2. Medicolegal Issues with Nitrous Oxide Sedation in Pediatric Dentistry
Introduction:
Most of the children attending dental office are cooperative and express a positive attitude toward
dental treatment but some display an unwanted behavior. Children who are very young or with
particular conditions that increase the difficulties of the dentist in providing safe and acceptable
treatment. When a dentist treats a pediatric patient, the first problem of concern is the child’s
behavior (Veerkamp and Wright, 2014). Many nonpharmacological behavior management
techniques can be used to give proper treatment to the children and guide them to have a positive
attitude for the further dental visits. Unlikely, not all children can be managed using these techniques
alone, and pharmacological behavior management such as sedation and general anesthesia are
needed (Webb and Moore, 2002). Due to the associated risk and high cost compared to sedation,
general anesthesia should be avoided (Folayan et al., 2002). Putting patient on sedation to deliver
treatment, when conventional behavior management techniques failed, is preferred (Lourenco-
Matharu et al., 2012).
An efficient method of dropping preoperative anxiety in children and in adult patients who suffer
from anxiety is conscious sedation, especially before surgical procedures requiring general
anesthesia. Conscious sedation has been used to aid in the reduction of patient pain and anxiety when
induced before dental treatments. Conscious sedation is very useful in improving patient cooperation
and rising overall patient satisfaction with dental treatment. In the other hand, conscious sedation
methods have some level of risk for patients and dentists.(Almenrader et al., 2007)
There are different routes of conscious sedation medications administration:
1) Oral: the most commonly used oral agent is Midazolam. It produces fast sedation, amnesia
and improved awakening compared to diazepam. The onset is 60- 90 seconds and its action
for small doses last 10-15 minutes. It is easy to administer and monitor, and it costs less.
3. However, the depth of sedation cannot be easily altered, and there is no analgesic effect
(Anika, 2013).
2) Parenteral administration/ Intravenous sedation The conventional technique is the use of
titrated dose of a single benzodiazepine, opioid, or propofol. The actions can be inverted by
using agents like naloxone. Other routes include intramuscular and subcutaneous
administration. However, they are not commonly practiced (Anika, 2013).
3) Inhalation It is the simplest route of drug administration. The drugs delivered through this
route have a very fast onset and short recovery time. Titration of the gas may easily reverse
their effect or suspend it entirely by administering only oxygen or room air (Bennett, 1980).
Nitrous oxide is the most popular agent used through this route. However, it has an inherent
disadvantage of being the weakest agent available today.
Aim:
This paper was aimed to alert the dentist to significant medicolegal issues regarding the use of
nitrous oxide inhalation sedation in dental practice.
Methods:
Electronic databases search of English scientific papers was done using Pub Med/ Midline and
SCOPUS search engines. The following search keywords were used: Nitrous oxide, sedation,
consent, dentistry, medicolegal, abuse, inhalation sedation.
A total number of 402 papers were reviewed and some references of selected articles. Eight articles
were described the medicolegal issues related to using nitrous oxide inhalation sedation in dental
practice.
Nitrous Oxide/ Oxygen (N2O) Inhalation Sedation
Nitrous oxide is a colorless and odorless gas with a weak, sweet smell. It is a potent analgesic
/anxiolytic agent causing depression of the central nervous system, euphoria and a little effect on the
respiratory system(Paterson and Tahmassebi, 2003). It causes mental and muscular relaxation, drops
4. the fear for future dental treatment and has an analgesic effect. It has excellent results in the dental
record with few adverse effects and has reduced the need for general anesthesia in the anxious
patients (Quarnstrom, 2002).
Nitrous oxide (N2O) inhalation sedation is the safest type of sedation used in dentistry (Quarnstrom,
2002). According to Mittal et.al N2O has been reported to be the 2nd
commonly used sedative agent
in pediatric dental session(Mittal et al., 2014).
