SAAD National Course in Conscious

Sedation for Dentistry

COURSE HANDBOOK

Society for the Advancement of Anaesthesia in Dentistry

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Introduction The handbook which follows has been produced to complement our National Courses, and so reflect the syllabi set out in current national guidance. We have designed our courses to help provide both dental and medical participants who are ‘new starters’with the necessary knowledge, skills and attitudes ahead of supervised clinical practice with an approved supervisor. This is a mandatory requirement prior to independent clinical practice. The focus of our courses is to ensure that all members of the clinical team are able to deliver safe and effective conscious sedation for their patients who require it, such as those with high levels of anxiety, during potentially unpleasant and distressing surgical procedures or in other situations that might require conscious sedation as an adjunct. The provision of effective pain and anxiety control as part of an agreed and consented treatment plan is a great attribute. In the UK, both the General Dental Council and the Department of Health consider conscious sedation to be an integral and fundamental aspect of the modern practice of dentistry. For those who are already employing sedation in their practice, we hope our courses provide a useful update and stimulus to further advancement. I do hope you will enjoy the course and find this handbook useful. Stephen Jones President of SAAD

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Editors Leah Adams and Zahra Shehabi Acknowledgments The editors would like to thank the SAAD Faculty for their contributions to this handbook.

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Table of Contents

1. Anatomy and physiology 4

2. Principles of pharmacology 10

3. Patient assessment and treatment planning 20

4. Local analgesia: tips and techniques 24

5. Intravenous sedation with midazolam 29

6. Inhalational sedation (Relative Analgesia) 35

7. Monitoring 41

8. Management of sedation related complications 47

9. Paediatric sedation techniques 50

10. Alternative sedation techniques 56

11. Sedation for medically compromised patients 61

12. Psychological approaches 67

13. Legal and ethical issues 74

14. Standards of good practice 80

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1 Anatomy and Physiology Introduction It is important for the sedationist, dental nurses, therapists and hygienists to understand the principles of cardiovascular and respiratory anatomy and physiology in order to appreciate the changes made to these systems by the administration of sedative drugs. CARDIOVASCULAR ANATOMY AND PHYSIOLOGY The circulatory system comprises the: • heart • arteries • arterioles • capillaries • veins

Its main function is to deliver oxygen and other cellular nutrition to the tissues while removing the waste products: carbon dioxide and water. The heart acts as two separate pumps working in parallel. The right heart pumps venous blood to the lungs, where oxygen is taken up and carbon dioxide given up (pulmonary circulation). The left heart pumps blood to the tissues/organs where it gives up oxygen and takes up carbon dioxide (systemic circulation). Coronary circulation The myocardium receives its arterial blood supply via the left and right coronary arteries and their branches. The sinoatrial node (SAN) and atrioventricular node (AVN) are mainly supplied by the right coronary artery (90%), with the remainder supplied by the left circumflex artery. Venous drainage is via the coronary veins which drain into the right atrium. Nerve supply to the heart The heart has an autonomic nerve supply. The sympathetic supply is via cardiac branches of the sympathetic trunk while the parasympathetic supply is via cardiac branches of the vagus nerve. Under resting conditions, the heart is under vagal tone (this reduces the heart rate). Stimulation of the sympathetic system is part of the normal response to fear, producing increased heart rate and force of myocardial contraction.

Average adult resting heart rate = 70-80 beats per minute Average heart rate for a small child = 130 beats per minute

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Tachycardia (defined as a heart rate of > 100/min) and bradycardia (defined as a heart rate of < 60/min) can occur in the absence of pathology e.g. the tachycardia associated with exercise and anxiety; the bradycardia associated with sleep. Electrical conduction system The sinoatrial node (SAN) is the origin of the impulses responsible for normal heart rhythm (‘sinus rhythm’). The atrioventricular node (AVN) regulates the frequency of conduction to the ventricles - the delay in conduction between the SAN and AVN allows the ventricles to fill with blood as they depolarise, prior to ventricular contraction. From here the bundle of His fibres radiate out into the Purkinje network. Heart valves and chambers There are four heart chambers: • right atrium • right ventricle • left atrium • left ventricle

These are separated by four main valves: • Two atrioventricular valves (tricuspid [left heart]; mitral [right heart]) • Two ventricular outflow valves (aortic; pulmonary)

Circulation During systole (atrial and ventricular contraction), blood is pushed through the heart chambers and into the pulmonary and systemic circulation. During diastole the heart muscle is relaxed and the heart fills with blood. Blood returns to the heart from organs and tissues down a pressure gradient with the help of the muscular pump (contraction of calf muscles pushes blood through venous valves) and the respiratory pump (‘bellows’ action of the diaphragm on the inferior vena cava). This venous return is also influenced by other factors such as blood volume and gravity. The circulating blood volume of an adult is 5-6 litres. Cardiac output Cardiac output, the volume of blood circulated in one minute, is approximately 5 litres/min and is dependent on heart rate and stroke volume:

Cardiac Output = Heart Rate x Stroke Volume

Adult stroke volume is approximately 70mls at rest. It is dependent on end-diastolic pressure after the ventricles have filled with blood (preload) and peripheral resistance (afterload). Increased preload causes increased stretch of cardiac muscle fibres which results in increased force of contraction and increased stroke volume (Starling’s Law of the heart). As blood pressure falls, afterload falls so allowing greater shortening of cardiac muscle fibres, greater power of contraction and a corresponding increase in stroke volume. This system is under neuro-endocrine control and is affected by many drugs e.g.most anaesthetic drugs decrease the contractility of heart muscle.

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Heart rate is modified by multiple factors, including: • pain and anxiety • vagal tone • endocrine system, e.g. thyroxine, adrenaline • chemoreceptors (hypoxia and hypercarbia) • baroreceptors (sensitive to fall in blood pressure)

Blood pressure The pressure generated by blood circulating in the major blood vessels is determined by cardiac output and peripheral resistance. ‘Normal’ blood pressure is 120/70 mmHg. In the management of patients with hypertension, the target clinic blood pressure is 140/80 mmHg (diabetic) or 140/85 mmHg (non-diabetic).

