Management of Entonox
Version
6
Name of responsible (ratifying) committee
Formulary and Medicines Group
Date ratified
19th September 2014
Document Manager (job title)
Libby Burton Smith Acute Pain Sister
Date issued
10th October 2014
Review date
09th October 2016
Electronic location
Clinical Policies
Related Procedural Documents
See section 8
Key Words (to aid with searching)
Entonox; analgesia; procedural pain; rapid onset/offset
Version Tracking
Version
Date Ratified
Brief Summary of Changes
Author
6
19/09/2014
Nil change to clinical content
New Trust template
Libby Burton
Smith
Entonoxf Policy : Issue Number 6 Issue Date 10/10/2014
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CONTENTS
QUICK REFERENCE GUIDE....................................................................................................... 3
1. INTRODUCTION.......................................................................................................................... 4
2. PURPOSE ................................................................................................................................... 4
3. SCOPE ........................................................................................................................................ 4
4. DEFINITIONS .............................................................................................................................. 4
5. DUTIES AND RESPONSIBILITIES .............................................................................................. 4
6. PROCESS ................................................................................................................................... 4
7. TRAINING REQUIREMENTS ...................................................................................................... 6
8. REFERENCES AND ASSOCIATED DOCUMENTATION ............................................................ 6
9. EQUALITY IMPACT STATEMENT .............................................................................................. 7
10. MONITORING COMPLIANCE WITH PROCEDURAL DOCUMENTS .......................................... 8
MONITORING............................................................................................................................ 10
Specific Paediatric Preparation: ........................................................................................................ 13
During the Procedure ........................................................................................................................ 13
Following the Procedure ................................................................................................................... 14
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QUICK REFERENCE GUIDE
Entonox is a ready-to-use medical gas mixture consisting of 50% nitrous oxide and 50% oxygen.
It is a safe and effective analgesic for all situations where rapid onset and offset is sought.
It provides pain relief and conscious sedation in midwifery and for a variety of short term procedures.
Departments carrying out procedures using entonox should be aware of and follow this policy.
All staff involved in administering entonox should have undergone formal training in its use and
handling and be able to recognize and manage any complications.
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1. INTRODUCTION
Many procedures or interventions are painful to the patient and the level of discomfort
experienced is often underestimated or discounted as being part of a therapeutic or beneficial
intervention.
Entonox is an inhaled agent that provides effective analgesia that can be self-administered to
provide immediate pain relief. It is particularly suited for the relief of acute pain as a result of,
for example, injury, trauma, therapeutic investigative procedures and maternity. Entonox was
introduced commercially in 1965 and, following acceptance by the Central Midwives Board,
became the normal method of pain control in childbirth utilised by the midwifery staff. Soon,
Entonox was being used to control pain for accidents and emergencies and, by the early
1970s, was standard issue in most ambulances.
2. PURPOSE
This policy is to guide staff in the use of Entonox. It is not designed to restrict or limit
professional judgment and decision-making
3. SCOPE
This policy applies to all permanent, locum, agency and bank of Portsmouth Hospitals NHS
Trust, the MDHU (Portsmouth) and Carillion, whilst acknowledging that for staff other than
those directly employed by the Trust the appropriate line management or chain of command
will be taken into account.
4. DEFINITIONS
Entonox is a homogeneous gas mixture containing 50% nitrous oxide (N2O) and 50% oxygen
(O2). It is stored in cylinders at 137 bar. This pressurised mixture remains gaseous at
temperatures above –6oC.
Nitrous oxide is a colourless, sweet smelling gas with powerful analgesic properties.
Pulmonary transfer of nitrous oxide is rapid, with onset of effect in seconds and full analgesia
within one to two minutes. Likewise it is rapidly eliminated from the blood, via the lungs, when
inhalation ceases.
Entonox combines the analgesic effect of the nitrous oxide with the anti-hypoxic effect of 50%
oxygen.
5. DUTIES AND RESPONSIBILITIES
Anaesthetists: when an anaesthetist is involved in a patient’s care, it is his/her responsibility
(not that of a surgeon) to seek consent for anaesthesia, having discussed the benefits and
risks.
Midwives: in the maternity setting it is the midwife’s responsibility to establish the use of
Entonox in childbirth, where its use is covered by NICE guidance ‘Care of women and their
babies during labour’ Clinical Guideline 55.
Supervisors of clinical practice: will be responsible for auditing compliance with the BOC
management guidelines on an ongoing basis
6. PROCESS
6.1 Storage
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Where cylinders are brought into the building directly from outside storage during periods
of low external temperature, to ensure gases are properly mixed, cylinders should first be
either
a. Stored horizontally for 24 hours at a temperature above 10oC, or
b. Stored for at least 2 hours at a temperature above 10oC, then completely inverted
three times, or
c. Placed in warm water at body temperature for 5 minutes, then completely inverted
three times.
6.2
Prescribing and administration
Entonox must be prescribed by medical staff or non-medical prescribers with responsibility
for the care of the patient prior to use and should only be administered by staff who are
trained in both its use and the equipment available for its administration.
Entonox is self-administered using a dedicated Entonox demand valve
6.3
Indications
Entonox is indicated for the relief of acute moderate to severe pain of any aetiology (see
contraindications at section 6.3 for exclusion criteria). The pain or discomfort could be: as
the result of injury; due to a procedure carried out in hospital; or that incurred by women in
childbirth and labour. For example:
















