Nitrous oxide (N2O/O2) Sedation
Dayton Children’s
2008
Objectives: Nitrous oxide sedation in pediatrics
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Review the history and evolution
Discuss the physical, chemical, and
pharmacokinetic/pharmacodynamic properties
Explain the regulation/storage
Identify appropriate use of equipment
Review the clinical indications and contraindications
Discuss patient assessment, administration/titration and recovery
Identify potential biohazards for health personnel
History of Nitrous oxide
In 1844, Dr. Gardner Colton
hosted an exhibition to
demonstrate the exhilarating
effects of inhaling N2O. A
volunteer from the audience
began feeling the effects of the
gas and was euphorically
jumping around the stage. He
struck his leg on a bench
causing a deep, bloody
laceration, but he was unaware
of the extent of the injury and denied
feeling any pain.
History of Nitrous oxide
Horace Wells, a dentist in the audience,
was intrigued by the non-responsiveness
to pain. He asked if a tooth could be
removed under the influence of N2O. The
next day, he breathed the gas himself and
had a colleague extract one of his teeth.
He described it as “the greatest discovery
ever made” and “a new era in tooth pulling”.
He continued, with great success, using
N2O on several of his patients who required
tooth extractions and also as anesthesia for
surgeons in the area.
History of Nitrous oxide
• N2O use temporarily diminished with the popularity
of local anesthesia and the discovery of other
anesthetic gases, some more potent. N2O remained
useful in providing rapid induction of the more potent
agents.
• N2O has been most popular in the field of dentistry
but has also been used in emergency medicine,
podiatry, labor and delivery, radiology, and as a
sedation treatment for procedures not requiring
general anesthesia. It has remained in continuous
use longer than any other drug and has an
impeccable safety record.
N2O/O2 sedation
• It is necessary to use oxygen with nitrous
oxide so that the blood remains
appropriately oxygenated.
• A mixture of 20% nitrous oxide and 80%
oxygen has the same analgesic equipotence
as 15 mg of morphine.
General Information-N2O/O2 sedation
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Analgesia -pain control
Anxiolysis -sedative effects
Amnesic – diminishes recall of severity of pain or duration of
procedure
Onset of action – clinical effects begin within 30 seconds, peak
effects within 5 minutes
Titration – very easily allows for the exact amount of the drug
necessary to be delivered to each individual patient
Recovery – rapid and complete. The effects dissipate right away
when the patient stops breathing the gas.
Elimination – 99% eliminated from the body within 5-10 minutes after
discontinuation
Nitrous oxide is the weakest of all inhalation general anesthetics
Physical/Chemical Properties
Physical and chemical properties of N2O
• Nitrous oxide is a sweet smelling, colorless gas
• At room temperature, N2O is a gas. When compressed into a
cylinder, it becomes a liquid.
• The substance itself is not flammable, but will support
combustion. Exposure to a combustible substance or flame
will cause the gas to decompose. If the discomposure occurs
at a high temperature or pressure, an explosion will occur.
• N2O is an oxidizing gas. Therefore, the use of hydrocarbon
compounds, such as lubricants, grease or oil, should be
avoided on any N2O storage, dispensing or distribution
equipment to prevent the risk of fire or explosion.
Physical/Chemical Properties
Physical and chemical properties of Oxygen
• O2 is odorless, colorless, and tasteless.
• O2 is a gas when compressed in cylinders.
• O2 is highly reactive and combines with most elements.
• O2, like N2O, is not itself flammable but supports combustion
when it contacts a combustible material such as oils, grease,
or flammable materials.
• The oxygen molecule does not separate from the nitrogen
molecule in N2O. Therefore, it cannot be considered a source
of oxygen.
Pharmacokinetics of Nitrous Oxide
(uptake, distribution, metabolism, and elimination)
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N2O acts on the body by moving across partial pressure gradients
from a higher to a lower pressure gradient. N2O crosses the alveolar
membrane easily. It is relatively insoluble, meaning it remains
unchanged in the blood and does not combine with any blood
elements. This limits uptake in the body and causes equilibrium to
be achieved quickly. Clinical effects are seen within 3-5 minutes.