Blood Pressure = Cardiac Output x Peripheral Resistance

Blood vessel diameter, particularly small vessels, is controlled by the sympathetic nervous system and circulating catecholamines. An increase in sympathetic activity increases vascular tone while a decrease causes vasodilatation. Factors affecting blood pressure

HYPERTENSION HYPOTENSION obesity drugs (antihypertensives and antianginals) smoking dehydration high salt/fat intake fitness family history normal pregnancy steroids anxiety recent exercise pregnancy (pre-eclampsia)

Arteries, veins and capillaries Arteries carry oxygenated blood from heart to organs in a pulsatile flow. This high-pressure system is a low-volume one, carrying only ~ 20% of circulating blood volume. Veins carry deoxygenated blood back to the heart and are a low-pressure, high-volume system, carrying ~ 75% of circulating blood volume. Gas exchange occurs in the capillary beds.

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RESPIRATORY ANATOMY AND PHYSIOLOGY The respiratory system comprises:

• upper respiratory tract: nose, nasopharynx, larynx • lower respiratory tract: trachea, bronchi • lungs: respiratory bronchioles and alveoli

The lungs have a combined surface area of some 500m2 and are directly open to the outside environment. The acinus (branching respiratory bronchioles and clusters of alveoli) is the unit of gas exchange. Blood flows through a rich capillary network intimately related to the acini, so facilitating gas exchange and ensuring that oxygen enters the bloodstream and carbon dioxide is removed. Optimal gas exchange relies on good ventilation and good perfusion of the lung fields. Inspiration and expiration Inspiration is an active process in which muscle contraction works to enlarge the ribcage. The diaphragm is the main muscle of inspiration, assisted by the intercostal muscles. Expiration, however, is usually a passive process of elastic recoil of the lungs and chest wall. Active expiration involves abdominal muscles, diaphragm and intercostal muscles. Lung capacities and volumes These depend on the size of the lungs and thorax and the degree of inspiratory/expiratory effort.

Tidal volume is the volume of air moved in one normal breath, usually ~ 500mls. Respiratory rate is ~12 breaths per minute for an adult at rest. Minute volume of ~6 litres/min is the volume of air moved in one minute of normal breathing (this is the volume that the flow rate of an inhalation sedation machine must meet for each patient).

Minute Volume = Tidal Volume x Respiratory Rate

Vital capacity ~5 litres is the expiratory reserve volume (to maximum expiration) plus the inspiratory reserve volume (to maximum inspiration). Functional residual capacity ~ 2 litres gives an estimate of oxygen reserve. It allows for breath holding and maintains the pressure of oxygen in the lungs, preventing lung collapse. Dead space volume (~150 mls) is an estimate of the area of the respiratory system which is not available for gas exchange. If a patient is taking very shallow breaths, then tidal volume can < dead space volume, leading to little or no gas exchange. Shallow breathing commonly occurs with CNS depressants such as opioid analgesics and midazolam.

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Composition of air

CONSTITUENT INSPIRED EXPIRED AIR oxygen 20-21% 16%

carbon dioxide 0 4% nitrogen 78% 78%

water vapour yes yes Gas exchange Gas exchange occurs down a diffusion gradient at the alveolar-capillary membrane which is some 0.06mm wide. Exchange rate depends on the concentration gradient as well as ventilation and perfusion ratios. Oxygen is carried in blood almost entirely bound to haemoglobin, an iron-containing protein, each molecule of which has the capacity to carry four oxygen molecules. The haemoglobin molecule changes its stereochemistry with the bonding/debonding of each oxygen molecule. These stereochemical changes affect the affinity of haemoglobin for oxygen and result in the characteristic shape of the oxygen dissociation curve (the curve which represents the relationship between O2 partial pressure in the blood and the % saturation of haemoglobin with oxygen). The curve’s sigmoid shape means that a small drop in alveolar oxygen tension results in a large amount of oxygen being released into the tissues, keeping them maximally oxygenated. Carbon dioxide is carried in solution in blood as bicarbonate ions which dissociate, liberating hydrogen ions. Any changes in CO2 levels will therefore result in pH changes.

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Control of respiration Involuntary control of respiration is based in the respiratory centre within the medulla of the brain. The centre receives signals from chemoreceptors within the brain and major blood vessels, sensitive to rising carbon dioxide concentrations, and from stretch and irritant receptors within the lungs. When chemoreceptors sense an increase in carbon dioxide (changes in blood pH), respiratory drive is increased (rate and depth of breathing). CNS depressants reduce the sensitivity of chemoreceptors. Voluntary control of breathing involves the cerebral cortex sending signals to the muscles of respiration to override the autonomic nervous system. CONCLUSION A knowledge of basic cardio respiratory physiology is essential for the effective and safe practice of conscious sedation.

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2 Principles of Pharmacology

Introduction The safe administration of any drug requires knowledge of its pharmacology. Pharmacology involves consideration of a drug’s pharmacokinetics and pharmacodynamics. Some useful definitions: • Pharmacokinetics – a description of drug absorption, distribution, redistribution, metabolism

and excretion (how the body affects drugs). • Pharmacodynamics – a description of the effects of drugs (how drugs affect the body). • Half-life – the time it takes for the plasma concentration to fall to half its original value.

Complete elimination involves removal of the drug from the receptor sites (sometimes called the redistribution half-life) and then metabolism and excretion (the elimination half-life). Redistribution time is usually shorter than elimination time.

• First-pass metabolism – the portion of a drug which is broken down by the liver on first passage through the portal circulation (applies to orally-administered drugs).

The drugs most commonly used for dental sedation are the benzodiazepines (for oral, intravenous and transmucosal sedation) and nitrous oxide and oxygen (for inhalational sedation). Drugs which produce conscious sedation and analgesia may be administered by a variety of methods. The choice of route depends on the properties of the drug and how quickly a response is required. These include: • Intravenous • Inhalational • Oral • Transmucosal (intranasal/buccal)

Drugs administered parenterally (by injection) or by inhalation are quickly absorbed and usually act quickly. Oral absorption is unpredictable and time-consuming because the rate of gastric emptying is altered by anxiety, disease, other drugs and the presence of food, and drugs are also subject to first-pass metabolism. The transmucosal route can be almost as fast as the parenteral route. It is important to remember that whatever the initial route, all sedative drugs travel to their target sites via the systemic circulation. A consideration of pharmacokinetics and pharmacodynamics is important when choosing the most appropriate drug for each individual patient.