Fracture manipulation
Endoscopy (e.g. colonoscopy)
Suturing of lacerations
Venopuncture
Ophthalmic surgery
Vascular procedures
Radiological procedures
Dermatological procedures
Wound dressing changes
Burns dressing
Orthopaedic joint manipulation
Patient mobilisation
Childbirth
Perineal suturing
Wound drain removal
Examination of wounds or fractures
6.3 Contraindications
Contra indication
Rationale
Pneumothorax,
Bowel obstruction
Air embolism
Decompression sickness or following
a recent underwater dive
Following air encephalography
The nitrous oxide constituent of Entonox passes into
all gas-containing spaces in the body faster than
nitrogen passes out. This can cause expansion of the
gas space, compressing surrounding structures.
Severe bullous emphysema
During myringoplasty
Head
injuries
with
consciousness.
impaired
Entonox will cause sedation, which may confound
neurological observation of the patient.
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Drug or alcohol Intoxication
Maxillo-facial injuries
Heavily sedated patients
Drowsiness and aspiration would be a hazard in the
event of vomiting.
The patient may not be able to hold the mask tightly to
the face or use the mouthpiece adequately.
The patient may be unable to use the equipment
properly and increased sedation may be hazardous.
See Appendix 1 for protocols for practice. Critical Incident reporting within the Anaesthetic
Department and completion of Trust risk forms will be the systems used to manage risk.
Record keeping, in high use departments an audit will be expected to be completed yearly to
ensure that patients requiring entonox have documentation/prescription.
Adverse incident reporting where policy has not been followed, 100% of all incidents reported
to risk management are discussed at mortality and morbidity meetings.
7. TRAINING REQUIREMENTS
Aim
To provide adequate information and knowledge to ensure the safe delivery of Entonox therapy
to patients with acute pain.
Objectives
Staff will be able to:




Define the indications for Entonox
Describe Entonox and its effects
List the contraindications/cautions in the use of Entonox
Demonstrate an understanding of how the associated equipment operates
Workshop
Staff should be prepared by attending an Entonox workshop. An appropriately trained
individual, who has the required knowledge and skill, should deliver this to ensure the
appropriate information is offered effectively and safely. Within the workshop, staff should be
given the opportunity to view the Entonox training videos available from BOC.
Otherwise, sufficient training may be obtained by completing the on-line training package
provided by BOC at http://discover.entonox.co.uk/
A record should be kept of all those taught/updated.
Some staff will have received update/training as part of their preparation for registration. This
should be credited to them on the record/ register. Midwives assume competency to prescribe
and administer Entonox as part of their training.
8. REFERENCES AND ASSOCIATED DOCUMENTATION
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Royal Marsden Manual of Clinical Nursing Procedures. J Mallet and L Dougherty, 8th
Edition 2011
BOC Medical Gas Data Sheet HLC/401840/JIG/APUK/0410/3M (PL 00735/5001R) ©
2009
BOC Educational on-line material: http://discover.entonox.co.uk www.entonox.co.uk
Entonox Medical Gas Data Sheet: HLC/401840/JIG/APUK/0410/3M
Entonox:; everything a parent-to-be needs to know: HLC/402620/JIG/APUK/0609/3M
Entonox; the natural choice for rapid and controlled pain relief during childbirth:
HLC/402610/JIG/APUK/0609/3M
Entonox; conquering procedural pain in children: HLC/402615/JIG/APUK/0609/3M
Entonox; conquering procedural pain: HLC/402605/ JIG/APUK/0609/3M
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
Entonox; controlled pain relief reference guide: HLC/401955/JIG/APUK/0409/2M
9.
EQUALITY IMPACT STATEMENT
Portsmouth Hospitals NHS Trust is committed to ensuring that, as far as is reasonably
practicable, the way we provide services to the public and the way we treat our staff reflects
their individual needs and does not discriminate against individuals or groups on any grounds.
This policy has been assessed accordingly
Our values are the core of what Portsmouth Hospitals NHS Trust is and what we cherish. They
are beliefs that manifest in the behaviours our employees display in the workplace.
Our Values were developed after listening to our staff. They bring the Trust closer to its vision
to be the best hospital, providing the best care by the best people and ensure that our patients
are at the centre of all we do.
We are committed to promoting a culture founded on these values which form the ‘heart’ of our
Trust:
Respect and dignity
Quality of care
Working together
No waste
This policy should be read and implemented with the Trust Values in mind at all times.
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10. MONITORING COMPLIANCE WITH PROCEDURAL DOCUMENTS
Minimum requirement to
be monitored
Lead
Tool
Yearly audit of training and
equipment by Acute Pain
Service, reviewed by BOC
Libby
Burton Smith
Acute Pain database
Risk
management
via
departmental Mortality &
Morbidity meeting
Libby
Smith
Adverse incident report
Burton
Frequency of Report
of Compliance
Annual
Reporting arrangements
Policy audit report to:

