Nitrous Oxide Review

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Nitrous Oxide Review

• Dr. Patrick D. McCarty, DDS

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Nitrous Oxide is both an analgesic and an
anxiolytic
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Why Nitrous Oxide?FEAR of an unpleasant
experience, namely PAIN. Nitrous oxide
relieves both the physiological and the
psychological aspects of pain.
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A Brief History of Nitrous Oxide-Nitrous oxide
was used in the early 1900s but deaths occurred
because of faulty equipment -With the
introduction of safe equipment in 1960s it has
regained popularity -65 of general dentists
and almost 90 of pediatric dentists use nitrous
oxide in their offices -Nitrous oxide is still
used today as a party drug
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Rationale for Inhalation Sedation

• The use of inhalation sedation with nitrous oxide
  (N2O) and oxygen (O2) has many significant
  advantages over other methods of pharmacosedation

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Even in the presence of more potent agents,
nitrous oxide is an excellent adjunct due to its
low lipid solubility and as a result excellent
ability to titrate
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Advantages of Inhalation Sedation (N2O O2)

• Onset of Action
• The onset of action of inhalation sedation is
  more rapid than that of oral, rectal and
  intramuscular (IM) sedation. IV sedation onset is
  roughly equal to inhalation.

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Advantages of Inhalation Sedation(N2O O2)

• 2) Peak Clinical Effect
• Peak clinical actions do not develop for
  most oral, rectal and IM drugs for a period of
  time that makes titration absolutely impossible.

Only inhalation and IV drug administration
provide peak clinical action in a time frame
permitting titration.
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Advantages of Inhalation Sedation(N2O O2)

• 3.) Alteration of Depth of Sedation
• The depth of sedation achieved with
  inhalation sedation may be altered from moment to
  moment. With no other sedation technique does the
  administrator have as much control over the
  clinical action of a drug.

This degree of control represents a significant
safety feature of inhalational sedation
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Advantages of Inhalation Sedation(N2O O2)

• 4) Duration of Action
• Duration of action is an important
  consideration in selection of sedation technique.

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Advantages of Inhalation Sedation(N2O O2)

• 5) Recovery Time
• Recovery time from inhalation sedation is
  rapid and is the most complete of any technique.

N2O is not metabolized by the body, the gas is
rapidly and virtually completely eliminated form
the body within 3 to 5 minutes. In all other
techniques the recovery form sedation is
considerably slower.
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Advantages of Inhalation Sedation

• 6) Ability to Titrate
• Titration is the ability to administer small
  incremental doses of a drug until desired
  clinical action is obtained. Ability to titrate
  represents the greatest safety feature a
  technique can possess.

Significant drug overdose will not develop in
techniques in which titration is possible, as
long as the practitioner titrates the drug used.
Intravenous Inhalation Sedation allow for
titration. No other sedation technique is capable
of titration.
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Advantages of Inhalation Sedation(N2O O2)

• 7) Discharge
• In the outpatient setting it is in
  everyones best interest that the patient is
  discharged from the office with no prohibitions
  on their activities.

Drugs administered for the reduction of fear
anxiety are CNS depressants. A patient must have
an escort for a number of hours following
administration of these drugs.
Inhalation sedation recovery is almost always
complete, a patient usually may be discharged
from the office alone, with no restriction on
activity.
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Advantages of Inhalation Sedation(N2O O2)
(cont.)

• 8) No injection required
• 9) Safe, very few side effects
• 10) N2O-O2 has no adverse effects on the liver,
  kidneys, brain, or cardiovascular respiratory
  system.

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Disadvantages of Inhalation Sedation (N2O O2)

• Initial cost of equipment
• Continuing cost of the gases (O2 and N2O)
• Equipment required for inhalation sedation can be
  cumbersome in a dental surgery suite
• Nitrous oxide is not a potent agent. There will
  be a of patients who do not obtain a desired
  clinical effect.
• Patient cooperation is required. A patient must
  be able to inhale the gas through the nose and/or
  mouth. If a patient is unwilling, failure will
  occur.
• There is a possibility that chronic exposure to
  trace amounts of N2O is deleterious to the health
  of dental personnel.

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• Disadvantages
• Mask interferes with treatment
• Will not work on everyone (compliance)
• Equipment and training required
• Possible health risk to staff
• Possible risk of side effects
• Potential abuse by dental health care workers

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• Side Effects
• Amnesia/lightheadedness
• Headache
• Nausea/vomiting
• Insomnia/nightmares
• Most side effects related to diffusion hypoxia.
• caused by inadequate post oxygenation

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• Indications
• The mildly apprehensive patient
• The frightened child
• The gagging patient
• Long procedures
• Low pain threshold
• Adjunct to other sedation techniques

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• Contraindications
• 35 times more soluble in blood than nitrogen, N2
• so fills and expands any air-containing cavities
  
