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PROTOCOL FOR INHALATION SEDATION CLINIC IN CALDERDALE AND KIRKLEES COMMUNITY DENTAL CARE Ian Booth, Clinical Director Prepared by:

Stavriani Papanica, Senior Dental Officer Calderdale & Kirklees Community Dental Care

Responsible Area:

Provider Services Date Approved: 15 August 2007

Approval Information: COMMITTEE: PEC Lead Director:

Robert Flack Version No. Approved:

Reference to Standards for Better Health Domain

Core/Development standard Performance indicators

June 2007

June 2008 Review Date: Department of Health 2004 Standards for Better Health First domain Safety Second domain Clinical effectiveness Third domain Governance Fourth domain Patient focused Fifth domain Accessible and responsive care Sixth domain Care environment C5 D2 C7

Indicators not required for this protocol, as agreed by Performance Management

History of Document Version 1


CONTENTS Section No.

Page No’s

1.

Introduction

3

2.

Indications/contraindications for inhalation sedation

4

3.

Referral to sedation clinic

5

4.

Staff Monitoring

6

5.

Machine check list

7

6.

Patient assessment & preparation for sedation

8

7.

Drug administration & requirements for treatment

9

8.

Recovery – abandoned treatment

10

9.

Post-operative check list

11

10.

Moving & handling

11

11.

Staff training requirements

12

12.

Appendices

14

NICE Guidance Once NICE guidance is published, health professionals are expected to take it fully into account when exercising their clinical judgement. However, NICE Guidance does not override the individual responsibility of health professionals to make appropriate decisions according to the circumstances of the individual patient in consultation with the patient and/or their guardian or carer.


Introduction Definition of sedation ‘A technique in which the use of a drug or drugs produces a state of depression to the central nervous system enabling treatment to be carried out but during which verbal contact with the patient is maintained throughout the period of sedation. The drugs and techniques used to provide conscious sedation for dental treatment should carry a margin of safety wide enough to render loss of consciousness unlikely’ – General Dental Council The goals of sedation when used together with local analgesia for the provision of dental treatment are: 1. to guard the patient’s safety and welfare 2. to minimize physical discomfort and pain 3. to control anxiety, minimize psychological trauma, and maximize the potential for amnesia 4. to control behaviour and/or movement so as to allow the safe completion of the procedure 5. to return the patient to a state in which safe discharge from medical supervision, as determined by recognized criteria, is possible. The present protocol is aiming to set the layout and facilitate the provision of dental treatment under inhalation sedation within the Calderdale and Kirklees Community Dental Care clinics. It will be subject to annual review and update in line with the current General Dental Council recommendations.

Indications for inhalation sedation Inhalation sedation is primarily indicated for the management of dental anxiety. It should be viewed as part of an overall behaviour management strategy. Relative analgesia with nitrous oxide (RA) is indicated for the above patient categories: 1. 2. 3. 4. 5. 6. 7. 8.

Anxious or fearful patients Needle phobic patients Where profound analgesia is difficult to obtain (e.g. acute pulpitis) Increased gag reflex Increased tooth sensitivity (e.g. hypoplastic teeth) Prolonged or unpleasant treatment (e.g. surgical treatment) Persistent fainting For special needs/medically compromised patients with sufficient level of intellectual ability and communication, as an alternative to treatment under general anaesthesia 9. Cardiovascular disorders (as it reduces anxiety, elevates pain threshold and provides increased levels of oxygen) 10. Liver/ kidney disease (as it does not undergo biotransformation in the body)


11. Sickle cell disease or trait (as high levels of oxygen are provided throughout treatment) 12. Severe asthma (as high levels of oxygen are provided throughout treatment)

Contraindications to Inhalation sedation The contraindications to nitrous oxide inhalation sedation are only relative. In all cases it is necessary to balance the risk of giving the patient sedation against the risk of administering general anaesthesia (which otherwise would be the only available option for many of the above patients). The contraindications to inhalation sedation are: 1. Inability to communicate 2. Very young, pre-cooperative children (due to reduced perceptive ability and incapability to follow instructions and to communicate – although each case should be assessed on its own merit) 3. Unwilling/unable to nose breath (obstructed nasal airway / mouth breathing) 4. Cold/rhinitis 5. Otitis media (due to pressure volume effects), sinusitis or recent ENT operations (within 14 days) 6. Chronic obstructive airways disease (e.g. emphysema, chronic bronchitis) because the lowered blood oxygen level is the stimulus for breathing 7. Severe muscular depression (e.g. Multiple Sclerosis) 8. Severe psychiatric disorders 9. Behavioural/personality disorders or history of drug abuse 10. Learning difficulties 11. Psychological problems/ fears e.g. fear of ‘loss of control’, fear of the mask, claustrophobia 12. First trimester of pregnancy 13. Patients in chemotherapy with bleomycin or methotrexate 14. Patients with porphyria

Referral to Sedation clinic A. In-service referral: •

• • • • • •

Patient seen previously by dental officer (with/without previous treatment attempts) and assessed suitability for RA clinic. Medical history with emphasis to the before mentioned contra indications will need to be thoroughly checked. RA referral form to be filled / dental notes to be forwarded to clinic All relevant radiographs to be taken RA info booklet to be given to patient Patient’s name to be placed in RA waiting list – if required Arrange for patient’s records to be transferred to the sedation clinic Patient to be booked for RA assessment by the delegated Senior Dental Officer(s) coordinating the sedation clinic.