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Because of the inability of tissues to hold N2O, it is not stored in the
body to any extent. Elimination is rapid and not impeded.
Pharmacodynamics-Nitrous
oxide interactions with the body
Cardiovascular system
• No negative effects
• No change in blood flow to major organs
• Positive effect on myocardial ischemia by providing
supplemental O2
• Decrease in blood pressure due to relaxation. N2O does not
directly effect the myocardium or voluntary skeletal muscle.
• Decrease in heart rate as anxiety is lowered. N2O has minimal
effect on heart rate.
N2O Interactions with the body
Respiratory System
• Expansive nature of N2O/O2 increases the size of bullae in CF patients, and the
size of a pneumothorax.
• Any condition that compromises air exchange through the nose (URI,
congestion, common colds) may cause insufficient amounts of N2O/O2 to enter
the respiratory system causing incomplete air exchange at the alveolar level and
inadequate sedation.
• The drying effect of N2O/O2 may create mucous plugs in patients with mild URI;
thus, preventing adequate passage of N2O/O2 and inadequate sedation.
• Patients may feel increased sinus pressure as N2O/O2 expands and fills those
air spaces.
• Patients susceptible to hypoxia due to airway resistance, impaired function, or
movement (emphysema, chronic bronchitis) have an increased risk for
respiratory depression and should receive medical consultation before
undergoing any type of sedation.
• Regurgitation and aspiration are a risk if pharyngeal-laryngeal reflexes are lost.
This can be avoided by using the appropriate titration technique so as to avoid
over-sedation and an unconscious state.
N2O Interactions with the body
Central Nervous System (CNS)
• Depresses the CNS
• N2O affects the frequency and voltage
changes on electroencephalograms
(EEGs).
• Increases intracranial pressure in cases
of pneumoencephalography. Do not use
N2O/O2 for 3 weeks following this
procedure.
• Numbness and weakness of extremities
and ataxic gait suggest injury to the
nervous system due to chronic exposure
to N2O.
N2O Interactions with the body
Hematopoietic system
• Megaloblastic bone marrow changes in
patients exposed to high concentrations for
extended periods of time
• N2O is implicated in the interference of the
vitamin B12 dependent enzyme methionine
synthase – necessary for DNA synthesis
and erythrocyte production.
• No negative effects when used for patients
with conditions of red blood cell deficiency,
impairment, and/or destruction as long as
the approved technique is followed which
calls for delivery of supplemental oxygen.
N2O Interactions with the body
Endocrine system
• No negative effects
Hepatic system
• Not metabolized in the liver
• No negative effects
Gastrointestinal system
• N2O diffuses into the air spaces of the peritoneum
and intestines causing increased expansion,
pressure, and discomfort.
N2O Interactions with the body
Genitourinary system
• No negative effects
Reproductive system
• N2O crosses the placental barrier
• Although research confirms the safety of N2O/O2 use with pregnant
women, treatment considerations are important during the first
trimester (when organogenesis occurs) and the last trimester (when
low O2 tension levels are possible).
• Avoid administration during the first trimester.
Neuromuscular system
• Indirectly relaxes skeletal muscle
• Muscle rigidity (secondary to anxiety) with high
concentrations
N2O Interactions with the body
Cancer
• N2O does not combine with any formed blood elements
• Does not affect metastatic cells
• Increases incidence of pulmonary fibrosis and other pulmonary diseases
in patients receiving bleomycin sulfate (used typically for treatment of
lymphomas, testicular tumors, and squamous cell carcinomas).
Allergies
• No reported allergies in more than 160 years
• Use latex free products (rubber nasal hoods have caused contact
dermatitis in latex sensitive patients).
Malignant hyperthermia
• Not considered a trigger for susceptible patients (can be administered
safely).
N2O Interactions with the body
Nutritional disorders
• No effects on any nutritional conditions
Mind-altering conditions
• N2O produces euphoria. Patients/families should be able to
understand the procedure and its effects so the associated signs and
symptoms are not perceived negatively.