A Brief History
Joseph Priestley discovered nitrous oxide in 1776. Nitrous oxide was used as a recreational
medication in the early 1800s. Under the effect of the gas, individuals became happy and euphoric;
hence the other name for nitrous oxide is “laughing gas.” In 1844 Horace Wells decided to test the
aneasthetic potentials of nitrous oxide by asking his colleague to extract his decayed molar. The
procedure was uneventful with Wells screaming that it was “a new era in tooth pulling.” Wells had a
good experience from the analgesic effect of nitrous oxide and reported that he was totally unaware
of the treatment and had a pain free experience. Wells used nitrous oxide with high success on his
patients. He was using 100% nitrous oxide with no oxygen which made his patients unconscious and
hypoxic. Using less than 20% oxygen concentrations of can be fatal. Nitrous oxide was used without
oxygen until 1868 when Paul Bert designed an apparatus that could conduct the combination of 25%
oxygen and 75% nitrous oxide. This apparatus led to the modern delivery system responsible for the
remarkable safety record associated with nitrous oxide/oxygen administration.(MacAfee, 1989)
Objectives of N2O/ O2 inhalation sedation include:(AAPD, 2015b)
1. Decrease or eliminate anxiety.
2. Reduce unneeded movement and unwanted response to dental treatment.
3. Elevate communication and patient cooperation.
4. Increase the pain threshold.
5. Increase patient's acceptance for longer appointments.
5. 6. Help in treating mentally or physically disabled or medically compromised patient.
7. Potentiates the effect of any other sedatives.
Mechanism of Action
Nitrous oxide sedation cause “relative analgesia” - A term cleared by Langa as chemically induced
changes in the psychological state which reduce the fear and pain of dental treatment. Also, it refers
to the use of minimum concentrations of N2O combined with high levels of O2 to produce a sedative
and analgesic effect. It helps in causing a feeling of wellbeing and confidence (a state of euphoria)
for the patients. The patient stay awake and cooperative with all his reflexes maintained also
experiences a pleasant feeling of flying and isolation.(Langa, 1976)
Inhalation and exhalation maintain a barometric equilibrium pressure between the air inside the
lungs and outside during respiration. The amount of gas inhaled inside lungs in normal respiration is
known as tidal volume. The quantity of gas inhaled into the lungs every minute is known as minute
volume. The minute volume of an individual is calculated by multiplying the tidal volume with the
number of respirations per minute.
The respiratory system is divided into:
• Conducting zone: wich contains the trachea, bronchus, and segmental bronchioles, they are
responsible for the gasses transportation. This zone is not responsible for regulating the pressure of
the gasses during respiration.
• A respiratory zone: descending from terminal bronchioles to alveolar ducts, alveolar sacs and
alveoli. The pressure grade of gasses during respiration is regulated by the alveoli present in this
zone. This zone compared to the conducting zone is very small but constitutes the most of the lung
volume known as alveolar ventilation.(Clark and Brunick, 2015)
Before inducing N2O, it is necessary to check the minute volume with O2 to determining the flow
rate of inhalation sedation administration. Induction of N2O causing high partial pressure in the
outside air and low partial pressure in the alveoli. The difference in pressure causing rapid infusion
6. of N2O to the alveoli. From alveoli, the N2O passes the low-pressure capillaries and then reach the
brain acting on the gamma-aminobutyric acid receptors causing an anxiolytic and analgesic
effect.(Emmanouil and Quock, 2007)
Indications of N2O:
N2O inhalation sedation is mostly indicated for the management of dental anxiety, especially in
children and it considered as a part of basic behavior management strategies (AAPD, 2015a). A
review done by Paterson and Tahmassebi have proposed the use of inhalation sedation for
management of various conditions like hypoplastic teeth to decrease there sensitivity. Patients with
kidney or liver disease can be treated with N2O because it does not metabolize in the body, sickle
cell disease and severe asthma where high oxygen pressure is mandatory. Also, cerebral palsy
patients can be treated using N2O to control athetoid and dyskinetic activities, cardiovascular disease
as it reduces anxiety, raises the pain threshold and affords increased levels of oxygen(Paterson and
Tahmassebi, 2003).