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Pharmacokinetics The degree of protein binding of a drug alters its availability. A portion of the drug dose is dissolved in plasma (the active form) whilst the rest is bound to plasma proteins and is not free to combine with receptor sites. Some disease processes change the proportion of bound drug. Similarly, two drugs can compete for the same binding site and thereby increase the free concentration of one or both agents. Either of these mechanisms may increase or decrease the expected clinical effects. Drugs are eliminated by a variety of routes. Most of the inhalational agents used for sedation are excreted through the lungs. For benzodiazepines, the most important organs are the liver and the kidneys which metabolise and excrete these drugs. The measure of elimination of the drug is the half-life. The properties and route of administration of different drugs determine the speed of absorption and distribution and hence the speed of onset of the sedative effect. A drug with rapid metabolism and excretion produces a swift recovery and earlier discharge for the patient. Pharmacodynamics Pharmacodynamics describes the effect the drug has on the patient and includes both desirable and undesirable effects. The definitions of ‘desirable’ and ‘undesirable’ effects are not fixed but depend upon what one is trying to achieve. Most sedative drugs elicit a response via receptors which are specific to each drug. Receptors are located in cell membranes. All benzodiazepines have a common core structure with individual differences which determine their solubility and precise actions. When drugs bind to receptors in the central nervous system these are altered, and the activity of the cell is either stimulated or inhibited. These drugs are called agonists. Midazolam is a benzodiazepine agonist. Drugs which act to displace agonists from the receptor sites thus terminating their effects are known as antagonists. Flumazenil is a benzodiazepine antagonist. Properties of the ideal sedative drug:

• Comfortable, non-threatening method of administration • Rapid onset • Predictable sedative/anxiolytic action • Controllable duration of action • Analgesic • No side-effects • Rapid and complete recovery

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INTRAVENOUS SEDATION Benzodiazepines The benzodiazepine group of drugs has a number of desirable pharmacodynamic properties which make these agents useful drugs for conscious sedation: These include: • Anxiolysis • Sedation • Muscle relaxation • Anterograde amnesia

For the sedationist, the most significant undesirable property of these drugs is respiratory depression, which is usually easily managed but requires careful monitoring. Although benzodiazepines have the potential to produce dependency, this is not a problem with the use of midazolam for conscious sedation. Diazepam Diazepam produces excellent sedation and was for many years the drug of choice for dental sedation. However, it has a number of disadvantages which have resulted in its being superseded by midazolam. Midazolam Midazolam is currently available as several injectable preparations which are stable in aqueous solution, and is non-irritant on injection. In line with current guidance, SAAD recommends the use of low concentration midazolam, which comes as a 5mg/5ml solution. The higher concentration formulations (10mg/5ml and 10mg/2ml) are not recommended as the risk of midazolam-related incidents is more likely. Midazolam should be titrated, which means administering the drug slowly in small-volume increments whilst assessing the patient’s response. This mode of administration ensures that patients receive an adequate but not excessive dose of the sedative agent. It is impossible to predict the correct sedative dose of intravenous midazolam for any individual patient on the basis of his weight, height, Body Mass Index or the apparent degree of anxiety.

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Properties of midazolam

Water soluble Yes

Solvent Aqueous

Irritant No

Presentation 5mg/5ml, (10 mg/5 ml and 10mg/2ml although not recommnended for routine sedation)

Distribution half-life 6-15 mins

Elimination half-life 1.5-2 hours

Usual dose 2-7.5 mg

Late active metabolites None

Analgesia No

Within the United Kingdom midazolam is available in several formulations. Traditionally, high concentration midazolam (10mg/2ml) was mixed with other liquids for oral use. However, alternatives are available in syrup form (2.5mg/ml) and should be used where advocated. Midazolam may also be administered intranasally via a Mucosal Atomisation Device attached to a 1ml syringe. Between 0.25mls and 0.3mls of 40mg/ml concentration is recommended. However, bolus administration needs to be approached with caution, particularly when treating older patients. Temazepam Temazepam is no longer considered to be the drug of choice as an oral alternative for intravenous or inhalational sedation in the dental surgery. It may, however, have a place in the management of pre-appointment anxiety. For example, temazepam may be prescribed to ensure a satisfactory night’s sleep prior to a dental visit. It has been produced in various forms: tablet, gel-filled capsule, and an elixir for oral administration. The different formulations have different rates of absorption, but temazepam is reasonably rapidly absorbed following oral administration. The sedative effects are usually clinically apparent for at least 45 minutes. Temazepam has a relatively short elimination half-life (5-11 hours) which makes it a useful drug for conscious sedation.

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Flumazenil Flumazenil (Anexate) is a specific benzodiazepine antagonist. It has the same core structure as all other benzodiazepines. However, as it has a stronger affinity for the receptors than most agonists, including midazolam, it will displace them. Flumazenil reverses the anxiolytic, sedative and respiratory depressant effects of midazolam but has no clinically apparent sedative or stimulant effects. It does not reverse the anterograde amnesia induced by midazolam. Therefore, the loss of memory of unpleasant events which took place before reversal with flumazenil is retained. Flumazenil is used for the emergency reversal of sedation but can be used electively in selective cases (e.g. patients with learning disabilities or mobility problems). Reasons for its use must be justified and recorded. Flumazenil has a shorter half-life than midazolam. However, ‘re-sedation’ is not a clinical problem as the cessation of action of flumazenil (approximately 50 minutes) coincides with the point at which patients would normally be expected to be fit for discharge. Allergy to the benzodiazepines is rare. Mechanism of action of benzodiazepines Benzodiazepines act throughout the central nervous system. Specific benzodiazepine receptors are located on nerve cells within the brain. All benzodiazepine molecules have a common core shape, which enables them to attach to these receptors. The effect of attaching benzodiazepines to cell membrane receptors is to alter an existing physiological 'filter'. The normal passage of information from the peripheral senses to the brain is filtered by the GABA system. GABA (gamma-amino-butyric acid) is an inhibitory neurotransmitter which is released from sensory nerve endings as a result of nerve stimuli passing from neurone to neurone. When released, GABA attaches to receptors on the cell membrane of the post-synaptic neurone. This stabilises the neurone by increasing the threshold for firing. In this way, the number of sensory messages perceived by the brain is reduced. Benzodiazepine receptors are located on cell membranes close to GABA receptors. The effect of having a benzodiazepine in place on a receptor is to prolong the effect of GABA. This further reduces the number of stimuli reaching the higher centres and produces pharmacological sedation, anxiolysis, amnesia, muscle relaxation and anticonvulsant effects. All benzodiazepines, which are central nervous system depressants, have a similar shape with a ring structure on the same position of the diazepine part of each molecule. By contrast, flumazenil, the benzodiazepine antagonist, does not have this ring structure and has a neutral effect on the workings of the GABA system. Flumazenil is an effective antagonist, as it has a greater affinity for the benzodiazepine receptor than the active drugs and therefore displaces them. Metabolism of benzodiazepines takes place in the liver. Midazolam has no metabolites which are active once the parent drug has been removed. The water-soluble metabolites of the benzodiazepines are excreted via the kidneys.

