Using inhalation sedation in practice

Use of inhalation sedation in a primary care setting

Inhalation sedation with nitrous oxide and oxygen (IS) has been a mainstay of paediatric dentistry for many years in the UK, and has been seen to be a viable and cost-effective alternative to general anaesthesia.^7,8

Where behavioural management techniques alone are insufficient, IS can enable anxious and uncooperative children to manage their dental treatment, and can provide successful treatment outcomes. It is also useful for adults with low to moderate levels of dental anxiety, or for those who may struggle to find an escort for intravenous (IV) sedation. It can also be used as a tool for ‘weaning off’ the need for treatment under IV sedation.

Inhalation sedation has a proven safety record, good success rate, and its properties make it an ideal mild to moderate sedative agent.^9,10,11,12

Relevant guidelines and documents relating to the practice of inhalation sedation

One of the key documents is the 2020 IACSD guideline, ‘Standards for Conscious Sedation in the Provision of Dental Care’ which sets UK national standards for all aspects of dental conscious sedation provision, from environment requirements, clinical delivery to requirements of training for the team providing sedation.⁴ Another key guidance document that helps practitioners meet the IACSD standards is the 2017 SDCEP Conscious Sedation in Dentistry guidelines.⁵

All dentists, doctors and healthcare professionals providing or supporting dental conscious sedation should be aware of, and comply with, these guidelines. It is notable that these documents state that IS is an appropriate form of basic sedation technique for a primary care setting for all ages of children and adults, whereas intravenous midazolam is suitable only for patients aged 12 years and over in primary care.

Other important resources include, although are not limited to: the NICE guideline for sedation in children and young people;⁶ the safe sedation practice for healthcare procedures document produced by AoMRC;² the safe sedation practice scheme;¹³ commissioning dental services: service standards for conscious sedation in a primary care setting;¹⁴ and the CQC website, which sets out the CQC requirements for practice.¹⁵

Patient safety

IS has an excellent safety record. No fatalities or cases of serious morbidity have been recorded for nitrous oxide sedation used for dental treatment, when used alone at levels appropriate for conscious sedation by trained personnel.¹⁶ Lyratzopolous and Blain,¹⁷ in their 2003 review, concluded that nitrous oxide was safe and effective for paediatric sedation as an alternative to general anaesthesia.

Adverse effects of nitrous oxide are rare.¹⁸ The most common side effects, reported in 0.5–1.2% of patients, are nausea and vomiting.^19,20 Longer administration of IS, fluctuations in nitrous oxide levels, lack of titration, higher concentrations of nitrous oxide (over 50%), and a heavy meal pre-operatively are linked to occurrence of adverse events.^21,22 Fasting is not a requisite for patients undergoing nitrous oxide sedation.⁵ The practitioner may, however, recommend that only a light meal be taken within the 2 hours before having IS.²³

The respiratory effect of nitrous oxide, like most anaesthetic gases, is to depress respiration. It reduces tidal volume, but increases respiratory rate, and so the net ventilation is unchanged. Its cardiovascular effects are conducive to treating patients with cardiovascular problems. Nitrous oxide is the only inhalation anaesthetic that does not reduce mean arterial pressure. Cardiac output is in fact increased, as nitrous oxide increases venous tone and venous return. Care should be taken, however, in cardiac defects that result in the respiratory drive being led by low blood oxygen levels. Delivering high levels of oxygen to these patients can reduce the respiratory drive. There are no reported allergies to nitrous oxide itself.

IS is a safe sedative agent for use in practice when treating patients with cardiovascular/cerebrovascular disease, asthmatics, epileptics, cognitive disorders, sickle trait/sickle cell disease (with additional input from physician in charge where necessary), endocrine, hepatic and renal disorders.

There are only a few real contraindications^24,25 to the use of IS. These are subdivided as follows.

Absolute contraindications:

First trimester pregnancy;

Bleomycin chemotherapy: exposure to enriched oxygen should be avoided;

Raised intra-ocular pressure, retinal surgery, recent middle ear disturbance/surgery, intestinal obstructive surgery: nitrous oxide has 15 times the solubility of nitrogen and high doses of IS can cause increased pressure due to gaseous expansion.

Whenever possible and appropriate, medical specialists should be consulted before administering IS to patients with significant underlying medical conditions, such as: severe obstructive pulmonary disease; congestive heart failure; sickle cell disease; acute otitis media; recent tympanic membrane graft; acute severe head injury; and during pregnancy.

Case selection for the primary care setting

The following considerations for selecting appropriate cases in practice at the pre-assessment visit are suggested.

It is not a requirement to fail in a sedation technique before advancing to another treatment option. The most appropriate treatment options for the patient at that specific time must be considered, which may even be a general anaesthetic.