• air embolism
• pneumothorax
• intracranial air
• lung cysts
• intraocular air bubbles
• tympanoplasty
• endotracheal tube cuff (monitor and reduce
  pressure periodically)

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• Nitrous Oxide, N2O ("Lauging Gas")
• Physical Properties
• colorless
• odorless
• nonflammable but, like O2, supports combustion
• gas in room temp and ambient pressure liquid
  under pressure

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• Cardiovascular Effects
• direct myocardial depressant effect balanced by
  sympathetic nervous system stimulation
• so BP and P stable
• myocardial depression may be unmasked by
• CAD
• Hypovolemia
• pulmonary vasoconstriction -gt increased PVR ,
  therefore may exacerbate pulmonary HTN

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• It is safe to use on people with History of
• -Athrosclerosis
• -Arteriosclerosis
• -Rheumatic fever
• -Heart Murmur
• -Angina
• -MI
• -Heart Sx
• - HTN

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• Respiratory Effects
• Tachypnea decreased VT
• BEWARE inhibits carotid body hypoxic drive
• URI
• Occlude nasal passages and inhibit adequate
  ventilation
• Drying effect may lead to mucous plugs
• Sinusitis may be exacerabated due to expansive
  properties of the gas. Resulting in pain and
  discomfort.
• Avoid nitrous sedation until the URI resolves

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• Nitrous Oxide and pts with COPD
• Use with caution.
• Higher apneic threshold.
• These pts rely on hypoxic drive, thus they may
  lose the stimulus for respiration.
• Obtain a physician clearance, recommendation
  prior to administration of Nitrous.

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• Nitrous Oxide and pts with Pneumonia/Emphysema
• May be complicated by nitrous.
• Expansive nature of the gas may increase size of
  an air bulla up to 300 within 10 minutes.
• Avoid nitrous in these patients

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Silent Regurgitation Aspiration

• Pharyngeal Laryngeal Reflexes
• Dye Studies
• 5 to 10 minute sedation resulted in no
  aspiration with nitrous levels of 20 65 in 25
  pediatric patients
• 30 minute sedations revealed 2 aspirations in 10
  pediatric patients
• REINFORCES THE RECOMMENDATION OF NPO STATUS

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• GI System
• Avoid in patients with history of bowel
  obstruction.
• Expansion of bowels.
• Middle Ear Disturbances
• Infiltrates the non-compliant area of the middle
  ear
• Can result in
• Hearing loss
• Graft disruption
• Tympanic membrane rupture

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Complications/Precautions

• Other possible contraindications
• severe cardiac disease
• hyperthyroidism
• uncontrolled diabetes
• sickle cell anemia
• severe asthmatic conditions

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• Biotransformation and Toxicity
• Eliminated by exhalation.
• .004 metabolized in gut bacteria.
• Irreversibly oxidizes cobalt atom of vitamin B12,
  inhibiting B12-dependent enzymes
• methionine synthetase (myelin formation and
  erythrocyte production)
• thymidylate synthetase (DNA synthesis)
• Prolonged exposure can lead to
• bone marrow depression (megaloblastic anemia)
• peripheral neuropathy
• pernicious anemia
• Controversial
• teratogenic usually avoided in early pregnancy

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• Routes of Administration
• N2O is administered via nasal inhalation in an
  open system.
• The patient can terminate N2O effects or vary the
  dose by breathing through the mouth.
• In a closed system (general anesthesia), both
  mouth and nose are covered so patient has no
  control on flow.

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• Administration Rules
• Never use less than 30 oxygen.
• Provide 6-8 liters (.1L/kg) of gas per minute for
  adult, less for child.
• Continually monitor patient.

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• Pre-induction
• Patient should not eat or drink to prevent nausea
  and vomiting.
• Have someone drive them the first time.
• Obtain written consent the first time.
• Put patient in slightly reclined position.
• Establish rapport.
• Check equipment.
• Use standard monitors BP, ECG, SpO2.

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• Administration of N20-02
• Begin with 100 oxygen for 1 minute, flows of
  0.08-0.1 L/Kg.
• Also use reservoir bag to set flows and assess
  seal.
• Add N2O slowly until desired effect is reached
• -add 1 L every 30-60 sec. while maintaining same
  total flow.
• You may adjust level of sedation to intensity of
  procedure.
• Discontinue N2O near end of procedure.
• Post procedure Admin. 100 Oxygen for at least 5
  minutes.
• Have patient rise slowly, assess gait and mental
  status.
• Never discharge patient until return to baseline
  vital signs.
• Post-op vitals /- 10mmHg BP, /-10 HR, /-3RR,
  /-1 SpO2
• If lethargy, dizziness noted, continue 100
  Oxygen for another 5 minutes. Continue to
  monitor.

