Nitrous Oxide

Nitrous Oxide

Also called: Laughing Gas

Summary

Nitrous oxide is used during dental treatment to ease anxiety in patients. It is a slightly sweet-smelling gas that is mixed with oxygen and inhaled by patients through a nosepiece or mask. It is often used in addition to a local anesthetic.

Nitrous oxide promotes mental and physical relaxation, as well as a lessened awareness of pain. Patients receiving nitrous oxide remain awake and responsive to a dentist’s requests. These patients may also experience a tingling or floating sensation, warmth, drowsiness, euphoria, the presence of droning background sounds and decreased motor control. Effects last only as long as the gas remains in the body. After the nitrous oxide is turned off, a patient returns to a fully alert state within minutes.

Nitrous oxide is very safe as long as an adequate concentration of oxygen is delivered simultaneously.

This form of sedation may be used for a wide variety of dental treatments. Its use depends on patient preference more than medical need. It may be recommended for patients with mild to moderate dental anxiety, a hypersensitive gag reflex or cardiac problems. Patients with any form of nasal or respiratory obstruction (including a stuffy nose) should not receive nitrous oxide because nasal passages need to be clear for the sedation to work. In addition, nitrous oxide may not be appropriate for patients with certain medical conditions or under certain circumstances.

If patients receive too much nitrous oxide, they may experience nausea, vomiting and dizziness. Increased sleepiness can lead to unconsciousness. Headaches may occur if a patient does not receive adequate oxygen after the nitrous oxide tank has been turned off. Medications that sedate or depress the central nervous system may interfere with nitrous oxide and can lead to a state of unconsciousness. Patients should inform their dentist about all medications and supplements they are taking.

Nitrous oxide is safe for use in patients of all ages, including children. Elderly patients may be more sensitive to the gas and should consult the dentist about whether nitrous oxide is appropriate for them. Women who are pregnant or breastfeeding should inform the dentist about their condition and any concerns they may have about using nitrous oxide. No conclusive evidence is available regarding its safety to fetuses and breastfeeding children. Generally, nitrous oxide is considered a safe, mild sedative with few side effects.

About nitrous oxide

Nitrous oxide is a gas administered in dental offices to reduce anxiety and alleviate pain during dental treatment. It is mixed with oxygen and inhaled by patients through a nosepiece or mask. This type of mild sedation is typically used with an injected local anesthetic that numbs the area to be treated.

Nitrous oxide is provided to a patient just before treatment begins. The gas is inhaled into the lungs, where it enters the bloodstream. From there, it is carried throughout the body, affecting bodily sensations. It is then carried back to the lungs, where it is exhaled, unchanged. Nitrous oxide is not metabolized (chemically broken down and absorbed) in the body. It does not combine with body tissue, which is why the effects of nitrous oxide last only as long as the gas remains in the body.

It is not clear exactly how nitrous oxide works. Nitrous oxide appears to intercept pain impulses before they get to the brain, or alter how they are interpreted. Pain sensations are not completely blocked with nitrous oxide, although patients experience an increased tolerance to pain while receiving the gas.

Patients on nitrous oxide remain awake and responsive to a dentist’s requests. Their autonomic, protective reflexes continue to function, such as the gag reflex and coughing, which help to avoid inhaling foreign material into the lungs. Nitrous oxide may relax a patient’s gag reflex, but does not completely eliminate it. Although patients’ speech may be slurred and motor responses slowed, patients will generally be relaxed and cooperative throughout the procedure.

Nitrous oxide is very safe as long as an adequate concentration of oxygen is delivered at the same time.

Patients breathe in the slightly sweet-smelling gas through hoses on the nosepiece or mask. The hoses connect to two cylinders: one containing nitrous oxide and the other containing oxygen. There is also an additional hose that suctions exhaled gases. The amount of gas released from each of these tanks is controlled to maintain the desired level of sedation. The percentage of nitrous oxide to oxygen in the mixture varies, but may range anywhere from 25 percent to 40 percent nitrous oxide. The average patient requires between 30 percent and 35 percent nitrous oxide.

Administration of nitrous oxide typically involves the following steps:

  • Nosepiece or mask is placed over patient’s nose.

  • Patient receives 100 percent oxygen (no nitrous oxide) for several minutes.

  • Nitrous oxide flow begins, increased in 5 percent to 10 percent increments until desired state of sedation is reached (this usually takes three to five minutes).

  • After treatment is completed, a patient is given 100 percent oxygen (no nitrous oxide) for at least five minutes. This allows the oxygen to flush any remaining gas from the patient’s lungs, leaving the patient alert.  

A record may be kept of a patient’s experience with nitrous oxide. Documentation requirements vary from state to state, but can include the concentrations of nitrous oxide and oxygen used, duration of sedation, length of oxygen recovery at the end of the procedure, and a patient’s response to the gas. 