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The anterograde amnesia produced is a desirable effect in terms of reducing the patient’s memory of treatment but, paradoxically, is less helpful when trying to ‘wean’ patients away from treatment under sedation. The most profound amnesia occurs immediately after induction, but some disturbance to short-term memory may persist for several hours or even until the following day. The muscle relaxant effect of benzodiazepines contributes to the difficulty in standing, walking and maintaining balance experienced by many patients following treatment. Respiratory effects of benzodiazepines Benzodiazepines produce respiratory depression. This is usually mild in healthy patients if the drug is administered intravenously by slow titration. It can, however, be a significant problem in unwell or elderly people. Even in a fit, healthy individual, a fast injection or a large quantity of midazolam has the potential to depress respiration to the point of apnoea. There are two mechanisms by which ventilation is depressed. First, relaxation of the muscles of respiration causes a dose-related reduction in the rate and depth of breathing. Second, the reduction in sensitivity of the central carbon dioxide and oxygen chemoreceptors decreases the ability of the respiratory centre to increase the respiratory drive in the presence of hypercarbia and/or hypoxia. Benzodiazepine-induced respiratory depression affects all patients who are sedated with these drugs by any route of administration. For this reason, it is important to monitor respiration and oxygen saturation levels throughout sedation, particularly with intravenous sedation, but also after the oral or transmucosal administration of benzodiazepines. Cardiovascular effects of benzodiazepines Benzodiazepines have few significant effects in healthy people. There is a decrease in mean arterial pressure, cardiac output, stroke volume and systemic vascular resistance. This may present as a small fall in arterial blood pressure immediately following induction of sedation. However, this is normally compensated by the baroreceptor reflex and is of negligible clinical significance, except in people with compromising cardiovascular disease. Propofol Propofol (Diprivan 1%) is a synthetic phenol anaesthetic induction agent which was introduced into clinical use in the 1980s. It is extremely lipid soluble but virtually insoluble in water. Each 20ml ampoule contains 200mg of propofol (10mg/ml). The solution is sometimes painful on injection particularly when a small vein is used. The pharmacokinetics of propofol make it an ideal agent for certain dental procedures. The redistribution half-life is approximately two to four minutes. In order to maintain sedation at a constant level, it is therefore necessary to administer propofol by continuous infusion. Metabolism takes place in the liver and metabolites of propofol are excreted by the kidneys. The elimination half-life is about 60 minutes in fit patients.

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Propofol is very useful for short procedures when sedation is required for only a few minutes, for example, in the extraction of a single tooth. Recovery occurs rapidly after the drug is discontinued. It may also be used for longer cases, particularly when only light sedation is required. Propofol tends to depress respiration. The frequency of hypersensitivity reaction is similar to that of other anaesthetic induction agents. As its margin of safety is narrower than midazolam, propofol should be used only by those trained in advanced sedation techniques. Opioids For some patients, the use of a single agent does not provide an adequate degree of sedation to enable treatment to be provided. In these cases, a combination of agents may make treatment possible, thereby avoiding the need for general anaesthesia. The most frequently used combination of agents is an opioid and midazolam. Individual opioids, like benzodiazepines, act through CNS receptors and have either agonist or antagonistic actions. These drugs produce a number of therapeutic effects including analgesia, sedation and euphoria. Their undesirable effects include cardiorespiratory depression and nausea and vomiting. The most important of these in relation to conscious sedation is respiratory depression. Great care must always be taken when a combination of an opioid and a benzodiazepine is used for sedation. If an opioid is used for sedation, the opioid antagonist naloxone (Narcan) must be available. Naloxone is a pure opioid antagonist and reverses respiratory depression, analgesia and sedation.

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INHALATIONAL SEDATION Inhalational agents are commonly used for dental sedation. Traditionally nitrous oxide has been the only gas used. Volatile anaesthetic agents are now being investigated and may have a role to play in the future. Nitrous oxide Nitrous oxide is rapidly absorbed. The rate of absorption depends on a number of factors including the solubility of the drug in blood. Agents with a low solubility produce a rapid onset of sedation because the concentration of the drug in the blood, and therefore in the brain, rapidly equilibrates with the inspired concentration. When the agent is discontinued, recovery occurs quickly as the concentration of the agent falls. The Minimum Alveolar Concentration (MAC) is a value (obtained experimentally) which represents the potency of an inhalational agent. Nitrous oxide has a high MAC, in contrast with most volatile anaesthetic agents. A high MAC indicates an agent of low potency, which is ideal for conscious sedation. In the UK, nitrous oxide is supplied in blue cylinders containing both gaseous and liquid phases under high pressure (5400 kPa or 800 psi). Properties of nitrous oxide

Induction/recovery Rapid and smooth

Potency (MAC) Weak (105%)

Blood gas solubility Low (0.47)

Metabolism

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Planes of Relative Analgesia

Plane I Moderate sedation and analgesia. Usually obtained with concentrations of 5-25% N2O