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• Signs and Symptoms of Sedation
• 1) sense of relaxation
• 2) reduced sense of fear and anxiety
• 3) glazed eyes
• 4) tingling in fingers, toes, cheeks, lips,
  tongue
• 5) heaviness in legs and arms
• 6) hyper-nasal voice
• 7) cheeks may flush

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• Signs of Oversedation
• 1) Giddiness and laughter
• 2) Dissociation form surrounding
• 3) Extreme drowsiness leading to periods of sleep
• 4) Sluggishness
• 5) Stage II- excitement and irritability followed
  by labored breathing and difficulty in chest
  excursions.
• 6) Roller coaster breathing
• 7) unresponsiveness

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Four Stages of Anesthesia

• Analgesia
• patient is conscious
• reflexes are intact
• Delerium
• Surgical Anesthesia
• Respiratory Paralysis

The patient is unconscious in Stages 2, 3, and 4.
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Four Plateaus of Analgesia

• Parathesthesia - tingling of hands, feet
• Vasomotor - warm sensations
• Drift - euphoria, pupils centrally fixed,
  sensation of floating
• Dream - eyes closed but will open in response to
  questions, difficulty in speaking, jaw sags open

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N2O Should Be Used To

• Ease fears and anxieties
• Aid in the treatment of special patients
• Increase tolerance for longer appointments
• Raise the pain reaction threshold

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N2O Should Not Be Used To

• Control defiant or uncontrolled behavior
• Control pain by replacing local anesthesia
• Replace poor techniques of behavior management

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Analgesia

• In analgesia stage, the patient is conscious, has
  all vital reflexes intact, can communicate and
  cooperate with the dentist, and quickly returns
  to a normal state following a few minutes of
  oxygenation.

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Signs of Saturation

• Reminding child continuously to hold mouth open
• No response to questions
• Agitation
• Sweating
• Nausea
• Unconsciousness

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Reduce N2O Dosage...

• with lengthy administration (gt 30 min.).
• Maintenance _at_ 20 40

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Prep for N2O Utilization

• Portable oxygen tank
• Delivery system that delivers a maximum of 80
  N2O (MAC of N2O is 104 )
• Medical history
• Physical evaluation ("...vital signs such as
  pulse, blood pressure, respirations, temperature
  and weight..."
• Oral pharyngeal airways available
• Emergency drugs

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Elimination of N2O

• Rapid
• Primarily through the lungs
• Small amount through skin, sweat glands, urine,
  and intestinal gas

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Diffusion Hypoxia

• High outpouring of N2O
• Dilutes available oxygen in lungs

Ventilate the patient for 3 to 5 minutes to
prevent diffusion hypoxia!
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Effects on Systems

• CNS - primary system effected by N2O
• Respiratory
• respiratory rate increase
• decrease tidal volume
• N2O potentiates respiratory depression with
  concommitant use of narcotics, barbiturates, or
  other sedatives

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Effects on Systems

• Cardiovascular
• normally, no meaningful changes in heart rate or
  pressure
• myocardial depression with cardiac decompensation
  (congestive heart failure)
• patients with ischemic heart disease without
  decompensation may benefit from N2O

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Effects on Systems

• Cardiovascular
• normally, no meaningful changes in heart rate or
  pressure
• myocardial depression with cardiac decompensation
  (congestive heart failure)
• patients with ischemic heart disease without
  decompensation may benefit from N2O

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Chronic Exposure to N2O
Long-term (chronic) exposure to nitrous oxide in
sufficient concentrations can produce
irreversible, toxic changes, and should be a
concern for dental personnel working in
environments in which nitrous oxide is
administered to patients.
Howard, JADA, March 1997
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Chronic Exposure Disorders

• Reproductive
• Hematologic
• Immunological
• Neurological
• Liver
• Kidney

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Safe Concentrations of N2O

• OSHA - not established
• NIOSH - recommended exposure limit (REL) 25ppm
  during administrations
• ACGIH (American Conference of Governmental
  Industrial Hygienists) 50 ppm threshold limit
  value (TLV) over 8 hour TWA (time weighted
  average)

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Safe Concentrations of N2O

• ADA - has not proposed a permissible exposure
  limit, but emphasizes the routine use of
  scavenging equipment

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N2O Scavenging

• Developed out of a concern regarding possible
  health consequences and psychomotor influences
• ADA states that scavenging equipment should be
• used to reduce ambient N2O
• effective regardless of heating and air
  conditioning system in use
• able to achieve N2O standards recommended by
  NIOSH and OSHA

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N2O Scavenging System
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Controlling N2O in the Operatory

• Ventilation
• Fresh air inlets - ceiling
• Return air vents - floor level
• Location of ventilation system exhaust
• Air exchange rate (gt10/hr)

Howard, JADA, March 1997
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Controlling N2O in the Operatory

• Work Practices
• Inspect equipment every day
• Use scavenging system
• Instruct patient to refrain from mouth breathing
  and talking
• Bag should collapse and expand as the patient
  breathes
• After administration, flush the system 100 O2.

Howard, JADA, March 1997