Asthma: Since that many contra verses regarding using N2O for patient with this medical condition,
Nitrous oxide is distinguished from other agents in that it does not reduce net ventilation.(Eger,
1985) Since N2O is not irritating to the tracheobronchial system, asthma is not a contraindication to
the use of N2O, if the patient is not having an attack. In fact, there is an advantage to administering
N2O because in many asthmatic patients, the primary precipitant appears to be stressed, especially in
children. However, no dental procedure should be done if the patient is having respiratory difficulty
due to asthma.
According to American Academy of Pediatric Dentistry, the indications of using N2O are (AAPD,
2015b):
1) Fearful, anxious, or uncontrollable patient
2) Patients having special health care needs
7. 3) Patients with gag reflex affects dental work
4) Patients cannot obtained local anesthesia
5) A cooperative child undergoing a long dental procedure.
Contraindications of N2O
As with any medication, there are both relative and absolute contraindications for using N2O.
These include patients with respiratory diseases such as chronic obstructive pulmonary disease
(COPD) and asthma, nasal obstruction, and many other conditions.
COPD: Patients with chronic obstructive pulmonary disease have both a decreased ability to move
gasses in and out of the lungs because of reversible bronchospasm and irreversible bronchial
obstruction. Hypoxemia and hypercarbia caused by chronic hypoventilation or poor gas exchange
across the respiratory membranes. Some papers suggest that nitrous oxide should be avoided in
patients who have severe chronic obstructive pulmonary disease.
Nasal obstruction: The inability to use a nasal mask is an absolute contraindication to the use of
nitrous oxide(Becker and Rosenberg, 2008). In general, such patients categorised into (1) those who
cannot inhale properly through the nose because of anatomic and/or disease causing nasopharyngeal
obstructions, and (2) those that cannot tolerate and withstand placement of the nasal mask because of
psychological or cognitive instabilities. Like patients who are severely phobic, cognitively impaired
and pediatric patients. Other examples include patients with a deviated nasal septum, nasal polyps,
upper respiratory tract infection, rhinitis due to allergy, and severe sinusitis. Also, any compromise in
patency of the Eustachian tube may lead to pressure increases within the middle ear, as previously
mentioned. In fact, it has been recommended that any recent surgery of the ear presents a
contraindication for nitrous oxide.(Munson, 1993) Any nasal obstruction will severely restrict the
patient’s ability to breathe through the nose. Patients who are “mouth breathers,” either due to nasal
8. restriction or because of a habit, do not inhale well attempting to breathe through the nasal mask and
often cannot exchange easily through the nose to be comfortable.
Pregnancy: Nitrous oxide freely enters fetal circulation, and because of the possible toxicity of N2O
to cells undergoing mitosis, pregnant patients, especially in the first trimester of pregnancy, should
avoid nitrous oxide electively. However, in a dental emergency, if it is determined that N2 O is
needed to reduce stress; it may be used after consultation with the obstetrician. (Collins, 2015)
Psychiatric patients: they may present sedated due to their usually prescribed drugs. It is best to
consult the patient’s psychiatrist before administering N2O. Although nitrous oxide has been used
successfully in patients with diagnosed personality and psychiatric disorders, it should be utilized
carefully when those diagnosed with schizophrenia or bipolar disorder. These patients are treated
with many psychotropic agents, and the use of nitrous oxide may further alter their temper, leading to
unpredictable action.(Becker and Rosenberg, 2008)
Inability to communicate: since many of the patient monitoring with N2O conscious sedation is
done verbally, inability to communicate with the patient stated as a contraindication to the use of
N2O. These conditions include severely mentally challenged patients, very young patients, language
barriers, or any condition that prevents the easy exchange of thoughts between doctor and patient.
Hallucinogenic drugs: The use of drugs such as marijuana is a contraindication of using N2O
(Bryson and Frost, 2011). Marijuana can enhance an already pleasant situation, and conversely,
increase the dysphoria of an existing stressful situation. Following heavy use of marijuana, the drug
may remain in the circulation for seven or more days due to its very long half-life.
