Nitrous oxide sedation in the emergency department

Disclaimer These guidelines have been produced to guide clinical decision making for the medical, nursing and allied health staff of Perth Children’s Hospital. They are not strict protocols, and they do not replace the judgement of a senior clinician. Clinical common-sense should be applied at all times. These clinical guidelines should never be relied on as a substitute for proper assessment with respect to the particular circumstances of each case and the needs of each patient. Clinicians should also consider the local skill level available and their local area policies before following any guideline.  Read the full CAHS clinical disclaimer

Aim

To outline the safe and effective use of inhaled nitrous oxide / oxygen for the management of procedural pain and anxiety in the Emergency Department.

Risk

Failure to follow this guideline may result in sub-optimal and ineffective management of a patient’s pain and anxiety, and potential complications. Refer to contraindications and precautions below.

Key Points

• Nitrous oxide is a Schedule 4 medical gas used to provide amnesia, anxiolysis and analgesia during painful procedures.^1,2
• It has a quick onset (1-2 minutes) and rapid offset (5 minutes) making it an ideal agent for use in short procedures in the Emergency Department.¹
• Nitrous oxide is colourless and odourless.
• Throughout the procedure the child will not be fully asleep. However, memory of the procedure will be suppressed.

Definitions

• Demand or Trigger Flow Nitrous Oxide / Oxygen System:
  • A Trigger Flow System is a mixer which delivers up to a 70:30 nitrous oxide to oxygen mixture (patients should not be given more than 60:40 without ED consultant approval. 50:50 is usually sufficient for most procedures).
  • This is administered via a face mask or a mouthpiece to children aged 12 months and over.⁴
  • The Demand or Trigger Flow System can be used with a mask and is very sensitive to patient respirations making it suitable for young patients or those with difficulty coordinating use of the mouthpiece. 
• Nurse-Led Nitrous Oxide / Oxygen (50:50) Administration:
  • For procedures not requiring medical presence (i.e., urinary catheterisation, port needle insertion).
  • Refer to the staff requirements and procedure below for the administration of nitrous oxide / oxygen without medical staff present.
• Continuous Nitrous Oxide / Oxygen:
  • A continuous nitrous oxide system delivers a continuous flow of nitrous oxide and oxygen without the requirement for the patient to trigger gas flow.
  • Available in the PCH ED dental room for use by the dental team.

Indications

Indications include but are not limited to the following.

• Wound management – including cleaning, suturing, gluing, local anaesthetic injection and dressing.
• Removal of foreign bodies.
• Intravenous (IV) insertion.
• Reduction of fractures and/or dislocations.
• Catheterisation.
• Minor fracture manipulation.

Contraindications

• Head injuries with loss of consciousness (LOC) or altered conscious state.
• Chest injuries or suspicion of pneumothorax.¹
• Trapped gas scenarios (e.g., bowel obstruction, marked abdominal distension, decompression sickness, sinusitis, maxillo-facial injuries).¹
• Acute respiratory conditions (e.g. current exacerbation of asthma, pulmonary oedema, burns to airway, airway obstruction).⁴
• Altered conscious state (e.g., drug intoxication / overdose).⁴
• Cardiac disease.¹
• Note: Staff or family who are pregnant or may be pregnant should not be exposed to nitrous oxide. Pregnant parents or carers should be advised of the risk.

Complications^{3, 4} 

• There is an increased risk of complications when using a concentration greater than 50:50.
• Following administration of greater than 50:50 nitrous oxide to oxygen, 100% oxygen is essential to prevent diffusion hypoxia.
• Drowsiness and over sedation.
• Pallor with nausea / vomiting (up to 10% with 70:30 nitrous oxide to oxygen).
• Excitement / hallucinations / confusion.
• Light headedness / headache.
• Shortness of breath.
• Tingling of fingers / toes.
• Disorders of taste / smell. 

Preparation

Staff Requirements

•   Medical staff must complete the sedation checklist and discuss the case with the senior ED doctor before proceeding with nitrous oxide administration.