• •

Patient to be given Preventive Dental Unit appointment Senior Dental Officer to see patient for assessment visit, when the patient’s suitability for RA will be assessed and possibly an introductory procedure will be carried out at this visit. Consent forms for treatment under RA (Kirklees PCT NHS consent forms 1 & 2) to be signed

B. GDP referral: •

Patient to be seen for initial examination (not RA assessment) by any dental officer within the service, when a thorough discussion on the available treatment options/ risks/benefits and alternatives will identify whether the patient meets the criteria for RA referral in our service or other treatment options will be more appropriate If patient is suitable for RA treatment, then proceed as above

Factors to consider prior to referring patients to sedation clinic Prior to referring patients to sedation clinic the suitability of each individual patient should be assessed on its own merit. In addition to the above mentioned indications there are some significant factors to be taken under consideration prior to decision taking, such as: i. ii. iii. iv. v. vi.

vii.

The extent of treatment required Previous attendance history Caries risk group Patient’s motivation for oral health Risk of general anaesthesia for the individual patient Developmental stage of the patient and ability to understand, comply with simple instructions and maintain communication (with the exemption of acute conditions requiring minimal number of visits i.e. emergency extraction of traumatised teeth in a very young child) Consent issues

Monitoring of staff In order to monitor staff exposure to nitrous oxide, it is essential that all staff involved to the sedation clinic will be subjected to monitoring. The Occupational Exposure Standards for nitrous oxide, as defined by the British Health and Safety Commission (1995) is 100ppm over an 8 hour weighted time average (TWA). Personal monitoring tubes (diffuse samplers) will be used for the above purpose, and they will need to be worn as label badges as close as possible to the individuals breathing zone. The monitoring will take place during one full session/ or full day, depending on the individual circumstances. The operator, the dental nurse and one extra person (who will be within the dental department, but not in the vicinity of the gases) are required to be monitored simultaneously. On completion of the sampling, the monitors will be collected and sent for analysis at the Chemical and Pathology Lab, Britannia House, Leeds. A detailed report, containing the results and including comments, conclusions and comparison against the occupational exposure limits, will be sent to the clinic in short time. In case


that the results are within the accepted levels then further monitoring of staff will be required every 6 monthly, unless adverse effects reported. In case that the monitoring results fall outside the set limits, the case will be followed up further by the Chemical and Pathology Lab, Britannia House, Leeds in order to identify causes of overexposure and advise on best practice. Monitoring of the involved staff will be repeated as per instructions. Monitoring should involve all new equipment, all environments in which the gases will be used or stored and all operators/nursing staff. In addition, monitoring of nitrous oxide levels is required if adverse effects are reported by staff and it is desirable if pregnant employees are in vicinity. For the monitoring of the anaesthetic equipment and any necessary service required, the service engineer will need to be contacted. The initial monitoring of the equipment must take place at the time of the installation, and then regular 6 monthly checks are required. All environmental monitoring reports must be retained in the RA Sedation Clinic file for future reference. All personal monitoring reports must be kept in the member of staff’s personnel file.

Occupational risk during pregnancy, fertility treatment or family planning As nitrous oxide can have adverse effects on fertility and pregnancy all staff who may fall into these groups should arrange for an individual case assessment by the occupational health. As a general advice exposure to nitrous oxide gases should be avoided. In case of pregnancy an assessment as early as possible is recommended as the first trimester of pregnancy is a critical period in the foetal development and nitrous oxide exposure has been associated with increased risk of spontaneous miscarriages.

Machine Check List (a laminated copy to be kept on the machine at all times) The machine check list aims to check: • Contents of all gas cylinders • Correct functioning of controls and flow meters • Automatic cut-out of nitrous oxide flow • For leaks at the reservoir bag, cylinder circuit and regulators STEPS: Start with ALL cylinders off. Switch on machine. GAS check (full cylinders first): 1. open ‘FULL’ O2 cylinder Æ pressure gauge rises 2. open ‘FULL’ N2O cylinder Æ pressure gauge rises BLEED check: 1. open flow control with mixer control set at 30% N2O 2. switch off both cylinders (nitrous oxide first) 3. both flow meters fall to ZERO


GAS check (in use cylinders): 1. open ‘IN USE’ O2 cylinder Æ pressure gauge rises 2. open ‘IN USE’ N2O cylinder Æ pressure gauge rises 3. turn off cylinder valves Æ cylinder contents valve gauge needles do not fall FLOWMETER and CONTROLS check: 1. 2. 3. 4.

turn ‘IN USE’ cylinders back on set mixer control at 100% O2 open flow control Æset flowmeter at 6 litres/minute O2 set mixer at 50% O2 (50%N2O) Æ check calibration (equal flows +/0.25litres/minute) 5. turn off O2 cylinderÆ flowmeter drops to ZERO (automatic cut-out)

RESERVOIR BAG & CIRCUIT checks 1. 2. 3. 4. 5. 6. 7.

turn O2 cylinder on turn off flow control set mixer at 100% O2 occlude common gas outlet press O2 flush Æ reservoir bag inflates Æcheck for leaks examine all flexible pipe work for visible damage ensure scavenging is properly connected and switched on

All safety checks should be performed at the beginning of the session, and whenever possible full checks should be repeated between patients. It is essential that there is always one full cylinder for each of the gases at the machine at the beginning of each treatment procedure, and any empty cylinders are replaced immediately at the end of the treatment. A safety checks log book will be kept at the clinic and all checks must be recorded dated and signed by the nursing staff on duty. There will be also space for any comments for each entry. Any failures of safety checks must be reported immediately to the Medical Physics department at Dewsbury District Hospital/Huddersfield Royal Infirmary/Calderdale Royal Hospital and may result in cancelling of patients until they will have been addressed appropriately. In case of an emergency situation (i.e: gas leak at storage area) the Medical Physics department at Dewsbury District Hospital/Huddersfield Royal Infirmary/Calderdale Royal Hospital must be contacted immediately. In case of suspected problems in the storage room the windows must be left open to allow natural ventilation and the room should be evacuated immediately (with fire doors closed) until further advice by Medical Physics. The room temperature for the cylinder storage must remain below the critical temperature (36.4 C) at all times and direct exposure of cylinders to sun light or extremes of heat/cold must be avoided. Monitoring of the room temperature should be


recorded on a daily basis, in case that room temperature is not regulated by central system of the building.

