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Clinical Practice Guidelines
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Nitrous Oxide

Classification

Inhaled anesthetic

Indications

EMR: Relief from moderate to severe pain

Includes pain caused by extremity injuries, burns, or other injuries or clinical conditions not including inhalation injuries

Contraindications

Traumatic or spontaneous pneumothorax
Air embolism or decompression sickness following a recent SCUBA dive
Bullous emphysema
Gross abdominal distension
Altered mental status or an inability to comply with instructions
Inhalation injury (i.e., smoke or chemicals)
Nitroglycerin use within five minutes prior to administration of nitrous oxide

Consider the use of the mnemonic CDCPAIN:

Ability to Comply
Decompression sickness
Altered level of Consciousness
Pneumothorax
Air embolism
Inhalation injury
Nitroglycerin use within five minutes

Adult dosages

EMR: All indications

Self-administered to effect

Pediatric Considerations And Dosing

Follow weight-based dosing

EMR: All indications

Self-administered to effect

Mechanism Of Action

As used in BCEHS, nitrous oxide is supplied as a 50/50 mixture with oxygen and known as Entonox. Nitrous oxide is a sweet-smelling, colorless gas that is a potent analgesic and a weak anesthetic, whose specific mechanism of action is not well understood. It is believed that endorphin release is likely involved in the analgesic effects of nitrous oxide.

Pharmocokinetics

When administered by inhalation:

Onset: rapid
Peak: immediate
Duration: requires continuous use

Nitrous oxide is excreted unchanged from the body through the lungs.

Adverse Effects

Lightheadedness, dizziness, numbness in lips, sedation, drowsiness, disorientation
Nausea and/or vomiting

Warning And Precautions

Nitrous oxide's blood/gas partition coefficent at body temperature is significantly higher than that of nitrogen's. It will therefore expand into internal gas spaces in the body, and must not be used in cases where additional gas loading would be dangerous (e.g., decompression sickness or air embolisms, abdominal distension, pneumothorax); this phenomenon accounts for the majority of nitrous oxide's contraindications.
Do not use nitrous oxide in confined spaces that cannot be adequately ventilated. When using nitrous oxide inside an ambulance, ensure exhaust fans are running or windows are open to provide for sufficient ventilation of the patient compartment.
Do not use nitrous oxide aboard aircraft due to the risk of flight crew exposure.
Nitrous oxide must be used with caution in patients who are hypotensive or in shock, have ingested or are suffering from the effects of depressant drugs, have a history of chronic obstructive pulmonary disease, or have suffered facial injuries.

Drug Interactions

The depressant effects of nitrous oxide can be potentiated by the presence of other CNS depressants such as alcohol, sedatives, antihistaminics, or psychotropic medications.