Plane II Dissociation sedation and analgesia 20-55% N2O

Plane III Total analgesia 50-70% N2O Planes I and II are clinically useful for dental sedation but plane III is generally considered to be too close to general anaesthesia to be safe. The low solubility of nitrous oxide in blood and tissues results in a rapid outflow of nitrous oxide across the alveolar membrane when the incoming gas flow is stopped. This reduces the percentage of alveolar oxygen available for uptake by up to 50%. This phenomenon, diffusion hypoxia, may be counteracted by giving 100% oxygen for two minutes at the end of the procedure. Long-term occupational (or recreational) exposure to nitrous oxide is an area of increasing concern. Biochemical, haematological, neurological and reproductive side-effects have been reported. Nitrous oxide produces reversible inhibition of the enzyme methionine synthetase which is involved in the synthesis of vitamin B12. Clinically significant bone marrow depression can be detected after as little as six hours' exposure to 60% nitrous oxide (or after much lower percentages for much longer periods of time). Nitrous oxide has also been linked to an increase in the rate of miscarriage among dentists and dental nurses. Effective waste gas scavenging (active scavenging at 45 l/m) appears to reduce the risks and daily exposure to very low concentrations (

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Sevoflurane Sevoflurane is a fluorinated derivative of methyl isopropyl ether which was first synthesised in the early 1970s. Sevoflurane has a MAC of 2% and a low blood gas solubility (0.6). These physical characteristics make sevoflurane a potent anaesthetic agent with rapid uptake and speedy recovery. It is used extensively in day case surgery where rapid recovery is important. It is pleasant to inhale, non-irritant and non-pungent. The properties that make sevoflurane a useful anaesthetic agent also make it a promising sedation agent. However, a specially calibrated vaporiser is required in order to titrate low concentrations of sevoflurane (up to 1%) in oxygen (or nitrous oxide and oxygen). Sevoflurane is partly metabolised (5%) and so some care is required in people with severe liver or kidney disease. At present, sevoflurane is not widely used for dental sedation because of the practical problems associated with attaching a vaporiser to any of the currently available inhalational sedation machines. CONCLUSION When selecting drugs, it is important to know and understand their clinical effects. This is the key to safe, effective conscious sedation.

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3 Patient Assessment and Treatment Planning Introduction A satisfactory first visit is crucial to the success of subsequent treatment under sedation. There is a great deal of information to be acquired from the patient. At the same time, it should never be forgotten that the patient is assessing the operator too! The first meeting should ideally be out of the surgery environment (although this is not often possible) and in the nature of an informal “chat”. Assessment should be done at a separate appointment but may need to be just prior to treatment if there is a need for urgent intervention. The following points need to be covered: Find out the problem It is often helpful to get the patient to complete a questionnaire asking the nature of their fears (see below). It breaks the ice, and other questions may be included so as to assist in steering the conversation in the right direction. A discussion of the reasons for being frightened of dentistry can be lengthy and occasionally upsetting. Be positive and try not to dwell on the unpleasant past. Criticism of previous dentists should be listened to but not necessarily acknowledged. Needle phobia is a common condition that requires some elaboration regarding patients’ acceptance of venepuncture. The use of the Modified Dental Anxiety Scale (MDAS) can also be a useful tool to gauge the level of dental anxiety (Appendix 1). This questionnaire forms part of the Index of Sedation Need (IOSN) – a toolkit that can be used to help justify the use of sedation. Medical history A full medical history should be taken in the same way as for all patients. From the sedation point of view, special note should be made of respiratory and cardiovascular problems, liver and kidney disease, psychiatric disorders and pregnancy. Drugs regularly taken can alert the operator to undisclosed conditions and raise the possibility of potential drug interactions. Some medicines can potentiate the effect of sedation drugs. Special note should be made of CNS depressants (including benzodiazepines), and antihypertensives (e.g. beta-blockers). The use of recreational drugs, including alcohol, tobacco and cannabis, should be enquired into. In some cases, it may be advisable to discuss the patient’s medical history with the General Medical Practitioner or hospital consultant. The ASA classification may be helpful in determining suitability of patients undergoing conscious sedation. Generally speaking, patients who are ASA I and II are suitable for treatment in primary care. More complex patients may need to be referred to community or hospital settings.

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Dental history The patient’s experiences at the dentist over the years are important. We need to discover:

• Whether they were able to have normal dentistry in the past

• When they first became fearful of dentistry, and what provoked the fear

• When they last visited the dentist

• Whether they have had sedation before

• What concerns them most about their teeth

• Whether they are having symptoms from teeth

Social factors The patient’s domestic circumstances are relevant, as an escort is going to be required for sedation appointments. In addition, responsibilities such as children or elderly parents may make it difficult for some patients to attend and to recover safely at home. It should be emphasised that escorts must be able and reliable enough to care for the patient for the entire period of home recovery. Examination Whilst some patients will allow a full intra-oral examination, the operator may have to be content with a visual examination only (no probe or blowing on the teeth). For a very few patients, intra-oral radiographs may have to be postponed until a later date when the patient is sedated. Panoral techniques are usually accepted and can give valuable information at this early stage. Discussion Once a preliminary treatment plan has been established, the following treatment options can be discussed with the patient:

• LA alone

• Cognitive Behavioural Therapy

• Inhalation sedation

• Intravenous sedation

• Oral or transmucosal sedation

• Combinations of the above

• GA

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A description of the types of sedation available should then follow. The reaction from the patient at this stage is important in deciding which sedation technique is most appropriate. The simplest technique which will enable treatment to be carried out, is generally the best. Finally, as part of your pre-operative checks;

• Record:

o Blood pressure

o Oxygen saturations

o Respiratory rate

o Heart rate

o BMI

• Examine veins (if appropriate).

• Get consent form signed (consent to include discussion of benefits, risks, and alternative options).

• Give written and verbal instructions for both patient and escort (see below).

• In general practice, a written provisional treatment plan with fees should be given to the patient.

• Make appointment.

Treatment planning A preliminary treatment plan may have to be significantly altered once the degree of cooperation has been ascertained after the first sedation appointment. In addition, the patient’s oral hygiene and dental aspirations may improve once treatment is under way and the patient realises that dentistry is possible after all! It is best not to promise advanced restorative procedures until after the first sedation visit. The first visit should be one of confidence building. Choose a procedure that is achievable, of considerable benefit to the patient (relief of pain or restoration of appearance), and predictable. It may be desirable to prescribe GA for some procedures (e.g. surgical removal of teeth that are not restorable) and to complete restorative treatment with sedation. In these cases, it may be preferable to provide initial treatment with sedation to find out level of cooperation as this may alter the treatment plan for GA. Some patients may prefer inhalation sedation for fillings and intravenous sedation for extractions.

