Always keep a cylinder stock record. 1 nitrous oxide cylinder will be used up for about 2.5 oxygen cylinders * Prolonged exposure toxic to rapidly dividing cells * Peripheral neuropathy, numbness, pain tingling in extremities, that may be irreversible * Although nitrous oxide has been legal in the past, since the Psychoactive Substances Act came into effect on 26 May 2016, it is now illegal to supply or import nitrous oxide for human consumption