Patient information

Written, age-appropriate information, describing the sedation procedure, must be given to the patient as part of the pre-sedation assessment. This should detail how the patient might feel, along with risks and benefits of, and alternatives to, the sedation. Written pre- and post-operative instructions, along with contact details need to be available for both the patient and the escort.

Useful examples of patient information leaflets can be found in the IACSD document.⁴

Consent

Gaining consent for treatment involving conscious sedation is a legal requirement set out by the GDC.²⁷ This process should begin at the pre-assessment appointment and involve a full discussion with the patient and/or parents/carer regarding the sedation options available, proposed technique and the risks and benefits and alternatives. It should be recorded in the notes that this has been discussed and understood by the patient. Where written consent is obtained at this assessment, it must be reconfirmed on the day of treatment.

Consent obtained only on the day of treatment is not appropriate, except when immediate treatment is in the best interest of the patient.³

The technique^16,23,28

Being a mild to moderate conscious sedation technique, IS requires only clinical monitoring throughout the procedure. Pulse oximetry and blood pressure monitoring are not routinely required. An appropriately trained second assistant is required to support the sedationist.

A quiet, calm surgery is preferable where a patient should be settled and made comfortable. A selected nasal hood should be carefully placed onto the patient's nose, ensuring a good fit and no leaks. The patient should be treated flat, with chin up, to allow a patent airway.

The flow of 100% oxygen should initially be set at approximately 6 l/min, and adjusted accordingly. Nitrous oxide (N₂O) should then be introduced at 10% increments up to 20%, then 5% increments thereafter, at 1-minute intervals of nose breathing, until the end point is reached.^28,29 This is usually around 30%, and can be between 20% and 40% N₂O.³⁰ Caution should be applied at higher doses because concentrations of 50–70% can result in increased detachment, dizziness and a decrease in laryngeal/pharyngeal reflexes.

The patient should be relaxed, responsive to verbal instruction and able to maintain an open mouth. They may start experiencing subjective symptoms, such as feelings of warmth, tingly sensations at the tips of their fingers and toes and sometimes also around their lips, a feeling of being ‘light and floaty’, but arms and legs may also feel heavy, and a lessened response to pain. Spontaneous reduction in movements will be apparent: blink rate decreases, and eyes appear glazed and fixed.

The technique works best when being carried out by an operator/sedationist because they can tailor the use of suitable behaviour management techniques and semi-hypnotic suggestions to the treatment steps. While IS helps support anxiety, it has minimal analgesic effect and appropriate local anaesthesia must still be given for pain control. Nasal breathing should be encouraged and talking discouraged to allow maximum nitrous oxide inhalation. Use of rubber dam, where indicated, is a helpful adjunct in containing the gases within the patient and reducing pollution. As the treatment starts to come to an end and the procedure becomes more or less painless, the patient should be recovered with 100% oxygen for 3–5 minutes to prevent diffusion hypoxia and allow all the nitrous oxide to be expired from the lungs and carried away by active scavenging. Although diffusion hypoxia in a fit and well patient is largely theoretical, it has been linked to post-operative headache and nausea in some patients.³¹

The operator/sedationist and assistant should be vigilant for early signs of oversedation. These are reduced levels of comfort and relaxation, anxiety, distressed look, dizziness and a mild headache along with spontaneous mouth closing.

If the patient appears too heavily sedated, the nitrous oxide concentration should be reduced by 5–10% and re-assessed before continuing treatment. If the patient is more heavily sedated and showing late signs of oversedation, such as extreme anxiety, crying, vomiting and/or severe headache, then treatment should be stopped and the level of sedation checked. Nitrous oxide should be switched off and 100% oxygen given. Once the patient has recovered, the treatment plan should be reassessed.²⁸

Recovery and discharge

It is the sedationist's responsibility to ensure the patient is fit for discharge after the IS episode. The patient should be checked for any headache, nausea or dizziness, and should be coherent and able to walk steadily, unsupported. Nitrous oxide will be entirely expelled via the lungs in 18–20 minutes. The patient may need to wait 10 or so minutes for complete recovery. Post-operative activity, eg school, is at the discretion of the practitioner and also depends on the associated dental treatment received.

Post-operative instructions should be given, both for IS and for the treatment that has been completed, eg warnings about local anaesthesia, post extraction.

An adult patient receiving treatment under IS is not necessarily required to have an escort with them, unless it is deemed so by the sedationist. All patients under 16 years should be accompanied by an appropriate adult.

The authors were not able to find definitive evidence regarding guidance on adults driving after IS. Most practitioners will advise patients to refrain from driving for 2 hours after the inhalation sedation (as per the IACSD information exemplar), however, this should always be based on the individual patients' assessment and discharge criteria.