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Patient management Remember that patients selected for either inhalational sedation (IS) or intravenous sedation are more than usually anxious about dental treatment and may also have specific fears (e.g. the dental drill, pain, injections, loss of self-control). All the procedures must therefore be carried out in a particularly careful and considerate manner, e.g. reassuring explanations and the use of topical analgesia before the administration of LA. Remember, too, that in most children and in many adults, sedation (especially IS) may be used to facilitate behaviour modification so that the patients can learn to overcome their fears and phobias. Sedation should never be allowed to take the place of good patient management and satisfactory pain control. Instructions Before sedation: on the day of treatment

• Take your routine medicines at the usual times

• Have only light meals and non-alcoholic drinks (up to two hours before your appointment)

• Bring a responsible adult with you to the surgery to escort you home and care for you afterwards

After sedation: until the following day

• Do not travel alone – travel home with your escort, by car if possible

• Do not drive or ride a bicycle

• Do not operate machinery

• Do not drink alcohol

• Do not return to work or sign legal documents

• Do not look after young children or adults who require personal care

• Avoid internet use

CONCLUSION

Patient assessment can be the most challenging part of providing a sedation service. Carrying out the assessment in a structured way at a separate appointment is more likely to be successful. Planning dental care under sedation requires a different approach from treatment under local anaesthesia for a non-anxious person.

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4 Local Analgesia: Tips and Techniques Introduction The success of conscious sedation depends on the success of local anaesthesia. This section of the course aims to provide some tips that will help the successful use of conscious sedation rather than turn the participant into an expert in local anaesthesia. Pain and anxiety are interrelated. Anxiety influences the perception of pain, and painful experiences can increase anxiety. Many patients will give a history of a painful experience as provoking anxiety. Commonly reported problems are related to failure of local anaesthesia and intravascular injection. More sedation appointments will fail as a result of inadequate local anaesthesia than as a result of inadequate sedation. LOCAL ANAESTHETIC TECHNIQUES IN SEDATED PATIENTS When to give the LA? This surprising question is frequently asked. Fear of injections is one of the most common anxieties in dentistry. The local anaesthetic is given when the patient is sedated and ready for treatment. It is possible to test for the efficacy of local anaesthesia on a sedated patient. The use of topical LA Patients who are sedated with midazolam will often react to painful stimuli in a more extreme manner than “normal” patients. This can result in hyperactivity, crying or movements away from the painful stimulus. It is beneficial to give local anaesthetic injections as painlessly as possible. The use of topical anaesthesia is an effective way of reducing the pain of local anaesthetic injections. The following are available for use in dentistry: • Lidocaine 2% gel • Lidocaine 5% ointment Lidocaine 10% spray • Benzocaine 20% gel

The benzocaine topical has two main advantages:

1. It is more rapidly effective 2. It is poorly absorbed into the systemic circulation, and thus does not contribute to systemic

toxicity Choice of local anaesthetic The gold standard is still lidocaine with epinephrine (adrenaline) as the vasoconstrictor • Lidocaine 2% with 1:80,000 epinephrine Effective in 2-3 minutes (infiltration) Duration approximately 45-60 minutes

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Maximum dose 4.4mg/kg up to 300mg absolute maximum • Prilocaine 3% with 0.03 IU/ml felypressin

Slower onset than lidocaine Similar duration of action Maximum dose 6mg/kg up to maximum of 400mg

• Mepivacaine 3% plain or 2% with 1:80,000 epinephrine

Causes least vasoconstriction so can be used plain Duration of action 30 minutes More effective for block than infiltration Maximum dose 4.4mg/kg up to 300mg absolute maximum

• Articaine 4% with 1: 100,000 or 1:200,000 epinephrine

Short half-life due to metabolism in plasma Serial use has lower toxicity than other agents Although non-surgical paraesthesia with inferior alveolar nerve blocks (IANBs) has been reported, there is evidence that these can also be produced by other local anaesthetic solutions. Opinion is divided as to whether there is an issue administering IANBs. Evidence of greater efficacy of articaine is just starting to emerge to support the clinical impression that it is more effective for infiltration over upper incisors and as an adjunct to IANBs when used as a buccal infiltration. Maximum dose 7mg/kg

Techniques of local anaesthesia under sedation Anaesthesia is achieved in the same way as if the patient was not sedated. If a patient would require LA for treatment if they were not sedated, then they will also require LA for the same treatment under sedation. Any number of quadrants, can be anaesthetised , provided this stays within the maximum dose of LA. Can use bilateral IAN Blocks • Unpleasant for the patient post-operatively • No risk of airway problems (posterior third of tongue has different innervation) • Allows decreased number of visits (removal of all four wisdom teeth in one visit) • Use can be reduced by using incisive (mental) nerve block when indicated • Intraligamentary LA particularly useful for extractions under inhalation sedation • Can cause postoperative pain when used for restorative treatment • Success is tooth-dependent

Does inhalation sedation provide enough anaesthesia to allow dental treatment? Nitrous oxide is a good analgesic, particularly for ischaemic muscle pain. It is less effective for the control of operative pain.

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Overdose of nitrous oxide is unpleasant, and thus increasing the amount of nitrous oxide used to try and avoid the use of local anaesthesia should be approached with great caution. Testing efficacy of local anaesthesia It is possible to test for the efficacy of local anaesthesia on sedated patients. Patients are also able to distinguish differences between sides (for example where an IAN Block has been given). Local anaesthetic toxicity The best management for local anaesthetic toxicity is prevention. The best way of preventing toxicity is to stick to the maximum safe doses, remembering that the toxic effect of different local anaesthetics is an additive effect. Thus if 50% of the maximum dose of lidocaine is used and the operator wishes to add another local anaesthetic, they can only use 50% of the maximum dose of the second agent. Toxicity can also be caused by a relative overdose if a large bolus of local anaesthetic enters the bloodstream. This is usually caused by an intravascular injection. This is best prevented by the use of syringes capable of aspiration for all injections. Other considerations The amnesia produced by benzodiazepine sedation means that patients are unlikely to remember the administration of local anaesthesia. This coupled with the fact that many of the patients have little experience of dental treatment means that there is a greater need to warn patients regarding the effects of local anaesthesia and in particular the hazard of lip biting whilst still under the influence of benzodiazepines. TOPICAL SKIN PREPARATIONS There are two preparations available for topical skin anaesthesia to reduce the discomfort of intravenous cannulation. EMLA Eutectic mixture of local anaesthetics. This preparation contains 2.5% lidocaine and 2.5% prilocaine. Onset of acceptable anaesthesia takes 60 minutes under an occlusive dressing. Side-effects: - profound vasoconstriction. Ametop Amethocaine gel. This is an ester-type local anaesthetic. Onset of acceptable anaesthesia takes 45 minutes under an occlusive dressing. Side-effects: - skin reactions are common. Many patients have erythematous reactions, particularly if the preparation is on for longer than 45 minutes.