Patient assessment After receiving a patient referral for sedation (in-service referral form only) the patient will be invited for an initial assessment appointment that will involve the following: • Completion of a medical history questionnaire and a fear survey (where available). RA treatment is available for ASA I & II patients. • History, clinical and radiographic examination (evaluation) • Assessment of cooperation and ability to follow simple instructions (e.g. nose breathing) • Physiological assessment and baseline records including: 1. weight (kg), height (m) 2. pulse rate/ heart rate 3. oxygen saturation 4. respiration rate 5. colour and temperature 6. airway patent (i.e. any nasal, tonsillar obstruction, history of mouth breathing, sleep apnoea etc) • Discussion with patient/parent regarding the risks/benefits of RA and the alternatives in pain and anxiety management in dentistry. • Discussion on the proposed treatment plan • Informed consent to be obtained and NHS consent form 1 or 2 to be signed prior to treatment

Pre- and post-operative instructions to be given (verbal and written) by the sedation nurse (in the dentists presence) Presence of an accompanying responsible adult and the need to arrange suitable post-operative transportation and supervision will need to be highlighted

A sedation appointment will then be arranged – usually an RA trial to assess the patient’s response

Sedation Appointments Appropriate personnel: • One trained dentist with appropriate sedation qualification who will act as the sedationist and will also provide the dental treatment • Wherever possible two dental nurses are advisable – one for monitoring the patient’s vital signs and recording them and one for assisting the dentist. Where only one dental nurse is present, they will work according to the clinician’s discretion and must be sedation competent (see staff training section). The dental nurses should be suitably trained in inhalation sedation and trained and regularly updated in basic life support. Safety checks and availability of all monitoring, sedation and emergency equipment will be recorded prior to sedation session by the dental nurse in charge of the session and each entry must be dated and signed.


Pre-operative patient check-list forms must be filled in by the dental nurse, signed by the parent and checked by the dentist prior to treatment. Regular team meetings with emergency practice procedures will be carried out on a 3 monthly basis.

Patient preparation - Fasting Prior to conscious sedation it is recommended, that the patient shall consume clear fluids/light meal no later than two hours before sedation. Clear liquids are non-fruity juice, water, tea, and coffee. All milk products (nonclear liquids) are considered as solid foods. Children under school age shall drink sugar containing clear liquid up to 2 hours before treatment in order to avoid low blood sugar. For the emergency patient, where proper fasting has not been assured, the increased risk of sedation must be weighted against the benefits of the treatment, and the lightest effective sedation should be used. If possible, such patients may benefit from delaying the procedure.

Drug administration – Requirements for treatment RA nitrous oxide/oxygen sedation is given throughout the operative procedure, and usually there is a 3-10 minutes induction period with semi-hypnotic suggestion. The titration technique is recommended. The depth of analgesia is indicated by the patient’s reactions and the flow of gases adjusted accordingly in steps of 5-10%. The RA machine should have an upper limit of 70% N2O (therefore a lower limit of 30% O2) by volume, although in most cases adequate relative analgesia is achieved with lesser concentrations of nitrous oxide that do not exceed the 50% by volume. The machine must be dedicated for RA use only – not a dual RA/GA machine to be used. The RA equipment should be maintained and serviced to manufacturer’s instruction and a service history book must be kept in clinic. Active scavenging system must be used during treatment, and patient should be encouraged to minimise mouth-breathing and talking in order to avoid gas pollution in surgery. Scavenging equipment should be maintained and serviced to manufacturer’s instruction and a service history book must be kept in clinic (as above). The duration of dental treatment can vary, taking up to one hour. Treatment will be carried out under rubber dam (when appropriate) in order to protect the airway. Use of mouth props is not indicated, as inability to keep the mouth open is a sign of deeper sedation level, which should be avoided. During the procedure careful clinical monitoring is required with use of pulse oximetry. The concentration of gases (%) and their total flow (L/min), the colour of the patient,


respiratory rate, oxygen saturation, as well as the length of the visit should be recorded during the several stages of dental treatment. For that purpose RA stickers will be used, which will be affixed in the patient’s notes (see Appendix). In addition, it is important to record patient’s cooperation/behaviour rate, as higher gas levels can be explained by poorer compliance/ cooperation during procedure (increased pollution risk). The assessment of cooperation will be recorded using the Frankl/Wright scale and the Global Houpt rating (see Appendix) Wide bore suction, kidney dishes and oro-pharyngeal airways (sizes 1, 2, 3 - 1 of each) must be available at all times during treatment under inhalation sedation. Emergency drugs kit should also be present in clinic. In completion of the session the patient should have 100%O2 for at least two minutes.

Recovery Recovery is generally uneventful but supervision is required. The effects of nitrous oxide can be reversed quickly by providing the patient with 100%O2 for at least two minutes. Although a dedicated recovery nurse/assistant is not always necessary, the presence of a dental nurse during recovery is essential. The dental nurse should stay with the patient until recovery is deemed sufficiently complete and the patient is fully awake, responsive, and able to walk unassisted. The patient must be discharged to a responsible adult/parent/carer and must have arranged transport by car or taxi for the journey home (not public transport). Time of dismissal must be recorded.

