Pain and Anxiety Seminars:
Nitrous Oxide and Oxygen (N2O-O2) Inhalation Sedation
General Information
 Conscious sedation
 Most commonly used inhalation anesthetic agent in dentistry
 Discovered by Joseph Priestly in 1772
Properties
 Non-irritating, sweet smelling, colorless, liquid under pressure (30%), requires heat
for vaporization, relatively insoluble in blood (0.47 is the blood/gas solubility
coefficient), not flammable, not explosive, not biotransformed in body.
Indications
 Anxiety, gagging, pain relief, for dental procedures where local anesthetic would be
more than needed, for lengthy procedures in a medically compromised patient
Contraindications
 Absolute contraindications: Inability to use a nasal mask
 Relative contraindications
o Compulsive personality (“take charge”)
o Claustrophobic person (nasal cannula)
o Children or adults with severe behavior problems
o URI, COPD
o Pregnancy (2nd trimester is better, need consult)
o Psychiatric disorders
Advantages
 Rapid onset (2 – 3”, oral 30”, IM 10 – 15”)
 Rapid peak effect (3 – 5”, oral 60”, IM 30”)
 Titratable, rapid recovery
 Recovery almost always complete
 Safe, non-invasive
Disadvantages
 Cost of equipment
 Not a potent agent
 Patient must be cooperative
 Chronic exposure complication
Armamentarium
 Demand flow units: Not recommended
 Continuous-flow units
o Basic components
 Compressed gas cylinders
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 Reducing valves (regulators)
 Pressure gauges
 Flowmeters
 Reservoir bag
 Conducting tubing
 Full face mask, nasal hood, nasal cannula
Portable (E tank) vs. central storage system (G or H tank)
Scavenging system
Safety Features
 Color code: Blue cylinder (N2O); Green cylinder (O2 – United States); White (O2 –
International)
 Pin indexing system, Diameter – indexed safety system
 Minimal oxygen flow settings: System must deliver at least 30% oxygen (2.5 lpm –
3.0lpm)
 If oxygen runs out, the system shuts down
 Alarm (central storage system)
Technique of Administration
 Begin and end with 100% O2 for at least 3 – 5 minutes
 Begin 6 l/min oxygen (500 ml x 12)
 Titration
o Start 20% N2O and increase 10% every 60 seconds
o Subsequent appointments also should be titrated and not to use the same
concentrations of N2O at each visit
Common Signs and Symptoms
 Light-headedness, dizziness: feeling is transient, increased N2O concentration, not
adequate for Tx
 Tingling sensation of arms, legs or oral cavity: can be done some procedures
(scaling, starting IV, local anesthesia)
 Feeling of warmth, floating, or heaviness: near or ideal level of sedation for Tx
depends on clinician
 oversedation: Nausea (vomiting, unconsciousness)
Because the clinical signs and symptoms are so variable from patient to patient, simply
tell them they will feel more relaxed and comfortable.
Discharge the Patient (Discharge Criteria)
It is important to remember that most of patients will recover adequately enough to
permit their discharge from the office without an escort, but not all patients.
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Vital signs
o BP:  10 mm Hg
o HR:  10 to 15 beats
o Respiration:  3-5 breaths
Motor coordination – Trieger test
Complications
 Excessive perspiration
 Expectoration
 Behavioral problems
 Shivering
 Nausea and vomiting
Chronic Exposure
 Spontaneous abortion, congenital malformation, kidney and liver damage, peripheral
neuropathies
Elimination of Nitrous Oxide from Air
 Stop leaks, ventilation, scavenging nasal hoods
 Minimize talking to patient
 Monitoring of air (above 50ppm, repaired)
Recreational Abuse of Nitrous Oxide
Sexual Phenomena and Nitrous Oxide
 An assistant present in room
 Do not routinely use N2O concentration greater than 50%