Monthly
Acute Pain Service
Policy audit report to:

Lead(s) for acting on
Recommendations
Libby Burton Smith
BOCMedical
representative
Libby Burton Smith
Acute Pain Service
The compliance with his policy will be the responsibility of an Acute Pain Sister.
Monitoring of compliance will be the responsibility of the Acute Pain Service in conjunction with BOC Medical
In the event of a major epidemic or major incident, compliance with this policy
to provide safe administration of entonox for procedures or analgesia.
Entonoxf Policy : Issue Number 6 Issue Date 10/10/2014
change)
may be difficult and will require a risk assessment of the ability
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APPENDIX 1: EVIDENCE BASED PROTOCOL FOR PRACTICE
INITIAL ASSESSMENT
Assess the degree of pain likely for the procedure
being performed
Ensure that Entonox is not contra-indicated for the
patient
Assess individual patient for the ability to use Entonox.
The patient should be able to:
 Understand simple instructions (via an interpreter if
necessary)
 Hold the demand valve and inhale the gas through
the mask or mouthpiece while breathing normally.
If Entonox is considered inappropriate for either the
analgesia should be prescribed.
RATIONALE
To determine whether Entonox is
required
To reduce the likelihood of
complications
To ensure the patient is able to use
Entonox effectively
patient or the procedure, alternative
PREPARATION
Ensure the Entonox has been prescribed on patients Not required in Maternity
drug chart
If Entonox is to be administered more frequently than To observe for :
every four days or for more than 6-12 hours, routine  evidence of megaloblastic
blood cell counts should be performed
change in red cells
 reduced production of
leucocytes
The area should be well ventilated to prevent the To maintain a safe environment.
accumulation of nitrous oxide
The occupational exposure standard
for long term exposure is 100 parts
per million (ppm)
Staff should be trained in the use and To allow staff to be aware of the
applications of Entonox
side effects and occupational
exposure limits of Entonox
Gather and prepare the following equipment:
1. Turn Entonox cylinder on and prime the
To ensure immediate availability of
administration set by pressing the test button on
Entonox
once
inhalation
the back of the demand valve.
commences
2. Check the cylinder to ensure it is at least a quarter
full. If it is not, ring the porter to change the
cylinder.
To reduce risk of infection
3. Attach the filter to mask or mouthpiece before
attaching this to the demand valve
Entonox cylinders should be checked carefully before To prevent drug errors as stronger
use to ensure they contain the correct mix of 50% concentrations of nitrous oxide are
nitrous oxide and 50% oxygen
available in the hospital in similar
cylinders
Ensure that a saturation monitor is available if the To prevent using a cylinder that is at
patient has respiratory or cardiac problems
temperatures lower than -6oC and
has not been left to homogenise at
10oC
To prepare the patient:
To relieve anxiety and determine
level of co-operation
 Explain the procedure to be carried out and how
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Entonox will be used, including information about
the side effects
 Reassure them that if side-effects occur they wear
off quickly once they stop inhaling the gas
The patient should not eat anything for an hour before
procedure. Not applicable to pregnant women in
maternity.
To reduce the likelihood of nausea
and vomiting.
To prepare the patient: continued
Give supplementary analgesia as prescribed:
To provide additional pain relief
 Oral or rectal drugs should be given some time
before starting the procedure, to allow full effect.
 The patient may continue to use their PCA if one is
in progress
 A bolus of intravenous opiate may be given if a
high degree of pain is anticipated
The patient should be allowed to practice using the To ensure an effective technique is
Entonox before the procedure is started
established
If the patient is unable to maintain an effective seal or inhale the gas effectively the use of
Entonox should be abandoned and alternative analgesia and/or sedation should be