Abandoned treatment Unsuccessful sedation will be evaluated for cause. If adjustment of dose is not appropriate then the patient/parent will be advised of alternative management methods (i.e. other sedation techniques, treatment under general anaesthesia etc)

Post-operatively – Dental nurse check list At the end of the session the dental nurse who remains in surgery must: 1. Turn off the RA machine: • First close down the N2O valve and drain off • Then close down the O2 valve and flush out 2. Change any cylinder that is empty and test – ensure that ‘in use’ and ‘full’ cylinder labels are in place 3. Switch off scavenging


4. Switch off pulse oximeter 5. Return RA machine to storage place 6. Return pulse oximeter to recovery room 7. Autoclave nose piece (outer nose piece and inner liner if autoclavable or discharge inner liner if single-use) 8. Autoclave breathing circuit

Moving and handling The moving and handling of the gas cylinders must be according to Kirklees PCT Health and Safety policies. Extra care must be paid when replacing empty cylinders from storage and under no circumstances a gas cylinder (full or empty) will be moved without use of appropriate aids (trolley). Alternatively the RA machine cylinders’ stand can be used for that purpose (wherever possible), in order to allow immediate replacement of the cylinders and to minimise moving and handling efforts. The gas supplier company will be responsible for removing empty cylinders from their storage and replacing them with full ones (dental staff should refrain from moving/handling the cylinders in that case). A delivery of full gas cylinders must be arranged when the two or three of the clinic’s stock is running out. Staff must ensure they allow adequate time for the delivery, as an urgent request of the cylinders will have increased financial implications to the service.

Staff training requirements Following the recommendation of the Royal College of Surgeons of England (2002), it is essential that all staff involved to the provision of inhalation must undergo appropriate training on a regular basis as determined by competent authorities. Also the basic life support skills must be updated on a regular basis. It is essential that primary care dentists who sedate children undergo training that is recognized by appropriate authorities and that their clinical skills and knowledge relating to paediatric conscious sedation, including local anaesthesia, behavioural management and the provision of operative dental care for children, is updated as part of continuing professional development. Specialist paediatric dentists are expected to have acquired the necessary skills and competency for nitrous oxide inhalation conscious sedation, but such individuals are still obliged to keep themselves updated and to adhere to national and regional policy and procedure. The dental nurses should be appropriately trained in sedation techniques as well as in basic life support skills. Attainment of the Certificate in Dental Sedation Nursing (CDSN) from the National Examining Board for Dental Nurses (NEBDN) is strongly encouraged.


In-house training program is also available in the service and should be part of the continuing professional development for the dental nurses wishing to be involved in the sedation clinic.

In-House training for dental nurses The in-house training of the dental nurses will provide the dental nurse with the skills to assist the clinician during the provision of dental treatment under inhalation sedation. The dental nurse must be competent to: 1. set the surgery and prepare the equipment for the sedation session 2. perform the safety checks at the machinery 3. monitor the vital signs of the patient during treatment sedation 4. monitor the equipment during the treatment 5. give appropriate pre- and post-operative instructions 6. monitor the post-operative recovery of the patient 7. provide basic life support 8. have some advanced theoretical background on the use of nitrous oxide as sedative agent and be aware of the occupational risks 9. comply with COSHH regulations 10. act in accordance with risk and safety procedures 11. comply with monitoring protocols At the beginning of the training each candidate will be allocated a handout with appropriate references on the theory of the Nitrous Oxide Inhalation Sedation. During the in-house training it will be required that each trained nurse attends a predetermined number of cases (usually 24 cases) assisting a senior dentist. The dental nurse must maintain a clinical log-book to record all sedation sessions that he/she has assisted and the type of work that was performed. Each entry must be signed by the operating senior dentist. After the completion of the pre-determined number of cases, a practical competency test followed by a short written examination on the theory of Nitrous Oxide Sedation will accredit the dental nurse with the competency to assist sedation sessions on a regular basis. The competency tests will be organized by the Coordinator of the Sedation Clinic. An Inhouse training certificate will also be provided on the successful candidates.


Example of the log book: Cases with assisting duties 1 2 3 4 5 6 7 8 9 10 11 12 Cases with monitoring duties 1 2 3 4 5 6 7 8 9 10 11 12 Practical Test Surgery set- up Pass/ Fail

Date

Name of patient

Dentist

Treatment performed

Behaviour rating (Frankle score)

Other comments

Signature

Date

Name of patient

Dentist

Treatment performed

Behaviour rate (Frankle score)

Other comments

Signature

Monitoring equipment Pass / Fail

Pre/post op instructions Pass / Fail

Recovery assistance Pass / Fail

Final outcome: Competent / To repeat exam

Safety Monitoring patient checks Pass/Fail Pass/Fail


APPENDICES

I. II.

ASA classification Nitrous oxide data(properties/ pharmacology, effects- occupational exposure risks) III. In-service RA ref. form IV. Pre-post op instructions leaflet for patients V. RA recording sticker VI. Clinic pre-op checks page as an example for record book VII. Frequently asked questions VIII. Literature references [DoH policy (2002), EAPD policy (2003/4), BSPD (2002), Standards in Conscious sedation for Dentistry – SAAD (2000)]


Appendix I

ASA CLASSIFICATION


Physical-Status Classification of the American Society of Anaesthesiologists (ASA)

Class Physical status I

A healthy patient with no systemic disease processes

II

A patient with mild to moderate systemic disease process caused either by the condition to be treated surgically or other pathological process and which does not limit the patient’s activities in many ways, e.g. diabetic, treated hypertensive or smoker

III

A patient with severe disturbances from any cause, and which imposes a definite functional limitation on him or her, e.g. ischemic heart disease with a limited exercise tolerance, severe chronic airways with dyspnoea on exertion

IV

A patient with severe systemic disease that is a constant threat to life, e.g. with chronic bronchitis who is dyspnoeic at rest

V

A moribund patient who is unlikely to survive with or without surgery

E

Emergency operation: any patient in any of the above grades who is operated on as an emergency is regarded as being in poorer physical condition

Inhalation sedation with Nitrous oxide will be available in our premises only for ASA Class I and II patients. Patients belonging to ASA Class III and Class IV can be treated with the help of nitrous oxide/oxygen sedation provided other indications are present, but treatment of these patients must be restricted to hospital settings, where an anaesthetist can be present.