Most dentists are licensed to administer nitrous oxide. It is a popular anti-anxiety agent for dental treatment for a number of reasons, including:

  • Safe to use
  • Easy to administer
  • Works almost immediately
  • Rapid recovery
  • Requires no special preparation (e.g., not eating for a length of time prior to its use)
  • Requires no special aftercare (e.g., capable of driving a car home)
  • Can be used in patients of all ages
  • Few side effects
  • Patient remains awake and responsive during treatment

Disadvantages of nitrous oxide include difficulty for the dentist in physically maneuvering around the nosepiece or mask during treatment. Nitrous oxide may also be abused by some patients or dental professionals. There has been some concern about the recreational use of nitrous oxide among adolescents. Repeated misuse of nitrous oxide may result in numbing of the hands and legs, neurological problems, kidney or liver problems or other health concerns.

Conditions treated with nitrous oxide

Nitrous oxide can be used to relieve anxiety and lessen pain for almost any type of dental treatment. Its use often depends more on a patient’s preferences than medical need.

The use of nitrous oxide may be recommended for patients with the following conditions:

  • Mild to moderate dental anxiety. Nitrous oxide may lessen a patient’s fear and make dental treatment more tolerable. This can ensure patients receive adequate dental care despite their fear.

  • Hypersensitive gag reflex. Nitrous oxide does not completely eliminate a patient’s gag reflex, but does lessen its sensitivity. This may make dental treatment more comfortable for patients with hypersensitive gag reflexes.

  • Cardiac conditions. Because nitrous oxide is a mild sedative that does not alter a patient’s blood pressure or heart rate, it is a safe form of anxiety and pain relief for patients with cardiac conditions.

Nitrous oxide may also be recommended for patients who do not receive local anesthesia (e.g., due to allergies or refusal of local anesthesia).

Conditions of concern with nitrous oxide

Nitrous oxide is not recommended for patients with any of the following conditions:

  • Nasal obstruction. Nasal passages need to be clear for gases to be appropriately exchanged while receiving nitrous oxide. This allows the patient to achieve a sedated state. Any condition that obstructs the nasal passages (including a stuffy nose) may prevent effective sedation with nitrous oxide.

  • Respiratory conditions. Patients with respiratory conditions (e.g., asthma) may have difficulty inhaling the gas into their lungs. The severity of a patient’s condition may determine whether nitrous oxide can be used, and a dentist should carefully evaluate whether to administer nitrous oxide to these patients.

  • Chronic obstructive-pulmonary disease (e.g., emphysema, bronchitis). Patients with these conditions who receive the nitrous oxide/oxygen gas may end up receiving more oxygen than they normally breathe, which can cause a patient to stop breathing.

  • Previous negative experience with nitrous oxide. Nitrous oxide may not be appropriate for patients who have previously experienced problems using the gas.

  • Special needs. Patients with behavioral problems or certain medical conditions (e.g., mental retardation, multiple sclerosis, epilepsy) may not be able to respond appropriately while under nitrous oxide sedation.

  • Severe dental phobia. Patients with extreme fear of dental treatment may require a higher level of anesthesia instead of sedation with nitrous oxide.

  • Language difficulties. Under nitrous oxide sedation, some patients may experience increased difficulty understanding and responding to the dentist during treatment. This may include people who have a different native language than the dentist or people who stutter or have other communication problems.

  • Contagious diseases. The use of nitrous oxide may not be recommended for patients with contagious diseases because the disease (e.g., tuberculosis) may be transmitted through hoses connected to the nosepiece or mask that cannot be completely sterilized.

Potential side effects of nitrous oxide

Nitrous oxide is used during dental treatment with the intention of easing anxiety in patients. Administration of the gas typically produces pleasant sensations that can help a patient relax. This is the desired level of sedation when using nitrous oxide in a dental setting. The sensations patients may experience with nitrous oxide include:

  • Mental and physical relaxation
  • Indifference to surroundings/time
  • Lessened awareness of pain
  • Tingling in the hands and feet
  • Numbness in hands, feet, thighs, mouth or tongue
  • Feeling of heaviness or lightness
  • Floating sensation
  • Presence of droning sounds (a constant, monotonous tone)
  • Hearing that is distinct, although sounds seem distant
  • Drowsiness
  • Warmth
  • Euphoria (may include dreaming, laughing, giddiness)
  • Dissociation (alteration in a person’s sense of self)
  • Slurred speech
  • Slower-than-normal response time
  • Decreased motor control

Approximately 15 percent of people who receive nitrous oxide experience negative side effects. This may occur due to too high a concentration of nitrous oxide in the gas, or from a sudden change in the amount of nitrous oxide a patient inhales. Negative side effects of nitrous oxide may include:

  • Headaches
  • Nausea, vomiting
  • Excessive sweating or shivering
  • Vertigo (sense of spinning, dizziness)
  • Increased sleepiness
  • Unconsciousness

Patients who experience any discomfort while receiving nitrous oxide should inform the dentist immediately. Headaches may occasionally result when patients do not receive oxygen for at least five minutes after the nitrous oxide has been turned off. This helps to flush any remaining gas from the lungs and return patient to a fully awake and alert condition.