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Clinical use Both preparations provide good topical anaesthesia of the skin. In clinical practice, they are probably more useful in children than adults. In adults the anxiety regarding cannulation is more about the process rather than the pain, and adults are less easy to distract. In children, effective distraction can be achieved if the topical anaesthetic is placed on both hands and the occlusive dressing is removed from the second hand as the first is cannulated. If topical skin anaesthesia is used regardless of which preparation is used, the author would advocate that the patients are taught to apply the gel and dressing so that excessive waiting in the dental environment is avoided. An alternative is to use inhalation sedation with nitrous oxide. This has the advantage that in addition to analgesia, anxiolysis and vasodilation are produced. USEFUL ADJUNCTS Oraqix This product is a periodontal gel containing 2.5% lidocaine and 2.5% prilocaine. These are the same active agents as in EMLA. Oraqix is a thermosetting preparation designed to be used in periodontal pockets. It produces anaesthesia of the gingival tissue. There is sufficient anaesthesia to allow probing and scaling and root planing. The use of Oraqix can allow some needle-phobic patients to undergo nonsurgical periodontal treatment without recourse to conscious sedation. If used in combination with conventional local anaesthesia, the dose of Oraqix must be included in the calculation of the maximum permissible dose. • Oraqix is a non-injectable dental local anaesthetic indicated in adults for localised

anaesthesia in periodontal pockets for diagnostic and treatment procedures • Oraqix was launched in the UK in November 2005.

Computer controlled LA delivery systems There are two computer-controlled LA delivery systems – the Wand and the C Syringe. Both have the advantage of controlled pressure of delivery resulting in a more comfortable experience for the patient. There are new techniques of LA administration possible with these devices, which reduce the amount of local anaesthetic required and the amount of soft tissue anaesthesia produced. Detailed descriptions of these techniques are beyond the scope of this course. The Safety Plus system This is a system that removes the need to re-sheath LA needles. In theory this reduces the incidence of needle stick injuries. This system is being increasingly adopted in dental schools and primary care settings.

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CONCLUSION Effective local anaesthesia is of fundamental importance to the practice of conscious sedation in dentistry. More sedations probably fail as a result of poor LA than any other factor. An understanding of the maximum safe dose of LA which can be used allows the maximum benefit to be achieved at each sedation appointment. Local anaesthesia is still an advancing area.

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5 Intravenous Sedation with Midazolam Midazolam is almost the ideal drug for dental sedation. Advantages of IV sedation with midazolam: • Rapid onset (five minutes or less) • Good patient co-operation • Good amnesia • Reasonably wide safety margin

Disadvantages of IV sedation with midazolam: • No clinically useful analgesia • Respiratory depression • Occasional disinhibition effects • Post-operative supervision for a minimum of eight hours is required • Elderly patients are easily over-sedated

INDICATIONS AND CONTRA-INDICATIONS Indications: • Moderate to severe anxiety in adults and children • Unpleasant procedures e.g. oral surgery • Medically compromised patients e.g. angina • Hypersensitive gag reflexes • Patients with learning disabilities and challenging behaviour • When other sedation methods are contra-indicated • As an alternative to GA

Contraindications: The only absolute contraindication to the use of midazolam is allergy to any benzodiazepine. Fortunately, this is very rare. In the following circumstances care and caution are needed: • Pregnancy and during breast-feeding. Midazolam should not be administered to a pregnant

patient due to its effects on the unborn child. It is also excreted in breast milk so if a breast-feeding mother requires IV sedation she should not feed her child for eight hours post-sedation

• Severe psychiatric disease, alcohol or drug abuse. The effects of IV sedation are unpredictable in people with mental health disorders or those accustomed to high levels of alcohol or illicit drugs. While they can be sedated these are not suitable patients for the inexperienced sedationist

• Impairment of hepatic or renal function. People with reduced liver and kidney performance may take longer to metabolise and excrete midazolam

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• Needle phobia. Here the success of treatment depends on the degree of phobia. Some

patients may be able to accept cannulation with the application of topical anaesthetic cream (EMLA or Ametop) and / or nitrous oxide. Other more extreme phobias may require administration of midazolam orally or intra-nasally followed by cannulation.

• Doubts about the ability to provide a suitable escort. A sedated patient must be taken home by a suitable escort who can stay with the patient until the evening. A patient cannot be sent home alone even by taxi. If they cannot provide an escort, then IV sedation cannot be offered. Most people faced with this ultimatum will find someone to accompany them. If not, alternative treatment options need to be considered

Patient checks before sedation On arrival the receptionist should ensure that a suitable escort is present. If the patient is known to the practice, then it may be acceptable to have a contact number to call the escort at discharge time. In other settings, it is better to ensure the escort is present before beginning sedation and ask them to wait. The medical history and consent should be confirmed and pre-operative checks recorded – blood pressure, oxygen saturations, heart rate and respiratory rate. It is not necessary to starve before single drug IV sedation but for their comfort it is wise that the patient avoids eating for up to two hours before the appointment. Some sedationists like to give a glucose drink to patients who have starved. Different practitioners have different approaches to alcohol before sedation. While it would be ill-advised to sedate someone who is drunk, some patients need the help of alcohol to reduce their anxiety before dentistry. Patients should also be asked to visit the lavatory before treatment. Equipment These drugs and equipment should be made ready before the patient enters the surgery.