These guidelines include a number of terms which are defined below: Must or shall: Indicates an imperative need or duty that is essential, indispensable, or mandatory. May or could: Indicates freedom or liberty to follow a suggested or reasonable alternative.


Appendix II

NITROUS OXIDE DATA


NITROUS OXIDE: N2O Nitrous oxide ("laughing gas") is a stable, colourless anaesthetic gas. It is has a slightly sweet smell and taste. It isn't irritating to the mucous membranes and it is relatively safe, if used mixed with at least 30% Oxygen.

Safety (MSDS) data for nitrous oxide

General Synonyms: dinitrogen monoxide, factitious air, laughing gas Molecular formula: N2O , CAS No: 10024-97-2 , EC No: 233-032-0

Physical data • • • • • • • • • • • •

Molecular weight: 44.02 Solubility in water - 1 litre of gas in 1.5 litre of water at 20°C and 2 atm. Boiling point: -88.46°C (at atmospheric pressure) Melting point: -90.81°C (at atmospheric pressure) Density as a gas: 1.997 mg/cm3 at 0°C at atmospheric pressure Vapour pressure: 4.93 pascals (at 20°C) (50.8 bar) Vapour density: vapour 1.5 (air = 1) Relative molecular mass: 44.02 Viscosity: 1488.99 poise (at 27°C) Specific gravity: 1.529 at 0°C, at atmospheric pressure. Appearance: Colourless gas with sweetish odour Critical temperature: 36.4 C

Stability It is oxidant and strongly supports combustion. Its thermal decomposition yields toxic products

Toxicology Inhalation in high concentration may cause asphyxiation. Low concentrations may cause narcosis. Risk phrases R8: Contact with combustible material may cause fire.

Transport information Major hazard class2.2: Non-flammable, non-toxic gases Subsidiary hazard class 5.1. : Oxidizing agents


Personal protection Good ventilation. Safety glasses when using compressed gas or vacuum equipment. Safety (S38): In case of insufficient ventilation, wear suitable respiratory equipment. French blue cylinders are used to store N2O in a liquid phase with its vapour on top at a gauge pressure of 4400 kPa at room temperature. As the liquid is less compressible than a gas, the cylinder should be only partially filled. The filling ratio is the weight of the fluid in the cylinder divided by the weight of water required to fill the cylinder. In the UK, the filling ratio for N2O is 0.75, but in hotter climates the filling ratio needs to be 0.67, to avoid cylinder explosion. Hospitals store N2O in large cylinders (e.g. size J) in two groups of cylinder manifolds.


Pharmacokinetics of Nitrous Oxide The forward movement of inhalational agent is determined by a series of partial pressure gradients, beginning at the vaporizer of the machine, continuing in the breathing circuit, the alveolar tree, blood, and then tissue. The principal objective of that movement is to achieve equal partial pressures on both sides of each single barrier. The alveolar partial pressure governs the partial pressure of the anaesthetic in all body tissues; they all will ultimately equal the alveolar partial pressure of the gas. After a short period of equillibration the alveolar partial pressure of the gas equals the brain partial pressure. Thus the alveolar partial pressure can be raised by increasing minute ventilation, flow rates at the level of the vaporizer and by using a non-rebreathing circuit (not relevant for dental sedation).

The concentration effect The concentration effect describes how the concentration of the gas in the remaining alveolar volume can increase after some of the gas has been transferred into the blood. Thus, the concentration effect states that with higher inspired concentrations of an anaesthetic, the rate of rise in arterial tension is greater. N2O has a low blood:gas partition coefficient (relatively insoluble in blood)and therefore it has a rapid onset and offset of action (see notes below regarding the blood/gas coefficient). N2O is about 20 times more soluble than O2 and N2. During induction the volume of N2O entering the pulmonary capillaries is greater than the N2 leaving the blood and entering the alveolus. As a result the volume of the alveolus decreases, thereby increasing the fractional concentration of the remaining gases. This process augments ventilation as bronchial and tracheal gas is drawn into the alveolus to make good the diminished alveolar volume.

Diffusion Hypoxia This is effectively the reverse of the above. The elimination of a poorly soluble gas, such as N2O, from the alveoli may proceed at as greater rate as its uptake, (The volume of N2O entering the alveolus is greater than the volume of N2 entering the pulmonary capillary blood.), thereby adding as much as 1 l/min to alveolar air. This gas effectively dilutes alveolar air, and available oxygen, so that when room air is inspired hypoxia may result. This is usually only mild and rarely clinically significant although this may occur with any anaesthetic agent, its magnitude is insignificant unless an insoluble agent, such as nitrous oxide, has been inhaled for some time.

Blood:gas coefficient The solubility of a gas in liquid is given by its Ostwald solubility coefficient. This represents the ratio of the concentration in blood to the concentration in the gas phase. This is independent of pressure, obeying Henry's law, serum proteins and RBC's are the major determinants of solubility.