Intracranial pressure: Nitrous oxide has been shown to increase intracranial pressure in patients
with certain injuries and intracranial disorders(Santra and Das, 2009).
9. Highly apprehensive patients: Since N2 O is a relatively weak agent, it should not be used alone in
an apprehensive patient, or as a substitute for anesthesia.(Levering and Welie, 2011)
Blockages: Because N2O has a solubility coefficient that is 35 times higher than nitrogen, it can
quickly displace nitrogen in any closed cavity, and increasing the pressure within rapidly. Thus,
conditions such as blocked Eustachian tubes, blocked bowel, acute blocked sinusitis and
pneumothorax that cause a rapid increase in pressure in a closed body cavity, leading to pain counted
as a contraindicate of using N2O.(Yagiela, 1991)
Depression of bone marrow activity: N2O exposure may cause a depression of bone marrow
activity, resulting in a decrease in the production of erythrocytes and leukocytes. However, since
normal marrow contains a “store” of mature cells adequate to supply several days’ needs, and the
marrow improves to return to production within 3 to 4 days, no hematologic change is seen after an
isolated anesthetic or conscious sedation exposure to nitrous oxide. However, another exposure
within this period will prolong inhibition of synthesis, which may exceed the safety factor of stored
cells. Since chronic exposures at close intervals may produce leukopenia, frequent exposure to
nitrous oxide should be avoided (Weimann, 2003).
According to American Academy of Pediatric Dentistry, there several contraindications of using
N2O (AAPD, 2015b):
1) Chronic obstructive pulmonary disease.
2) Severe emotional disturbances or patients depending on drugs
3) 1st
trimester of pregnancy.
4) Patients treated with bleomycin sulfate (an anti-neoplastic antibiotic, which is known to cause
pulmonary toxicity)
5) Cobalamin deficiency and methylenetetrahydrofolate reduction
10. Adverse Effects
In children, complications associated with the use of inhalational sedation are of more importance
because of their small body size, decreased oxygen reserve, higher basal oxygen consumption, and
lower residual lung capacity compared to adults. The potential complications of inhalation sedation
are summarized on Table 1.
Table 1: The potential complications of inhalation sedation(Malamed, 2010)
Adverse Effect Description Management/ Prevention
Diffusion hypoxia If nitrous oxide administration is discontinued
and the absorbed nitrous oxide diffuses out of
the blood and into the alveolar spaces.
Administration of 100%
oxygen ( washout) for 5
minutes upon termination
using N2O.
Nausea and vomiting The most common adverse effect of inhalation
sedation
Causes:
A) The presence of food in the stomach:
Heavy meals before using inhalation sedation
can easily cause nausea and vomiting, mainly
in pediatric patients. However, patients
receiving treatment on an empty stomach are
also more vulnerable to nausea and vomiting. It
is recommended to have a high-carbohydrate
meal 4 to 6 hours before the appointment.
B) Oversedation
A reliable and consistent sign of over-sedation
1. Turn off N2O, and let the
patient continue breathing
100% oxygen.
2. Remove the nasal hood from
the patient's face.
3. Remove the rubber dam and
any other intraoral dental
material.
4. Turn the patient's head and
body to the side away from the
dentist side. This aid the
vomitus to pool in the cheek
11. is a response from the patient that he or she
feels bad, "sick to the stomach," usually
proceeded by sweating and pallor. The patient
gets over sedated no matter the percentage of
nitrous oxide.
C) The "Roller Coaster Ride."
The ability to titrate can be used to a
disadvantage by increasing and decreasing the
nitrous oxide - oxygen flows, can precipitate
nausea and vomiting.
D) Prolonged sedation time:
The longer the patient receiving sedation, the
greater is the chance of nausea and vomiting.
instead of getting aspirated by
the patient. A volume suction
tip may be used in removing
the vomitus. A dry 4x4 piece
of gauze can aid in removing
vomitus.
5. Following the incident,
replace the nasal hood on the
patient's nose so that the
patient may be permitted to
breathe 100% oxygen for at
least 3- 5 minutes.