• Increased CNS depression with concomitant use of drugs, alcohol,
barbiturates, or sleep aids.
• Be alert for synergistic effects with psychotropic or antidepressant
medications.
• May trigger or exacerbate unwanted episodes from addictions or
mental illness.
• Physical agitation and acts of aggression in severely phobic
individuals.
Regulation and control of Nitrous Oxide
• The N2O industry is regulated by The Food and Drug
Administration (FDA). They set forth and monitor compliance
to both good manufacturing practices and quality system
requirements.
• N2O is considered a hazardous material because of the
pressurization. Its packaging and transport is overseen by The
U.S. Department of Transportation (DOT).
• Sales and security of N2O is regulated by the Compressed
Gas Association (CGA) and the Gases and Welding
Distributors Association (GAWDA).
Regulation and control of Nitrous Oxide
Nitrous oxide Cylinders
• A full N2O cylinder contains
approximately 95% liquid and 5%
vapor
– Liquid N2O in the tank is
vaporized by the ambient room
air temperature outside the
tank as the gas is used
– The tank becomes cool to
touch and frost may be seen
on the tank surface during
prolonged and continuous use.
• Pressure gauge on the cylinder is
not proportional to the actual
amount of gas in the cylinder.
• The gauge will show a pressure
decrease when the tank contains
approximately 20% N2O.
Oxygen cylinders
• A full O2 cylinder contains 100%
gas (vapor)
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The pressure gauge will accurately
reflect the amount of gas present in
the cylinder at all times until it is
empty.
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The N2O/O2 sedation machine is
driven by O2 flow. If the O2 tank
empties, the N2O flow stops and
the sedation is interrupted. It is
important to have extra O2
cylinders available during sedations
to prevent interruption.
Storage of equipment
• Nitrous oxide equipment must be stored in
a secure, locked space which may vary
depending on the unit or department.
• Regulation of use occurs through the
medication pyxis.
Nitrous Oxide equipment
• Equipment should be current, accurate and include a scavenging
system. This ensures minimal occupational exposure for staff.
• Vacuum and ventilation exhaust must be vented to the outside.
• Inspect pressure connections for absence of leaks.
• Inspect the conducting tubing and reservoir bag to the unit if not
already in place.
• Connect the conducting tubing and reservoir bag to the unit if not
already in place.
• Make sure to have replacement equipment and cylinders on hand.
• Disinfect re-usable equipment after each patient use. Any part of the
tubing that is not corrugated can be sterilized but is not necessary.
Surface disinfection is adequate.
Clinical indications of N2O/O2 sedation
Examples of procedures N2O/O2 sedation could potentially be used
for here at Dayton Children’s:
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Burn / wound care
Closed reductions
Abcess drainage
CVL / PICC placements
G-tube changes
Injections – IM / IV / Port access
Lumbar punctures
Minor surgical procedures
NG tube / pH probe placements
Pelvic / perineal exams
Splinting
Sutures
Urethral catheterizations
Venipuncture
Note: N20/O2 sedation is not recommended for procedures longer than one hour.
Contraindications for use of N2O/O2 sedation
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N2O rapidly replaces N2 in air filled spaces in the body causing expansion of those spaces;
therefore, N2O/O2 should not be used in patients with:
– Pneumothorax
– Middle ear occlusion/surgery
– Recent (within 3 weeks) craniotomy/pneumoencephalography
– Increased intracranial pressure
– Intraocular injury/surgery (injected gas may last up to 10 weeks)
– Maxillofacial injuries
– Intestinal obstruction
– Cystic fibrosis
Current upper respiratory tract infection
Chronic obstructive pulmonary diseases
Vitamin B12 deficiency
Psychological impairment
Phobic individuals
Bleomycin therapy
Current psychotropic drug use
Current or recovering drug use/addiction
First trimester of pregnancy
Any facial injury which would prevent use of the mask
Note: Asthma is not a contraindication
Preparation for Nitrous oxide administration
--Staff qualifications
• Persons administering N2O/O2 sedation must complete the
Nitrous oxide competency course according to the Nitrous
oxide policy.