Solubility describes the affinity of the gas for a medium, such as blood or fat tissue. The blood/gas partition coefficient describes how the gas will partition itself between the two phases after equilibrium has been reached. A higher blood/gas partition coefficient means a higher uptake of the gas into the blood and therefore a slower induction time. It takes longer until the equilibrium with the brain partial pressure of the gas is reached. The blood /gas coefficient for Nitrous oxide is 0.47.

Effects CNS The gas is analgesic in concentrations above 20%. In concentrations of 80% will cause loss of consciousness in most subjects. It increases cerebral blood flow and should be avoided in patients with raised intracranial pressure.

Cardiovascular The mean arterial pressure is usually well maintained by a reflex increase in peripheral vascular resistance.

Respiratory N2O is non-irritant and does not cause bronchospasm. It causes a small fall in tidal volume that is offset by an increase in respiratory rate so that the minute volume and CO2 remain unchanged. It may cause diffusion hypoxia at the end of surgery. It expands air-filled cavities because it is 40 times as soluble as nitrogen; thus, it passes from the blood into the cavity faster than nitrogen can diffuse out.

Gastrointestinal tract Nitrous oxide can cause the expansion of gas-containing bowel. It is associated with postoperative nausea and vomiting.

Other N2O does not affect renal or hepatic function, or uterine or skeletal muscle tone.

Elimination Nitrous oxide is excreted unchanged through the lungs and skin.

Toxicity Methionine synthetase appears to be directly inhibited by N2O, which also oxidises the cobalt ion present in vitamin B12, so that it is unable to act as a


cofactor for methionine synthetase. The result is reduced synthesis of methionine, thymidine, tetrahydrofolate and DNA. Prolonged use of high concentrations of N2O (>6 hours) can result in clinical syndromes akin to pernicious anaemia, megaloblastic anaemia and pancytopenia. Protracted use of the gas may also lead to the development of a peripheral neuropathy or a neurological syndrome that resembles subacute combined degeneration of the cord. Nitrous oxide is teratogenic in animals when administered during early pregnancy. Experimentally, this effect is prevented in rats given folinic acid; however, this has never been demonstrated unequivocally in humans.

Contraindications to Nitrous Oxide N2O should not be used for patients with bowel obstruction, pneumothorax, middle ear and sinus disease, and following cerebral air-contrast studies. Many anaesthetists feel that use of N2O should be restricted during the first two trimesters of pregnancy because of its effects on DNA production and the experimental and epidemiological evidence that N2O causes undesirable reproductive outcomes. Since N2O affects white blood cell production and function, it has been recommended that N2O not be administered to immunosuppressed patients or to patients requiring multiple general anaesthetics

Occupational Health and Safety Chronic exposure to nitrous oxide has been reported to constitute an occupational health hazard. The adverse effects of chronic exposure can be categorised as above:

• Haematological (Reduced red cell production, anaemia, reacts with metal complexes)

• Immunological (Bone marrow- megaloblastic haematopoiesis and leukocytes mainly affected)

• Neurological (peripheral neuropathy, spinal cord degeneration, paraesthesia / numbness)

• Reproductive (Reduced fertility, spontaneous miscarriage, congenital malformations, testicular changes)

• Organ (dys)function (Mainly liver and kidney)

• Malignancy


Nitrous oxide interferes with Vitamin B12 (causes deficiency) as well as the DNA synthesis (affects the enzyme methionine synthetase). Vitamin B12 deficiency may cause neurological and psychiatric disturbances including depression, dementia, and a demyelinating myelopathy (affects CNS function). Disturbances in DNA formation can cause chromosomal abnormalities, cytotoxicity and may have mutagenic potential. It has been reported that there is a 6%reduction in chances of conception each menstrual cycle for each hour per week of exposure. Consequently, the dental staff must follow strict indications for the use of nitrous oxide, only use nitrous oxide delivery systems with an efficient scavenging system, have appropriate technique for disconnection of the delivery system, and have methods for testing the integrity of the breathing system. It is also advisable (after discussion with their doctor), to take B12 supplements, especially if they are strict vegans and vegetarians, as B12 vitamin can only be found in animal foods and products.


Appendix III

In Service Referral Form


CALDERDALE & KIRKLEES COMMUNITY DENTAL CARE - PCT

Inhalation Sedation Referral Form (to be placed on RA waiting list) Name:…………............................................................... D.O.B:……/…../…… M/F Age: …… Address:………………………… …………… Tel no: …………………… Weight: ……… (kg) Estimated number of visits………….. Routine / Urgent Referring staff: ………………………….. Date : ..…/…../….. Date placed on w.list: …../…../…..

Fulfills criteria for

Appropriate

sedation □

radiographs □

Info leaflet given □

Consent □

Relevant medical history Current medication Sleep apnoea/tonsilla Yes □ obstruction Able to understand / Yes □ follow instructions Previous sedation/GA Yes □ Parent / other adult w Yes □ accompany?

No

No

□ No □ No

Able to breath through Yes □ No the nose Cooperation Frankle :++, +, -, -If yes give details:

Having own means of Yes □ No transport (no public transport)

Treatment planned under inhalation sedation: • ……………………………………………................................................................ • ……………………………………………………………………………………… • ……………………………………………………………………………………… • ……………………………………………………………………………………… • ……………………………………………………………………………………… • ……………………………………………………………………………………… The patient/parent/guardian has been informed about the treatment to be provided under inhalation sedation including the risks/benefits of such treatment and the alternative strategies available. Signed: Date: /

Name: /


Appendix IV

Pre- & Post operative instructions - Patient leaflets (Children and adults versions)


CALDERDALE & KIRKLEES COMMUNITY DENTAL CARE - PCT

Inhalation Sedation – Relative Analgesia Patient Information Leaflet - Sedation in children

Q: What is inhalation sedation? A: It is a behaviour management technique that uses a mixture of a sedative gas (called Nitrous Oxide or more commonly ‘Laughing Gas’) and Oxygen to assist the child to cope with fear and anxiety and cooperate with dental treatment. The dosages that are administered are very unlikely to cause loss of consciousness in the patient.

