Nitrous oxide, a laughing gas for anesthesia

Nitrous oxide, laughing gas

Nitrous oxide

Nitrous oxide, commonly known as laughing gas or nitrous, is a chemical compound, an oxide of nitrogen with the formula N2O. At room temperature, it is a colourless non-flammable gas, with a slight metallic scent and taste. At elevated temperatures, nitrous oxide is a powerful oxidizer similar to molecular oxygen. It is soluble in water.

Nitrous oxide has significant medical uses, especially in surgery and dentistry, for its anaesthetic and pain reducing effects. Its name “laughing gas”, coined by Humphry Davy, is due to the euphoric effects upon inhaling it, a property that has led to its recreational use as a dissociative anaesthetic. It is on the World Health Organization’s List of Essential Medicines, the most effective and safe medicines needed in a health system. It also is used as an oxidizer in rocket propellants, and in motor racing to increase the power output of engines.


Nitrous oxide produces a light anesthesia on its own that’s frequently added to an IV anesthetic or another inhalational anesthetic (e.g. halothane). It can reduce the dose requirement for other drugs. In the case of dental procedures, it may only be added to a local anesthetic. The substance is not very potent. It has a minimum alveolar concentration (M AC) of 105%, making it a poor drug for general anesthesia. It’s instead used at sub-MAC concentrations for conscious sedation or as an adjunct.

Typically the concentration is 30-70%. It’s recommended the concentration be titrated so that an ideal level of anesthesia is provided without raising the chance of negative effects. A review of patient records from the University Of Southern California School Of Dentistry found the typical patient needed 30-40% nitrous oxide.

When used for conscious sedation, the drug helps to reduce pain

, can reduce anxiety, and often offers some level of amnesia (more common as the concentration increases). Anxiolytic itself can be quite useful, such as in pediatric settings. Its low solubility in blood gives it a rapid onset and rapid clearance, with the effects ending shortly after administration ceases. Medical personnel can acutely control what state the patient is in.


Nitrous oxide typically offers stable respiration and circulation, is easily breathed, provides some pain relief, is an anxiolytic, has a relatively low cost, and features an amnestic quality.

Usually there’s little effect on cardiovascular activity. One report showed an hour of 60% N2O in healthy volunteers increased heart rate, stroke volume, cardiac output, and blood pressure. Other reports have shown the reverse, possibly from dual cardiovascular-relevant pharmacological actions.

Another report indicated 30% N2O led to a suppression of sympathetic cardiac activity.
Its analgesic, anxiolytic, and amnestic effects can be useful. Some pain may still be felt in certain settings, but it’ll be reduced and less distressing.


Some of the downsides are that it can inactivate B12, it’s inadequate on its own for general anesthesia, and there are some pressure/volume changes.
It may raise the risk of arrhythmia when combined with halothane. Otherwise the risk appears to be lower in nitrous oxide anesthesia vs. halothane anesthesia.

There appears to be a small increase in cerebral blood flow and volume, leading to a mild rise in intracranial pressure. Some reports have failed to demonstrate this and it may primarily occur in connection with coadministered drugs. For example, this effect appears to exist more when certain amounts of sevoflurane are also used.

Nitrous oxide might increase cerebral metabolic activity in a regional manner.
Its analgesia is useful during procedures, but it doesn’t last into the postoperative period.
There can also be gas pressure and volume changes in some areas of the body, potentially contraindicating its use depending on the situation.

Pre-hospital setting

Sometimes N2O is used before someone reaches a hospital to manage traumatic pain, such as in acute myocardial infarction. In some areas it is given when opioids aren’t available.
This use has become somewhat common in the UK and Canada.


Nitrous oxide has been used in labor for well over a century. Although epidural analgesia appears more effective, N2O is often adequate.
The gas offers analgesia and anxiolysis while preserving consciousness.
It’s a useful option since if the patient dislikes the effect; they can easy discontinue it and switch to something else. Women also maintain greater freedom of movement during labor, which can enhance comfortability.

A 2012 Cochrane review indicated there are analgesic effects and there don’t seem to be adverse neonatal effects.
It is recommended inhalation begins 30 seconds before the start of a contraction.
More studies should be done on its safety and efficacy.

Stanislav Klikovich (Poland) reported this use in 1881 with an 80% N2O/20% oxygen mixture. Equipment for self-administration was introduced by Robert Minnitt in England in 1934.

What are potential short-term side effects? 

Even though side effects can occur from inhaling nitrous oxide, many who receive the gas don’t have adverse reactions or complications at all. When side effects do happen, they often occur as the result of inhaling too much of the gas or inhaling the gas too fast.

Common short-term side effects include:

  • excessive sweating
  • shivering
  • nausea
  • vomiting
  • dizziness
  • fatigue
  • fever
  • chills
  • hives
  • wheezing
  • difficulty breathing

Get immediate medical help if you have any signs or symptoms of an allergic reaction


  • You might not be able to receive nitrous oxide if:
  • You’re in the first trimester of pregnancy.
  • You have a history of respiratory illness or chronic obstructive pulmonary disease (COPD).
  • You have methylene tetrahydro folate reductase deficiency. ·        
  • You have a cobalamin (vitamin B-12) deficiency.     
  • You have a history of mental health conditions.        
  • You have a history of substance use disorders.

While there are no known long-term side effects, misusing nitrous oxide or long-term exposure to the gas in a work environment may cause long-term complications.

Toxic exposure may lead to a vitamin B-12 deficiency or anemia. A severe vitamin B-12 deficiency can cause nerve damage, resulting in tingling or numbness in your fingers, toes, and limbs.

What are symptoms of a nitrous oxide overdose?

Despite the gas being safe and used medically, there’s the risk of overdose. This can occur due to long-term exposure or from receiving too much of the gas.

Signs of a possible overdose may include:
· irritation of the nose, eyes, and throat · wheezing, coughing, or difficulty breathing · choking or tightness in the chest · seizures · bluish fingers, toes, and lips ·  rapid heart rate · psychosis or hallucinations

An increase in blood pressure may also occur. This can raise the risk of a stroke or heart attack.


Brain damage is also a possibility when a person receives a large dose of nitrous oxide without sufficient oxygen. If left untreated, an overdose can cause coma or death.

It’s important to note that overdose effects require an amount many times greater than what you would receive at your dentist’s office.



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