Setting up and maintaining a safe and effective IS practice

We have discussed the relevant guidance and standard documents related to safe provision of IS, as well as the importance of case selection.

These documents, along with the Safe Sedation Practice Scheme document,¹⁴ provide the mandatory requirements for ensuring the basic prerequisites of sedation standards are met, and a checklist for practitioners to ensure compliance.

Personnel and training

Staff are required both to have appropriate registration and indemnity and to be adequately trained and experienced for the procedures they are carrying out. For dentists, nurses, therapists and hygienists who are new to sedation (post April 2015), this involves undergoing accredited training to gain the necessary skills and knowledge,³ followed by relevant supervised clinical practice. A logbook of sedation cases and experience is recommended.

The 5-year CPD requirement is 12 hours of sedation-related CPD, alongside regular training in sedation-related complications.

Premises

Premises need to be clinically fit for purpose and fulfil legislative and regulatory requirements. Patients must also be able to recover either in the surgery or in a dedicated recovery room, where privacy and confidentiality are ensured throughout.

Policies

Sedation policies should be specific to the practice and the sedation techniques used, following contemporary guidance and standards. Standard operating procedures should relate specifically to the techniques and drugs used, and also include procedures for the handling and management of drugs. If the practice accepts referrals, robust referral criteria need to be in place. There must also be a policy and system in place for reporting critical incidents.

There are useful templates for producing sedation-related standard operating procedures on the SAAD website (www.saad.org.uk), along with a wealth of other sedation-related guidance documents.

Equipment

There are primarily two different types of dedicated inhalation sedation machines for the delivery of nitrous oxide and oxygen: analogue and digital, which can be mounted as stand alone or piped units. Both allow a variable percentage of nitrous oxide and oxygen to be delivered to the patient via a nasal hood or mask. Safety features built into the machines include: an oxygen flush button; an automatic gas cut-out if the oxygen supply fails; minimum oxygen delivery of 30%; colour-coding and pin index system for components and cylinders; gas pressure dials; an air entrainment valve; and some machines have audible alarms when oxygen levels are falling, all of which help to ensure safe and effective delivery of sedation.

Nasal hoods can be single use or autoclavable. They allow delivery of the gases from the common gas outlet to be inhaled through the inspiratory limb and exhaled through the expiratory limb to the attached active scavenging unit. A non-rebreath system prevents waste gases being re-inhaled. Active scavenging systems must be used (see staff safety section below).

Equipment checks must be carried out prior to use, usually at the beginning of the session. These include checking gas levels, calibration of the machine, checking for any leaks in the system, including checking for any perishing of the reservoir bag and gas tubing, checking the automatic oxygen fail-safe device is working, as well as the oxygen flush button. The scavenging system should also be checked prior to use.

Initial investment includes purchase of the machine, tubing and nasal hoods, and the scavenging system. Rental charges of gas cylinders, cost of gases and delivery charges alongside servicing of equipment should also be taken into account.

Health and safety considerations related to safe cylinder storage and handling must be taken into consideration, with appropriate ventilation and signage in place.

Staff safety in the practice

Chronic occupational exposure to high levels of nitrous oxide in unscavenged environments can have toxic effects.^{9, 32, 33}

Recommendations in the UK set the workplace exposure limit (WEL) for nitrous oxide at 100ppm for an 8-hour exposure TWA (time-weighted average) in 24 hours by COSHH (2002).⁹ Various countries around the world have set these exposure limits between 25ppm and 100ppm and have similar legislation.

Factors that affect nitrous oxide exposure to staff in the surgery are:

Recommendations to reduce surgery pollution include:

Clinical governance

Clinical governance and audit are necessary for continuing quality assurance including: ensuring compliance of facilities and clinical environment; carrying out regular sedation-related audits; ensuring protocols and systems are in place for care and management of complications; and systems are in place for reporting critical or significant incidences.

Detailed, contemporaneous notes should be recorded for pre-assessment, consent, sedation, dental treatment, monitoring and recovery and discharge.

Climate impact

It is important to acknowledge current discussions around reducing the climate impact of nitrous oxide use³⁴ by identifying ways of minimizing waste gases and also examining developments of new technologies that can catalyse waste nitrous oxide and reduce it to non-greenhouse gases.³⁵

SAAD and DSTG encourage and support further work in these areas, but recommend the continued appropriate use of nitrous oxide and oxygen for inhalation sedation for children and adults.³⁶

Conclusion

Inhalation sedation is a safe, simple and effective technique for use on mild to moderately anxious patients of all ages. It has been shown to provide successful treatment outcomes, while also being helpful for use with medically compromised patients.

The authors recommend its use within primary care, and find it to be an excellent practice builder, as well as being invaluable in supporting patient care and delivery of treatment.