Q: Who could be sedated? A: Best candidates are children who have a level of anxiety that prevents good coping skills. Inhalation sedation is also very useful for people with increased gag reflux. It could be also helpful for the very young children who do not understand how to cope in a cooperative fashion for the delivery of dental care. Additionally, this form of sedation is often helpful for some children who have special needs and have limited ability to cope for dental procedures.

Q: Why utilize inhalation sedation?


A: This form of sedation aids in allowing the patient to cope better with dental treatment and to relieve stress and anxiety reducing thus the need for more advanced pharmacological sedation or general anaesthesia. It is a very helpful tool in the behaviour management of the phobic patient as it helps the desensitization process. The patient does not loose consciousness during treatment being thus able to come in terms with his/her dental phobia and confront his/her fears. In case of hyperactive/overactive children it can also prevent injury to the child from patient movement and promote a better environment for providing dental care. It is also a very valuable aid to control an increased gag reflux. Additionally it can provide some degree of supplementary analgesia in those cases that numbing the teeth with a local anaesthetic alone is problematic or insufficient.

Q: Is Inhalation Sedation safe? A: Careful pre-sedation evaluation is very important. Your dentist will ask you to fill a medical history form prior to your assessment appointment and will discuss with you any particular concerns prior to treatment. Generally speaking dental treatment under Nitrous Oxide inhalation sedation is a safe technique as it provides continuously high levels of oxygen all the way through treatment (at least 30% oxygen is administered when the atmospheric air contains only 21%). In addition the patient’s vital signs are monitored and recorded for the duration of treatment. Your dentist will discuss in more details the risks, the benefits and the alternatives to the Nitrous oxide sedation.

Q: What special instructions should I follow before the sedation appointment? A: In order to alleviate potential anxiety in your child, your dentist may recommend minimal discussion of the dental appointment with your child.


It is very important to follow the directions of your dentist regarding fasting from fluids and foods prior to the sedation appointment. We recommend that fluids and a light meal should be taken not later than 2 hours prior to the sedation appointment to minimize the risk nausea and vomiting (common side effects when Nitrous Oxide gas is used). Should your child become ill or gets a cough/cold, please contact our department to see if it is necessary to postpone the appointment. Q: What special instructions should I follow after the sedation appointment? A: Our staff will not discharge your child until the child is alert and ready to go. Children who have been sedated are usually requested to remain at home for the rest of the day with adult supervision. Our staff will discuss specific post-sedation instructions with you, including appropriate diet, physical activity, and requested supervision You will need to make your arrangements for post-operative transport in advance. It is strongly advisable that you bring a second responsible adult with you to assist you with the transport and continuous supervision of you child (specially if you are going to drive your way back) and you should not use public transport to return home. CALDERDALE & KIRKLEES COMMUNITY DENTAL CARE - PCT

Inhalation Sedation – Relative Analgesia Patient Information Leaflet – Sedation in adults

Q: What is inhalation sedation? A: It is a technique that uses a mixture of a sedative gas (called Nitrous Oxide or more commonly ‘Laughing Gas’) and Oxygen to assist the


patient to cope with fear and anxiety and cooperate with dental treatment. The dosages that are administered are very unlikely to cause loss of consciousness. Q: Who could be sedated? A: Best candidates are patients who have a level of anxiety that prevents good coping skills. Inhalation sedation can be very useful when there is gag reflux. It could be also helpful for some special needs adult patients who have limited ability to cope in a cooperative fashion for the delivery of dental care. Q: Why utilize inhalation sedation? A: This form of sedation aids in allowing the patient to cope better with dental treatment and to relieve stress and anxiety reducing thus the need for more advanced pharmacological sedation or general anaesthesia. It is a very helpful tool in the behaviour management of the phobic patient as it helps the desensitization process. The patient does not loose consciousness during treatment being thus able to come in terms with his/her dental phobia and confront his/her fears. It can help to eliminate patient movement promoting thus a better environment for providing dental care. It is also a very valuable aid to control an increased gag reflux. Q: Is Inhalation Sedation safe? A: Careful pre-sedation evaluation is very important. Your dentist will ask you to fill a medical history form prior to your assessment appointment and will discuss with you any particular concerns prior to treatment. Generally speaking dental treatment under Nitrous Oxide inhalation sedation is a safe technique as it provides continuously high levels of oxygen all the way through treatment (at least 30% oxygen is administered when the atmospheric air contains only 21%).In addition the patient’s vital signs are monitored and recorded for the duration of treatment. Your dentist will discuss in more details the risks, the benefits and the alternatives to the Nitrous oxide sedation.


Q: What special instructions should I follow before the sedation appointment? A: In order to alleviate any potential anxiety your dentist may recommend minimal discussion of the dental appointment with other friends or members of family. It is very important to follow the directions of your dentist regarding fasting from fluids and foods prior to the sedation appointment. We recommend that fluids and a light meal should be taken not later than 2 hours prior to the sedation appointment to minimize the risk nausea and vomiting (common side effects when Nitrous Oxide gas is used). Should you become ill or get a cough/cold, please contact our department to see if it is necessary to postpone the appointment. Q: What special instructions should I follow after the sedation appointment? A: Our staff will not discharge you until you are alert and ready to go. Patients who have been sedated are usually requested to remain at home for the rest of the day with adult companionship. Our staff will discuss specific post-sedation instructions with you, including appropriate diet, physical activity, and requested companionship. You will need to make your arrangements for post-operative transport in advance. It is strongly advisable that you bring a second responsible adult with you to assist you with the transport. You should not drive your way back or use public transport to return home.