--Emergency equipment
• Emergency equipment must be readily available to include:
– Oxygen
– Positive pressure ventilation system
– Suction
– Advanced airway equipment
– Resuscitation medications
– Automated external defibrillator
Patient Assessment
Patient history
• Abnormalities of the major organ systems
• Previous adverse experience with sedation or analgesia
• Drug allergies
• Current medications and potential drug interactions
• Time and nature of last oral intake
• History of tobacco, alcohol, or substance abuse
• Pain and anxiety
Assessment of patient risk
• Classify the patient’s physical status using the ASA Physical
Status Classification System
Patient assessment
Pre-procedure evaluation
• Vital signs
– Blood pressure, pulse, respiration, oxygen saturation, and
pain score
• Auscultation of the heart and lungs
• Evaluation of the airway
– Previous problems with anesthesia or sedation?
– Sleep problems?
– Chromosomal abnormalities?
– Determination of size and limitations of the head, neck, and
mouth
– Variations in occlusion and teeth
Patient Assessment
Patient preparation
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It is not necessary to fast prior to the administration of nitrous
oxide/oxygen sedation.
When conditions warrant, it is recommended that patients do not eat
fried, fatty, or greasy food just prior to sedation.
A light meal that includes carbohydrates is appropriate if eaten an
hour or so prior to the procedure.
Patient monitoring
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Level of consciousness – patient response to verbal stimulation
Ventilatory function – auscultate and/or observe the frequency and
depth of respirations
Oxygenation – pulse oximetry can uncover early hypoxemia
Administration of N2O/O2
Titration is an important skill in
administering nitrous oxide.
Titration is a method of administering a
drug in incremental amounts until a
desired endpoint is reached. If done
properly, the patient does not receive
more of the drug than is necessary.
For pediatric patients, titration in 10%
intervals is recommended.
Administration of N2O/O2
Advantages of N2O titration
• Only the amount of drug
required by the patient is
given.
• Allows for individual
biovariability
• Uncovers idiosyncratic
reactions early
• Minimizes negative
experiences with over
sedation
Administration of N2O/O2
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Adjusting levels appropriately
A common mistake is to deliver a preset percentage of N2O to a patient. This can result
in either under or over sedation. Most of the negative patient experiences occur
because of over-sedation due to operator error.
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Because of individual biovariability, patients will require different levels of N2O on
different days and for different procedures. the percentage of N2O a patient received at a
previous visit is not relevant to the current appointment.
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N2O can be increased or decreased, depending on the intensity of the procedure. Begin
with 100% O2, then titrate to the desired percentage of N2O. This should generally be
between 20-50%. Levels between 50-70% are considered moderate sedation, and
monitoring parameters must be followed accordingly.
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Patients should be closely monitored. The onset of clinical effects is rapid, and signs and
symptoms of sedation could be missed. Once signs and symptoms of sedation appear,
monitor patient responses and allow time for doses to reach their peak effect.
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As the procedure nears completion, N2O should be discontinued gradually, and replaced
with 100% O2. A minimum of 5 minutes of post oxygenation is required.
Administration of N2O/O2
Fundamental principles for appropriate administration
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Be enthusiastic and confident that the experience will be positive. This
attitude will transfer to the patient.
Be knowledgeable about what N2O can and cannot accomplish.
Informed consent must be obtained prior to administration.
Physician does not have to be present when administering nitrous
oxide.
Do not adopt a fixed dose philosophy. The amount of N2O required by
a patient on any given day or time varies.
The procedure begins and ends with 100% pure oxygen.
Do not leave the patient alone. Constant monitoring must be done by a
professional trained in N2O/O2 sedation.
Document accurately.
Maintain patient in a comfortable position.
Maintain open communication with the patient. The use of guided
imagery is an essential component.
Successful nitrous sedation
Appropriate minimal sedation
• Patient is comfortable and relaxed. (Look for shoulders to drop, legs
uncrossing, arms laying looser, deeper respirations)
• Patient acknowledges reduced fear and anxiety.