Education and Training

• Nursing staff responsible for administering nitrous oxide / oxygen and patient monitoring for medical-led procedures must:
  • Be a Registered Nurse or Enrolled Nurse who has worked in PCH ED for a minimum of three (3) months. 
  • Have completed the Nitrous Oxide Theory Worksheet and the PCH Emergency Department Nitrous Oxide Administration Competency Assessment Tool with a minimum of two successful practical assessments.  
  • Ineligible nurses - All other nurses including agency, casual and relieving nurses in PCH ED are not permitted to administer nitrous oxide or monitor patients receiving nitrous oxide.
• Nursing staff responsible for nurse-led nitrous oxide / oxygen administration and patient monitoring must meet the competency requirements outlined in the Nurse-Led Nitrous Oxide / Oxygen (50:50) Administration section below. 

Prescription

• Nitrous oxide is a Schedule 4 (therapeutic use) medication and must be prescribed prior to use by an authorised prescriber (Medical Officer / Nurse Practitioner) on the WA paediatric Hospital Medication Chart (pHMC).
• The prescription must include the percentage (e.g. nitrous oxide 50% / oxygen 50%), route (inhalation) and duration (0 – 30 minutes).
• Nitrous oxide / oxygen may be administered continuously for up to 30 minutes, then can be repeated after a five-minute break.
• Total daily usage must not exceed one hour per day to prevent megaloblastic bone marrow changes.
• The concurrent use of other sedatives and opioids, particularly by intravenous injection, may lead to significant oversedation or respiratory depression. Use of such drugs should be discussed with an ED Consultant or the Senior Medical Officer (SMO) prior to administration.

Demand Nitrous Oxide / Oxygen Administration

• Minimum of 2 staff⁵:
  • Proceduralist: Doctor, Nurse Practitioner or Registered Nurse (for nurse-led procedures).
  • One credentialled staff member whose sole responsibility is administering nitrous oxide / oxygen, monitoring the patient and documenting their response. If further assistance is required for the procedure, additional staff will be required.

Nurse-Led Nitrous Oxide / Oxygen (50:50) Administration

• Minimum of 2 staff:
  • Proceduralist: Registered Nurse
  • One credentialled staff member whose sole responsibility is administering nitrous oxide / oxygen, observing the patient and documenting their response. If further assistance is required for the procedure, additional staff will be required. 
• The nurse administering the nurse-led nitrous oxide / oxygen (50:50) must be triage competent or above, have completed the required orientation and be assessed by senior nursing staff and deemed competent and confident to deliver sedation.
• Prior to commencing the procedure, a medical order must be obtained and documented on the WA paediatric Hospital Medication Chart (pHMC) as described in the Prescription section. 
• Nurse-led nitrous oxide / oxygen administration must not to be given in combination with opioids. If this is required, medical staff must be present for the procedure.

Continuous Flow Nitrous Oxide / Oxygen Administration

• Minimum of 2 staff: 
  • Proceduralist: Dentist
  • Dedicated nurse for clinical observations. Continuous flow in the dental room will be led by the Dentist.
• For dental procedures using continuous nitrous oxide in the dental room, the shift coordinator and ED Consultant need to be aware that a procedure using continuous nitrous oxide will be undertaken. 
• The continuous nitrous oxide / oxygen unit in the dental room is compatible only with the proprietary nasal hoods for delivery (to allow access to the mouth for dental treatment).

Equipment 

• High flow oxygen and suction must be checked and available prior to commencing the procedure.
• Resuscitation equipment should be checked and present.
• Trigger flow system via a mixer and mask / mouthpiece breathing circuit. Both piped and cylinder nitrous oxide are available in ED. 

Patient Preparation 

Fasting

• Preferably 2 hours prior to the procedure but may be shortened depending on the urgency of the procedure.⁵

Consent

• Verbal or written consent must be obtained from the patient’s parent or carer and documented after a clear explanation of the procedure and the use of nitrous oxide, including the roles of the patient and parent / carer.
• Consent must be documented on the procedural sedation chart, with nitrous oxide / oxygen recorded as the proposed sedation and either continuous flow or demand clearly documented.

Monitoring

• Continuous monitoring of conscious level, respiratory effort, colour and oxygen saturations, +/- cardiac monitoring.⁶
• For Continuous Nitrous Oxide / Oxygen Administration for dental procedures:
  • Monitor pulse oximetry and sedation score throughout the procedure. Document observations 5 minutely during procedure and for 10 minutes post procedure on the Procedural Sedation Record MR301.07.
• For Demand Nitrous Oxide / Oxygen Administration:
  • Document observations 15 minutely during procedure and for 10 minutes post procedure on the Procedural Sedation Record MR301.07.