prescribed
ADMINISTRATION
To administer the Entonox:
To establish an effective inhalation
 Explain the procedure to the patient. Try to
technique
reassure them & explain that they should
concentrate on breathing normally.
 Offer the demand valve to the patient
 If they have chosen to use a mask they should
hold it over their mouth and nose, maintaining an
airtight seal, and breathe normally
 If they have chosen the mouthpiece they should
hold it between their teeth and breath through their To ensure Entonox has taken effect
before introduction of painful stimuli
mouth only
 Inhalation should commence for at least four
breaths before the procedure starts
The patient may need considerable encouragement to start inhaling the gas. It is worth
persevering as any initial reluctance usually disappears once the patient realises that the
Entonox is working
MONITORING
Once administration has commenced:
To provide effective analgesia with
 The patient should continue to use the Entonox as
minimal side-effects
required throughout the procedure and should be
encouraged to breathe slowly and deeply
 If the patient hyperventilates they should be
To prevent hyperventilation
encouraged to exhale slowly
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Observe the patient throughout the procedure to
determine:
To ensure that adequate pain relief
is provided with minimal side-effects
 Level of pain
 The presence of any side-effects
 Whether they are using the Entonox effectively
Oxygen saturation should be monitored throughout
the procedure if patients have an underlying cardiac
or respiratory condition
If use of Entonox is unsatisfactory at any stage it may be necessary to stop the
procedure until alternative analgesia and/or sedation has been prescribed and given
 If the patient experiences any Entonox related
side-effects they should be reassured, and cease
inhalation until the side-effects wear off and the
sensation of pain starts to return
 For particularly painful procedures it may be
advisable to wait for the patient to recommence
inhalation before continuing
Entonox related side-effects include:
 Earache
 Dry mouth
 Dizziness or disorientation
 Over sedation
 Nausea & vomiting
 Parasthesia in hands and nose
If the patient complains of earache inhalation should
be stopped and alternative analgesia prescribed
A dry mouth is a common side effect but is not usually
distressing. The patient should be encouraged to
continue inhaling the Entonox.
If the patient starts to feel dizzy or disorientated
they may cease inhalation until the sensation
starts to wear off and the sensation of pain
starts to return.
The patient may choose to put up with these
sensations and continue inhalation to maintain
effective pain relief.
If the patient becomes drowsy the seal around
the mask or mouthpiece is lost and they will no
longer inhale the gas.
It is essential that only the patient holds the
mask/mouthpiece
If the patient complains of nausea they should
be encouraged to cease inhalation if they wish
Less commonly the patient may vomit. If so:
 Remove the demand valve immediately
 Reassure the patient and clear any obstruction to
breathing
 Clean and replace face mask/mouthpiece
 Clear vomit from the demand valve by vigorously
shaking it using a “flicking” downward action.
The
patient
may
then
recommence
administration if they wish
To prevent perforation of
eardrum.
To provide effective analgesia
the
To provide effective analgesia with
minimal side-effects
To prevent the onset of deeper
stages of analgesia and sedation
and loss of protection of the
laryngeal reflex
The side-effects of Entonox wear of
quickly once inhalation ceases
To prevent inhalation of vomit
The side-effects of Entonox wear off
quickly once inhalation ceases
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TECHNICAL PROBLEMS
If any of the following technical problems occur they
should be reported to biomedical engineering
immediately:
 Equipment not delivering gas
 Leak at joint between regulator and cylinder
valve
 Demand valve leaks or does not shut cleanly
 Demand valve does not stop giving flow after
test button is released
COMPLETING PROCEDURES
After use :
 Ensure the patient is comfortable