6. If the patient does not wish
to continue with nitrous oxide-
oxygen during treatment, it is
best to adhere to their wishes.
If necessary.
7. Antiemetics may be
prescribed preoperatively for
this patient.
Tooth pain associated
with sinus pressure
Nitrous oxide can displace air from the
maxillary sinus. This is because the anterior,
middle and posterior alveolar nerves pass
through the sinus membrane and are affected
by N2O
Decrease the time of sedation
12. Vertigo Prolonged exposure of the vestibule-cochlear
complex to N2O can result on vertigo. This can
cause high tension on the tympanic membrane
which may lead to a change in hearing acuity.
Decrease the time of sedation
Bowel discomfort N2O can displace air spaces in the gut. This
can have an enlargement to the extent that there
are discomfort and flatulence.
Decrease the time and
concentration of sedation
Delivery System of N2O
Mixtures of N2O and oxygen have been used in dentistry for more than 100 years. The usual
analgesia equipment used by dentists contains a N2O and O2 delivery system, a gas mixing bag, and
a nasal mask with a positive pressure relief valve. Analgesia machines for dentistry are stetted to
deliver up to 70 % (700,000 ppm) N2O to a patient during dental procedure. The machine prevents
higher concentrations of N2O from being delivered to protect the patient from hypoxia.
There are two types of nitrous oxide/oxygen delivery systems, Fixed and portable. The fixed
system requires a central system with source of supply of N2 O andO2 located in a storage area
isolated from the treatment rooms. Flowmeters and the accessory apparatus required for the delivery
of the gases exist in in the treatment rooms. The portable unit has a self-contained delivery system.
Mobility is the main advantage of this unit. It is usually the system of choice in dental offices
because of space limitation. The portable unit typically includes a manifold with safety pressure
relief valves, regulators for each cylinder, an alarm monitor gauge, an N2 O and O2 supply source
(cylinders), tank restraints, numerous hoses and gas lines. In the portable system, the manifold, the
N2 O and O2 gas cylinders, and the flowmeter act as one unit. The whole unit resides in the
treatment room. Located on the portable unit, the manifold is a primary component of the nitrous
13. oxide system. Two or four N2 O and O2 gas cylinders may be attached to the manifold, but only one
line for each gas exits the manifold (Austin, 2013).
Scavenging Systems
Scavenging masks are available in different sizes. Efforts should be made to guarantee that the
mask is always well fitted comfortably to the patient. The scavenging system should be connected
and turned on before the nitrous oxide is open. Cleaning of any filter in a receiving system should be
done at least once a week. All scavenging pumps should drain via an appropriately labelled and
constructed terminal, to the outside of the building, away from fresh air intakes, windows, doors, or
walkways (Dillow, 2005).
Deferent types of
delivery systems of
nitrous oxide/oxygen
Scavenging nasal hood system (Malamed, 2010)
14. Nitrous Oxide Induction Techniques:
To administer nitrous oxide to children, there are two ways. The first way is standard titration
technique (slow induction technique). Nitrous oxide started at 10% concentration and increased in by
5 -10% until clinical signs of optimal sedation are reached. The second way of nitrous oxide delivery
is the rapid induction technique. This technique is indicated for mild to moderate anxious patients
and involves administering 50% nitrous oxide directly to the patient without any titration
steps.(Wilson and Ganzberg, 2013).
Administrations Technique of N2O:
It is necessary to have a co-operative, understanding and relaxed patient. The method of
inhalation sedation strongly relies on the dentist’s participation, relaxation of the patient acceptance
and the depth of sedation is enhanced if, with calm, monotonous voice is used. Continued
communication with the patient is necessary. Pre- and postoperative instructions should be given
before treatment to both the patient and escort and consent should be signed for each episode of
sedation and treatment. Following manufacturer guidelines on daily and preoperative equipment
checks is important. On the day of the appointment, the pressure of gauges in the cylinders should be
verified. The gas cylinder valves should be fully opened and checked for leakages. The reservoir bag
should be monitored by obstructing the tubing while both gaseous valves (nitrous oxide and oxygen)
are open and then squeezing the bag and checking for positive pressure against the obstructed tubing.