• The patient’s mood may be categorized as happy, pleasant, ambivalent
• Patient is aware of surroundings.
• Patient responds to directions and conversation.
• Eyes become less active and glazed look appears.
• Patient may experience:
– Tingling in extremities and/or near mouth
– Heaviness in leg and arms
– Body warmth
– Light feeling
– Vasodilatation in face and neck
– Circumoral numbness
Potential side effects of nitrous oxide
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Detachment / disassociation from environment
Dreaming, hallucinating, or sexual fantasizing
Out-of-body experiences
Floating and/or flying
Physical body movements may become restless, combative, sluggish
Inability to move, communicate, or keep mouth open
– Words may be slurred or repeated; incoherent sentences
Humming or vibrating sounds that progressively worsen
Fits of uncontrolled laughter
Patient may experience:
– Drowsiness
– Dizziness / Light headedness / spinning sensations
– Diaphoresis
– Nausea / vomiting
– Fixed eyes
– Uncomfortable body warmth
– Unconsciousness
Sedation Recovery
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Immediately post procedure, slowly decrease the nitrous, and begin
administration of 100% O2 for a minimum of 5 minutes. This
oxygenation period can be extended until both the patient and
caregiver are satisfied that adequate recovery has been achieved.
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Just as Nitrous oxide provides a rapid onset of sedation, a correlated
rapid emergence from sedation will occur as well. Keep in mind that
each individual is different and recovery times may vary.
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Mental and psychomotor impairment does occur with N2O. The
clinician has the ultimate responsibility to determine if a patient is
completely recovered before their discharge.
Sedation Recovery
Assessing recovery
• The assessment begins after the initial 5 minute post procedure
oxygenation period and before removing the oxygen and nasal
hood.
• Obtain vital signs
• Question the patient about how they feel.
– Any lethargy, headache, dizziness, confusion, nausea?
• If any symptoms are present, continue O2
• Discharge only when assured patient is fully recovered.
– Patient should be alert and oriented with a pleasant demeanor
– Vital signs should be stable and within baseline limits
– Patient responses, eye appearance, and body movement
should be within baseline limits
Documentation
Documentation of the procedure should include the
following:
• ASA classification
• Indications for N2O/O2
• Pre and post Aldrete score
• Pre and post procedure vital signs (including SpO2)
• Concentration of nitrous oxide and duration of administration
• Length of time post procedure oxygen was administered
• Patient recovery
• Adverse reactions / comments
Potential biohazards of N2O for health professionals
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No direct evidence suggests any causal relationship between chronic
low-level exposure to N2O and potential biologic effects.
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The following preventive measures to reduce or eliminate trace gas
contamination are encouraged:
– Operate a delivery system with scavenging capabilities, accurate
flow meter, adequate vacuum, and a variety of mask sizes.
– Maintain a ventilation system to include vent exhaust to outside and
fresh air exchange when possible.
– Maintain an adequate suction system – ensure vacuum of at least
45L/min, use appropriate size mask, discourage patient talking.
– Inspect cylinder attachments, lines, hosing, and reservoir bag for
leaks.
– Calibrate flow meters every 2 years.
Conclusion
• N2O/O2 sedation can reduce the stressful and painful experiences
of our pediatric patients who require minimal sedation. It may be
used in children 2 years and over.
• Please refer to the hospital policy ‘Nitrous Oxide Sedation’ for
specific information about the use of N2O/O2 at Dayton Children’s.
• Clinicians who will be administering N2O/O2 sedation will receive
additional education and complete a competency on the N2O/O2
equipment to be used at Dayton Children’s.
References
Clark, M. & Brunick, A. (2007). Nitrous oxide and oxygen sedation
(3rd ed.). UK: Elsevier.
Farrell, M., Drake, G., Rucker, D., Finkelstein, M. & Zier, J. (2008).
Creation of a registered nurse-administered nitrous oxide program
for radiology and beyond. Pediatric Nursing, 34(1), 29-35.
Retrieved September 23, 2008, from CINAHL Nursing database.