 Check the cylinder gauge for contents:
If less than ¼ full, ring porter to replace the
cylinder (cylinders are supplied on a one-for-one
exchange basis)
 Turn off the cylinder and depressurise the system

fully by operating the test button
Monitoring should continue for 30 minutes to ensure
that the effects of the Entonox have completely worn
off. Accordingly, patients should not walk around
unaided until any dizziness or disorientation has gone

and should be advised to avoid driving or operating
machinery for 30 minutes following administration.
Not applicable in Maternity where there may be the
ambulant use of Entonox.
If the patient has respiratory or cardiac problems they

may benefit from oxygen therapy for 10-15 minutes
after using Entonox
To clean the equipment:
 Depressurise the system
 The external surfaces of the demand valve must
be cleaned with an alcohol-impregnated wipe.
 If any contamination is suspected between the
hose connection & the demand valve it must be
sent to HSDU to be autoclaved.

 Multi-use face masks and mouthpieces must be

autoclaved at 121oC. Single use face equipment
must be discarded
 The external surfaces of the administration set
must be cleaned with an alcohol-impregnated wipe
 Filters are for single patient use and must be
discarded. They may be kept by the patient’s bed if
they are going to use Entonox again within the next
day
Document details of Entonox administration, how
effective it was & any side effects experienced by the
patient
To ensure equipment is safe and in
good working order
To ensure that there is an adequate
supply of Entonox for the next
patient
To prevent misuse and to maintain a
safe ward environment
To maintain patient safety
To prevent post administration
hypoxia
To maintain a safe environment
To minimise the risk of cross
infection
To provide an accurate record of
efficacy and total duration received
by the patient
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Entonox cylinders should be kept in a secure
environment, attached to a wall or trolley and away
from patients when not in use
If the Entonox is used infrequently the cylinder should
be checked weekly and its contents recorded. The
expiry date should also be checked (Entonox has a 3
year shelf-life from date of fill).
RE-ORDERING EQUIPMENT
Entonox cylinders follow internal procedures
product code : 211 size F (QAH), Piped and F size for
the Labour Wards
Masks disposable or reusable follow internal
procedures
Filters follow internal procedures
To maintain safe environment
To ensure equipment is in good
working order
To maintain a safe environment
To ensure equipment is kept in good
working order
To ensure that there
supply on the ward
hospital
To ensure that there
supply on the ward
To ensure that there
supply on the ward
is an adequate
and within the
is an adequate
is an adequate
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APPENDIX 2: ENTONOX FOR USE IN PAEDIATRIC OUTPATIENTS.
Authorised practitioners competent in its use will administer Entonox under a
Patient Group Directive.
Initial Assessment – as per Evidence based protocol for practice Appendix 1.
*Entonox is safe to use with children provided that they are capable of following
administration instructions.
Specific Paediatric Preparation:
*Consider the child’s suitability for use of Entonox, including the child’s ability
and motivation to self-administer the gas.
*Obtain parental/carer cooperation in ensuring that the gas is entirely selfadministered by the child to reduce the incidence of over sedation.
*Obtain age appropriate informed consent or implied consent from the child.
*Encourage parent/carer presence throughout the procedure.
*The child does not need to be fasted.
*Explain the procedure to the child and family/carer in an age/child appropriate
language, including other options available for pain management during the
procedure should the need arise.
*Similarly, explain the potential benefits and side effects anticipated, with
emphasis on how the Entonox might make the child feel.
*Use alternative methods of communication as necessary i.e. Makaton, visual
aids.
*Show the child the equipment to be used and demonstrate the noise
associated with inhaling through the demand valve.
*Choose a mask or mouthpiece as preferred by the child and to optimise ease
of gas delivery.
*Consider using distraction techniques and play as appropriate.
*Allow the child to practice inhaling the gas prior to starting the procedure to
ensure that he/she can activate the demand valve and is confident and
competent with the equipment.
*Ensure the child is in a comfortable and safe position.
During the Procedure
*Ask the child to breathe normally throughout the procedure.
*Allow the child to inhale gas for a few minutes prior to commencing the
procedure to ensure full analgesic effect.
*Use an age appropriate pain assessment tool.
*Continuously assess the child, observing skin colour, and ability to obey
commands, respiratory rate and any signs of pain or distress.
*Observe the child for any side effects.
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Following the Procedure
*Observe the child within the Outpatient Department for thirty minutes following
the procedure.
*It is recommended that the child be supervised by the parents/carers for
between three to four hours following the procedure.
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