Patients may be advised to keep meals light prior to dental appointments in which nitrous oxide will be used because of the risk of nausea and vomiting. Patients may also be advised to avoid heavy meals for three hours after the appointment.

Some studies have shown that a patient’s motor skills and attention may be affected for 15 minutes after the use of nitrous oxide. Patients may wish to wait this long before driving. If in doubt, patients are advised to ask their dentist whether it is safe for them to drive after receiving nitrous oxide.

Drug or other interactions with nitrous oxide

Patients should inform their dentist about any medications they are taking, including all prescription and over-the-counter drugs, nutritional supplements or herbal medications.

Because nitrous oxide is a sedative, the most significant drug interactions may occur with other medications that sedate or depress the central nervous system (CNS). This includes medications used for anxiety, muscle tension, pain, insomnia and seizure disorders. The combination of CNS depressants and nitrous oxide may lead to a state of unconsciousness.

Symptoms of nitrous oxide overdose

Symptoms of nitrous oxide overdose can be similar to the medication’s side effects, but are usually more severe. Increased sleepiness may indicate hypoxia (lack of oxygen in body tissue) and can lead to unconsciousness. This can occur when a patient receives too high a concentration of nitrous oxide in the gas. To help prevent this, the machines used to dispense the gas are equipped with safety features that may include an audible alarm system or automatic turnoff when the percentage of oxygen in the gas is too low or the oxygen tank is empty.

If a patient reports symptoms of side effects that may indicate overdose, a dentist will most likely turn off the flow of nitrous oxide and allow the patient to breathe pure oxygen through the mask for at least five minutes. This flushes any remaining gas from the patient’s lungs. Any effects of the nitrous oxide should cease after this is done. Also, this will prevent momentary hypoxia as the nitrous oxide exits the blood.

Pregnancy use issues with nitrous oxide

Patients who are pregnant or may be pregnant should tell their dentist about their condition. Conclusive evidence concerning the safety of nitrous oxide in pregnant or breastfeeding women is not available.

Nitrous oxide may be recommended for pregnant women or breastfeeding mothers who need dental treatment because it works quickly, wears off quickly and is not metabolized (broken down and absorbed) in the body. It is a mild sedative and one of the least harmful types of anesthesia.

However, indirect evidence indicates that pregnant women who receive nitrous oxide over longer periods of time have a higher rate of miscarriage or spontaneous abortion than women not exposed to the gas. Some animal studies indicate anesthetics that are inhaled, such as nitrous oxide, can cause birth defects in an unborn fetus. This risk is higher for healthcare providers working in an environment of prolonged exposure to nitrous oxide (e.g., a dental office) than in patients who are only briefly exposed to the gas. Also, women exposed to the gas for more than five hours per week were found to be less fertile than women not exposed to the gas.

Women who are pregnant, breastfeeding, or planning to become pregnant, are encouraged to speak to their dentist about concerns they may have regarding the use of nitrous oxide.

Child use issues with nitrous oxide

Nitrous oxide is safe for use in children. However, not all children are appropriate candidates for nitrous oxide. Children with behavioral problems or certain medical conditions (e.g., mental retardation) may not be able to respond appropriately while under nitrous oxide sedation. Certain sensations (e.g., euphoria) may intensify in these patients, making them difficult to manage. Parents should advise the dentist about any existing conditions or medications their child may be taking.

Nitrous oxide is primarily used in children over 4 years old because it requires cooperation by the patient. A typical demand-valve mask releases nitrous oxide in response to a patient’s inhalation. Younger children may have difficulty breathing normally with this mask, and thus may receive ineffective administration of the gas. Masks with a continuous-delivery feature (that does not require active participation by the child) may be used to administer nitrous oxide to children under age 4.

Elderly use issues with nitrous oxide

Elderly people may be more sensitive to nitrous oxide, which can increase the risk of side effects. Older patients should consult their dentist about whether nitrous oxide is appropriate for them.

Questions for your doctor about nitrous oxide

Preparing questions in advance can help patients to have more meaningful discussions regarding their conditions. Patients may wish to ask their doctor the following questions related to nitrous oxide:

  1. Is it safe for me to use nitrous oxide?
  2. For which dental procedures do you recommend I use nitrous oxide?
  3. How long will the effects of nitrous oxide last?
  4. Can I drive my car after my dental visit?
  5. Are there any risks involved with the use of nitrous oxide?
  6. Do any of my medical conditions indicate I should not receive nitrous oxide?
  7. Will any medications I’m currently taking interfere with nitrous oxide?
  8. How will I feel when I take nitrous oxide?
  9. How will you be able to tell that I have reached an ideal state of sedation?
  10. What types of feelings or sensations may indicate I am receiving too much nitrous oxide (or not enough oxygen)? When should I report this to you?
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