Appendix V

RA recording sticker


(RA sticker to be attached here))


Appendix VI

Sample of page from clinic book recording the presedation clinic checks


Clinic book to record safety checks prior to sedation

Pre-op sedation checks Contents of all gas cylinders Presence of 1 full oxygen cylinder Correct functioning of controls and flow meters Automatic cut out of Nitrous Oxide No leaks at reservoir bag, cylinder circuit, regulators Pulse oximeter checked

Tick if checked

Name

Date

Comments / Action taken

Signature


Appendix VII

Frequently asked questions


Frequently asked questions A) Equipment for Nitrous oxide/oxygen Inhalation Sedation – general information Dedicated purpose-designed machines for the administration of inhalation sedation for dentistry should be used. Such machines should conform to British Standards and be maintained according to manufacturers' guidance with regular, documented servicing. Scavenging of Waste Gases must be active and sufficient to fully conform to current C.O.S.H.H. standards. Breathing systems should have a separate inspiratory and expiratory limb to allow proper scavenging. Nasal masks should be close fitting providing a good seal without air entrainment valves. (Conscious Sedation in the Provision of Dental Care - Report of an Expert Group on Sedation for Dentistry DOH 2003) Q. What equipment is required for administration of Inhalation Sedation? A. The basic requirement is a purpose-designed Flowmeter, medical gas supply - either an installed pipeline or mobile four cylinder stand with a scavenging system for nitrous oxide. Q. Why do I need to use an Active Scavenger Breathing System? A. C.O.S.H.H. and H & S require that staff is protected from exposure to waste nitrous oxide in the surgery environment. Chronic exposure to nitrous oxide has been linked to occurrences such as spontaneous abortion and reduced fertility. The currently recommended occupational limit of exposure is 100 ppm (parts per million) over an 8-hour TWA (Time Weighted Average). This can only be achieved by use of the following: Active Scavenging (defined as a flow rate of 45 lpm at the nasal hood), Staff rotation and good surgery ventilation or room air changes (recommended 12-15 per hour). A number of active scavenger breathing assemblies are available from different manufacturers. A study published in 2002 stated: "This study compared the effectiveness of three nitrous oxide scavenging systems, the Porter/brown, the Accutron, and the Matrx, in actual time during use in a standardized mock dental treatment protocol that reflected clinical practice while minimizing the influence of confounding variables. At every occasion during the procedure, the Porter/brown scavenger system left the operatory with significantly less nitrous oxide than any of the other scavengers tested. The Porter/brown removed between 71% and 91% of the nitrous oxide compared to the control (no device)." Clinical evaluation of the efficacy of three nitrous oxide scavenging units during dental treatment Certismo, Walton, Hartzell, Farris General Dentistry Sept-Oct 2002

Q. What are the requirements of the equipment regarding the assessment of the gases’ flow and a fail-safe system? The ideal RA equipment must combine the balance of accurate visual flow readings whilst providing safety features all included as standard. It is necessary to allow for


accurate adjustment of gas flow and percentage mixture with the minimum effort from the clinician’s side. It must have a dual seal fail-safe system, which automatically reduces nitrous oxide to zero if oxygen flow fails, providing the patient with ambient air circulation as an immediate alternative, via an entrainment valve.

B) Equipment Maintenance Information

Q. How often should I have my equipment serviced? A. Equipment should be serviced according to original manufacturer recommendation. In the U.K. this usually means one service visit per annum. Frequency of machine use may indicate six monthly service intervals. Medical gas hose assemblies are also inspected for wear or damage. Regulations now state that these should be replaced every four years. Q. Do I need a pipeline check? A. Where the flowmeter head is connected to a medical gas pipeline system it may be subject to variance in operating pressures. Flowmeters can be damaged by unstable regulators delivering incorrect or fluctuating psi. The Engineers carry out a leak and pressure check, also inspecting the regulators for wear or damage. Regulations now state that pressure reducing regulators should be replaced every five years. Q. What are the requirements for medical gas cylinder care and storage? • • • • • • • • • •

Cylinders should be stored in a secure, weather proof, well ventilated area. The cylinders should be secured by means of brackets or chains to prevent toppling. The floor should be level and constructed of concrete or other non-combustible material. The store should have an adequate means of access, to facilitate delivery and collection of cylinders. So far as practicable, lighting and electrical equipment should be sited in a safe position, remote from the cylinder storage. The storage area should be clearly identified i.e. by use of compressed gases warning sign. Lubricants should be avoided. Only lubricants that are made for oxygen service and specified by the equipment supplier should be used. Always use clean hands or gloves when assembling oxygen equipment i.e. when changing cylinders. Medical Gas Pressure Reducing Regulators should be handled with care and replaced every 5 years - sooner if damaged. Separate or identify full and empty cylinders

The above advice is taken in excerpt from the following source: Take Care with Oxygen HSE (Health & Safety Executive) HSE(rev2) Medical Gas Pipeline Systems; Health Technical Memorandum 2022


C) Advice on Cylinder Capacity For Emergency Oxygen Maintaining Standards states that a portable source of oxygen should be available to deal with medical emergencies. This should ideally be capable of delivering a maximum of 15 litres per minute for a minimum of 20 minutes. This indicates use of a ‘D’ size cylinder (pin index fitting) with 340 gaseous litre capacity. If extra capacity is required, then use an ‘E’ size cylinder (pin index fitting) with 680 gaseous litres, although this will require the use of a cylinder trolley.


Appendix VII

Literature references


http://www.kirklees.nhs.uk/uploads/tx_galileodocuments/Inhalation_Sedation_protocol