Finally, the safety mechanism should be checked by turning off the oxygen cylinder while both
gasses are flowing and make sure the nitrous oxide also cuts off.
The way of nitrous oxide/ oxygen inhalation sedation delivery described by The American Academy
of Pediatric Dentistry as follow:
1) Selection of proper fitted nasal hood should be done.
15. 2) A flow rate of 5-6 L/min is adequate to most patients. The dentist continues to reassure the
patient verbally throughout the procedure. After observation of the reservoir bag, the flow
rate can be modified.
3) Introduction of 100 % oxygen for 1-2 minutes followed by titration of nitrous oxide of 10%
intervals. The concentration of 50 % nitrous oxide should not exceed. Regular patient
requires from 30 – 40% nitrous oxide to achieve ideal sedation (Malamed and Clark, 2003).
4) Patient assessment and baseline monitoring should be monitored during the procedure. This
includes monitoring the patient verbal responses, the color of the skin, heart rate and number
and quality of respirations. The signs and symptoms of ideal N2O sedation are reported on
Tabel 2.
5) Nitrous oxide concentration may be lowered during simple procedures, like restorations and
elevated during more stimulating ones, such as, extraction, injection of local anesthetic.
6) To have a smooth and safe recovery phase, the patient breath 100% oxygen for
approximately 3 minutes before removing the nasal hood.
7) The patient should sit in the dental chair for a further 5 minutes before leaving with an
appropriate escort and issued with written and verbal post-operative instructions.(Paterson
and Tahmassebi, 2003, AAPD, 2015b)
16. Table 2: The signs and symptoms of ideal N2O sedation (Malamed, 2010)
Note: not all patient will express all same signs and symptoms
Interaction with Other Medication:
It is well known that N2O have a positive safety effect in children when used at a concentration of
30-40%. The risk of N2O increased when combination with other sedative medication given by
another route (oral or nasal). This resulting on synergistic effect and the risk for CNS depression
increased, causing deeper sedation than needed or expected where reflexes are decreased or lost.
(Levering and Welie, 2011)
Exposer Limits
The Occupational Safety and Health Administration (OSHA) do not currently regulate exposure
limits of nitrous oxide.
The National Institute for Occupational Safety and Health (NIOSH) has reported the
recommended exposure limit (REL) for nitrous oxide of for dental personnel is 25 parts per million
Symptoms Signs
Lightness
Tingling and numbness of hands and feet
Feeling of warmth throughout the body
Numbness of the soft tissues of the oral cavity
Feeling of euphoria
Feeling of lightness or of heaviness of the
extremities.
Elevated heart rate and blood pressure early at
the procedure, then return to baseline.
Normal and smooth respiration
Vasodilatation of the peripheral
Decrease on the anxiety and muscle tone.
Flushing of face and extremities.
17. (ppm) in 8 hours' time-weighted average (TWA) (NIOSH, 1977). The American Conference of
Governmental Industrial Hygienists recommended limiting N2O to 50 ppm (Dunning et al., 1996).
Studies by Dunning et al. reported that the level of exposure by the dentists were significantly
higher than the recommended. N2O level was ranged from 97 - 59 pp. the exposure level for dentist
were significantly higher than dental assistants. A study by Badger and Robertson reported that the
concentration of nitrous oxide in a dental clinic during pediatric procedures and N2O sedation with
scavenging increases in the room air with uncooperative children (222 ppm) compared with
cooperative child patients (124 ppm)(Badger and Robertson, 1982)
Measurement of Nitrous Oxide Exposure
Nitrous oxide exposure can be measured by the utilization of Landauer passive nitrous oxide
dosimeters that are placed as lapel badges during the work day. After a specific period, the capsule is
sealed and sent back to the manufacturer. Investigation is performed on a time-weighted basis. The
results are stated the amount of nitrous oxide exposures in parts per million(Donaldson and
Meechan, 1995).