Procedure

Equipment Setup

• Refer to Appendix 1: Demand Administration Setup Using Piped Nitrous Oxide / Oxygen and O-Two eAdvantage® Equipment (available in Fast Track Treatment Room, Plaster Room, B23B, Resus 1, Resus 2, Resus 3).
• Refer to Appendix 2: Demand Administration Setup Using Portable Nitrous Oxide / Oxygen and O-Two eAdvantage® Equipment.

Administration

Steps: Demand Nitrous Oxide / Oxygen Administration using the O-TwoTM eAdvantage® Equipment

Using a mask or mouthpiece Choose a Mask or Mouthpiece to commence.  Commencing demand procedure: Attach continuous pulse oximetry and record baseline full set of observations. Ensure the procedural sedation checklist is completed including verbal or signed consent. Document verbal or signed consent. Make note and document the child’s weight, fasting status, allergies. Confirm the procedure before proceeding. Start by encouraging with the child to practice with 100% oxygen to gain familiarity with the process.  Set nitrous oxide to the prescribed concentration (commence at 50:50, this may increase to 60:40 if required). A new medical order must be written before administering a higher concentration. If requiring 70:30, contact the ED consultant to discuss suitability.  For Nurse-Led nitrous oxide / oxygen administration, the concentration must not exceed 50:50. Allow child to breathe through mask / mouthpiece. Nitrous oxide is being delivered when the green lung icon is visible on the screen. Nitrous oxide should be administered in blocks of up to a maximum of 30 minutes, as described in the Prescription section. Administration may be repeated following a 5-minute break; however, a new medical order is required. Total daily usage must not exceed 1 hour.7 If over sedation occurs, push and hold the white ‘O2’ enrichment button located above the on/off switch to purge the circuit. See Appendix 3: Oversedation Treatment for reference. Once the procedure is complete, administer 100% oxygen for 2-3 minutes. Following administration of greater than 50:50 nitrous oxide to oxygen, 100% oxygen is essential to prevent diffusion hypoxia. Continue monitoring the child for 10 minutes post procedure.

Post-Procedure

Aftercare

• Turn off any gas flow.
• Discard the whole circuit.
• The patient may be discharged once child returned to pre-procedure mental status and meets all criteria as pre the procedural sedation record MR 301.07.
• Document any adverse reactions or complications on the procedural sedation chart MR 301.07.

References and related external legislation, policies and guidelines

1. UpToDate. Pediatric procedural sedation: Pharmacologic agents. [Updated 20 Feb 2025; Cited 25 May 2026]. Available from: https://www-uptodate-com.pklibresources.health.wa.gov.au/contents/pediatric-procedural-sedation-pharmacologic-agents?search=nitrous%20oxide%20contraindications%20AND%20child&source=search_result&selectedTitle=1%7E137&usage_type=default#H2152505 

2. Li, X. Nitrous Oxide in Pediatric Dentistry: A Meta-Analysis. International Dental Journal. [Internet]. 2025. [Cited 25 May 2026]. Available from: https://doi.org/10.1016/j.identj.2025.104257

3. Great Ormond Street Hospital for Children NHS Trust. Pain relief using Entonox®. 2019. [Cited 25 May 2026]. Available from: Pain relief using Entonox® | Great Ormond Street Hospital

4. Royal Children’s Hospital Clinical Practice Guideline. Nitrous Oxide – oxygen mix. [Cited 25 May 2025]. Available from: Clinical Practice Guidelines : Nitrous Oxide - oxygen mix

5. Australian and New Zealand College of Anaesthetists. Guideline on procedural sedation. PG09(G) Sedation. 2022. [Cited 25 May 2026]. Available from: Professional documents | ANZCA

6. Australian and New Zealand College of Anaesthetists. Guidelines on monitoring during anaesthesia. PG09(G). [Cited 25 May 2026]. Available from: Review P9 (1996)

7. Society for Pediatric Sedation. Procedural sedation guidelines for nitrous oxide administration [Internet]. 2017 May 8. [cited 24 Jun 2026]. Available from: Guidelines for the use of Inhaled Nitrous Oxide (N2O) utilizing the Sedara® Unit

Appendices

Click here to download Appendix 1, 2 and 3. 

Endorsed by:	CAHS Drug and Therapeutics Committee	Date:	Oct 2026
		Review date:	Oct 2028

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