Inhaled anesthetic

Brand Names

Entonox®, Nitralgin®, Nitronox®

EMR: Self-administered relief from moderate to severe pain

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

• 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

Inhaled:

• Onset: less than one minute following 4-5 deep breaths
• Peak: immediate
• Duration: requires continuous use

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

• 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.
• Nitrous oxide is excreted unaltered in the patient's breath.  Administration must take place in a well-ventilated area to prevent others from inhaling the gas. 
• 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. 

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