Potential Effects of Chronic Exposure to Dental Personnel:
It is well known that chronic exposure of dental personnel to low levels of N2O can cause
chronic health effects; however, the risk has not been calculated exactly. The most common effects
of N2O are hematological disorders (Spence, 1987) and reproductive complications both in males
and females (Rowland et al., 1995). It is described that N2O can interfere with Vitamin B12
synthesis, which may result in reduced red blood cell production and development of pernicious
anemia in staff who exposed to N2O for a prolonged time (Spence, 1987). The rate of spontaneous
abortion has been reported to be increased in female dentists, dental nurses and in the wives of male
dentists who have been exposed to N2O for more than 8 hours per week (Rowland et al., 1995)
Nitrous oxide has also been shown to lessen fertility in both males and females. Most of these side
18. effects can be managed through appropriate precautions such as adequate scavenging and good
equipment maintenance. Other adverse effects of chronic exposure to nitrous oxide include:
neurological defects, immunological problems (decreased leukocyte count, decreased leukocyte
motility and chemotaxis), liver problems, renal problems, malignancy, miscellaneous cytotoxicity
(Donaldson and Meechan, 1995, Brodsky et al., 1981)
Acute Exposure and Toxicity:
Acute exposure to nitrous oxide manifested by symptoms such as cyanosis, hypotension,
methemoglobinaemia and manifestations similar to subacute degeneration of the spinal cord. Acute
exposure of nitrous oxide occurs by a lack of oxygen running through the participant's bloodstream.
Nitrous oxide displaced oxygen out of the blood and during acute toxicity the body organs begin to
function irregularly. This can cause irreversible brain damage or death. Acute toxicity by nitrous is
extremely difficult to recognize because it leaves no evidence of its presence (Reynolds et al., 1982,
Cheng et al., 2013).
Medicolegal Issues
Abuse of Nitrous Oxide:
Dentistry is a stressful specialty, and people who practice it are at high risk of divorce, depression,
alcoholism and suicide. Many factors increase this risks including inherent stress, isolation of the
practitioner, physical and emotional demand, prescription writing and easy accessibility to drugs
(Mandel, 1993). Today, N2O abuse is counted as a serious occupational hazard in the dental
community (Blanton, 2006). Recent data suggest that alcohol, is the most commonly abused
substance among dentists (37%), then opioids (31%) while N2O was reported to be 5% of abused
substance (Fung and Lange, 2011). There has been few research on the forms of use and harms
experienced by users of N2O beyond a few case series, often within the health-care profession, of
abuse and dependence (Winek et al., 1995).
19. In 2016 Garakani et al did a systematic review report the common sequelae occurred with
abusing nitrous oxide, these sequelae include:
Neurologic Sequelae:
The most common presentation of neurologic problems includes: myeloneuropathy, peripheral
neuropathy or polyneuropathy, and myelopathy. Patients commonly complained of hallucinations ,
numbness, paresthesia, finally weakness. Thus maybe because of the substance deactivates vitamin
B12, which can cause numbness and difficulty in moving arms and legs. Many patients also
presented with changes in gait or coordination. The least neurological signs and symptoms include
changes in mentation, bowel and bladder and sexual dysfunction.
Medical Sequelae:
Emphysema (dyspnea at rest, wheezing, and chest pain), pulmonary toxicity, acute respiratory
distress syndrome with pneumothorax and cardiopulmonary arrest are the most common signs and
symptoms. Nitrous oxide is very cold when released as a gas from a pressurized cylinder; that may
cause frostbite upon contacting the skin or throat.
Death:
N2O was assumed to be the primary cause of death in many reports. Most of the cases involved use
of a mask or plastic bag and connected to N2O tank directly. N2O was reported in the blood
circulation on post-mortem toxicology, with the N2O being identified by gas chromatography. The
reported causes of death included sudden cardiac arrhythmia or, most commonly, acute asphyxiation
due to hypoxia. Autopsy findings included visceral congestion and pulmonary edema.(Garakani et
al., 2016)
There are several difficulties and challenges related to the detection and evaluation of sequelae
related to N2O abuse. As all substances of abuse, it can be difficult to measure truly and accurately
the degree of N2O abuse. Patients may forget about their amount and duration of use or may lie or
20. deny their recreational N2O use entirely. Detection of N2O in screening tests is difficult, due to its
short half-life and rapid elimination through the lungs (Sandoval, 1993).
Scavenging System
According to Gillman in 2006, he reported that it is illegal and unethical to use N2O/ O2 sedation
without scavenging system. This attitude is criminal and denied the 1993Occupational and Safety
Act, the 1995 Hazardous Chemical Substance Regulation (HCS), the 1987 Environmental
Regulation for the Workplace, since the chronic pollution with N2O has the potential to poison the
exposed people, including the dentist and dental assistants if used without adequate scavenging.
Many health problems related to N2O exposure could be easily eliminated by adequate scavenging
system. Scavenging is mandatory to avoid the possibility of fines and/ or prison (Gillman, 2006).
Consent Form and Documentation:
Respect for autonomy of the pediatric patient in dental clinic is no different from that of the adult
patient, except that the patient is officially incapable of granting consent. Since consent is an
essential condition for treatment, no treatment can be given unless informed consent acquired from
the parent and documented in the patient’s file before administration of nitrous oxide/oxygen. The
practitioner should deliver instructions to the parent regarding pre-treatment dietary restriction if
indicated. The patient’s file should describe the indication for the use of nitrous oxide/oxygen
inhalation, nitrous oxide amount (i.e., percent nitrous oxide/oxygen and/or flow rate), duration of the
treatment, and post-treatment washout procedure. Documentation is critical in protecting the dentist
in the case of a lawsuit (AAPD, 2015b). Sample of consent forms in Arabic and English are provided
at the end of this review.
21. Conclusion:
Nitrous oxide/oxygen must be delivered only by licensed individuals, or under the direct
supervision thereof. The physician responsible for the treatment of the patient and/or the delivery of
analgesic/anxiolytic agents must be skilled in the use of such agents and techniques and proper
emergency management. N2O plays a significant role in managing patients in dental practice.
However many medicolegal issues are missed by the dentist.
First: N2O abuse is well known problem regarding dentists and health care provider. Awareness is
needed to prevent the adverse effect appeared due to N2O abuse.
Second: consent form before starting treatment is crucial. No treatment using inhalation sedation
without consent. The consent should explain on details the indications, the benefits, the side effects
and the dietary restrictions if needed.
22. Nitrous Oxide Consent Form
The purpose of this consent is to provide an opportunity for parents/ guardians to understand and
give authorization for the use of Nitrous Oxide when provided during dental treatment.
1. I accept and understand that Nitrous Oxide is commonly used sedative gas in pediatric dentistry
clinic and offers relaxation, reduced anxiety, and discomfort, although my kid will be awake, fully
conscious, aware of surroundings, and able to respond rationally to directions.
2. I accept and understand that there are alternatives to Nitrous Oxide such as: local anesthesia alone
or combined with oral anti-anxiety drugs.
3. The use of Nitrous Oxide may have side effects while being administered, such as tingling of the
hands and feet, a lightweight or floating sensation, nausea and vomiting, but unusual. All of these
complications are temporary.
4. I have had the opportunity to discuss Nitrous Oxide in conjunction with my kid's dentist, and have
had the ability to ask questions. I am fully satisfied and ready to proceed in light of the answers I
received.
5. I know that my kid should be fasting 4-6 hours before the Nitrous Oxide appointment.
6. I have informed the dentist of my kid's complete medical history including any recent surgeries or
changes in medical history involving lung, respiratory, ear infection or common cold.
7. I have informed the dentist if my kid has sensitivity to any medication.
8. I have informed the dentist about my kid present mental and physical condition.
9. I have informed the dentist of my child past and current medications.
I agree on the use of nitrous oxide inhalation sedation during dental treatment of my child.
Patient Name____________________________ Date__________________
Guardian Signature ___________________ Relation to the Patient ______________
Dentist's Name _________________ Signature ______________ Date ___________
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