• Midazolam (5mg in 5ml) • Flumazenil • Safety cannula • 5 or 10 ml syringe for midazolam • Midazolam label • Blunt 21g drawing-up needle • Saline • Separate syringe for saline • Saline label

• Alcohol wipe • Adhesive to secure cannula • Tourniquet • Pulse oximeter • Means of recording blood pressure • Oxygen and nasal cannula • Cotton wool roll • Plaster

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Cannulation Novice sedationists are often anxious about achieving venous access. It is a skill which develops with time and although a description and practical advice are given here it does require lots of practice. Any reasonably large vein can be used. Those most commonly used are the cephalic or median cephalic veins of the ante-cubital fossa and the superficial metacarpal veins of the dorsum of the hand. In situations where no veins can be palpated, the dorsum of the feet may be used. Experienced operators often have a preferred site as will some patients. A tourniquet can be used to occlude venous return and make veins more prominent but it is sometimes more pleasant if an assistant maintains a steady grip around the limb, proximal to the intended point of cannulation. It also reduces the chance of the patient moving as the needle approaches. Pressure must be firm enough to prevent venous return but must not occlude the arterial supply. The venepuncture site must be below the level of the heart in order to encourage venous pooling. Patients who are cold and frightened may appear to have no veins. Gentle tapping over the site of the vein or placing the patient's hands in warm water can help. As a last resort, a sphygmomanometer cuff, inflated to a pressure between systolic and diastolic blood pressures can be used. It is worth taking time to locate a good vein, checking all four sites if necessary before selecting the best one. The use of inhalation sedation with nitrous oxide can help increase vasodilation and hence cannulation. Most operators use a small, or a dual port IV catheter system such as BD Nexiva (20 - 24 g) safety cannula. Butterfly needles are no longer considered appropriate as the lumen rapidly becomes occluded by clotted blood thus making the administration of emergency drugs difficult or impossible. Butterfly needles also have a habit of ‘cutting out’ of the vein. While injecting the drug, the patient should be asked if any discomfort is felt. Also, care should be taken to ensure that the cannula remains within the vein during administration by securing it with non-allergenic tape. Saline can be used to flush through the cannula and check correct siting. Method of administration Induction should be carried out with the patient lying supine. The pulse oximeter should be in place before induction and the reading noted. Supplementary oxygen and nasal cannulae must be available for use and, for some medically compromised people, should be in place before induction eg patients with angina. It is not possible to determine the correct dose of midazolam on the basis of the patient's body weight or age and a titration technique is required. The dose will also vary for the same patient on different occasions.

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The following regimen is appropriate for most fit adult patients: • 2 mg of midazolam over 30 seconds • Wait 90 seconds and observe the effect • Increments of 1 mg midazolam are then given at 30 second intervals until adequate sedation

is achieved. Care should be employed when sedating older people (>65) – think about both chronological and biological age. There is reduced plasma protein binding of drugs meaning that there is more free drug available to cause a sedative effect. The regime above should be adjusted in the elderly:

• 1mg of midazolam • Wait four minutes to allow a longer circulation time • Additional increments of 0.5mg every two minutes

Some older patients are adequately sedated on as little as 2mg of midazolam. Signs of sedation There is no specific end point to determine when a suitable sedation level has been achieved but the following are good indicators: • General muscle relaxation • Relief of anxiety • Drowsiness • Slurred speech • Slowed responses • Decreased motor coordination

It is an overall clinical impression, but another useful sign is how well the patient accepts the injection of local anaesthesia. Verbal contact must be maintained throughout treatment. Maintenance of sedation Sedation usually lasts for 20-30 minutes but may be prolonged by further small increments of midazolam (e.g. 1 mg) titrated against the patient's response. This is particularly useful for long cases such as implant surgery when small increments can be given every 10 minutes or so. If a patient ceases to respond to verbal command, treatment must be stopped immediately, the chair made horizontal and the patient's breathing supported until verbal contact returns. Loss of verbal contact means loss of consciousness, a potentially serious situation which requires maintenance of the airway and administering positive pressure ventilation with oxygen via a self-inflating bag. It should never happen when sedation is induced carefully using the method of titration described above with strict adherence to the intervals between increments. In case the patient experiences a sexual fantasy, it is essential that a dental nurse or other chaperone is present at all times during the period of sedation and recovery.

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Reversal of midazolam sedation Flumazenil reverses the sedative, cardiovascular and respiratory depressant effects but not the amnesic effects of midazolam. Flumazenil has a shorter half-life than midazolam. In spite of this, clinically significant re-sedation does not occur when midazolam is used for short clinical procedures. Elective reversal with flumazenil may occasionally be indicated for individuals who take longer than normal to recover, for a patient who has a difficult journey home or for a patient who has mobility difficulties. It should not be used routinely to reverse patients. At the end of treatment When treatment is completed, the patient must be kept under observation and monitored either in the surgery or in a properly equipped recovery area, until able to stand and walk without assistance. The recovery area should be separate from the waiting area and have somewhere for the escort to stay with the patient, as well as appropriate monitoring equipment, including; pulse oximeter, blood pressure monitor, oxygen, portable suction and a recovery chair /bed capable of going into a head tilt position if required. Discharge For the majority of patients, it is usual to wait at least one hour after the last increment of drug was administered before assessing the patient for discharge. However, discharge must be based on an individual patient assessment. Discharge criteria include:

• walking without assistance • oxygen saturations returned to baseline • blood pressure back to near baseline • speech no longer slurred

Patients must only be discharged into the care of an escort, who must be given written and verbal instructions. Although the dental nurse may give postoperative advice it is the dentist’s responsibility to ensure the patient is fit for discharge and meets discharge criteria. The cannula should be removed just before discharge, not at the end of the procedure. Pressure should be applied to the injection site to avoid a bruise. Multiple drug sedation For a few patients, single drug sedation does not provide sufficient cooperation and it is not possible to provide dental care. For these people multiple drug sedation may be considered. Using additional drugs such as opioids can increase the depth of sedation but also increases the risk of respiratory depression. Alternative drugs like propofol may provide better sedation for some patients. The use of these alternative techniques requires the practitioner to have suitable training and experience. Further description of the available drugs is covered in Chapter 10.

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CONCLUSION Intravenous sedation is safe, effective and easy to administer for the majority of anxious patients.

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6 Inhalational Sedation (IS) Aka Relative Analgesia (RA) PROPERTIES AND PRESENTATION OF NITROUS OXIDE • A non-irritant, virtually odourless and colourless gas • A weak anaesthetic with a MAC of 105% • It is heavier than air • Produces anxiolysis, mood alteration, muscle relaxation and analgesia with little amnesia • Suppresses gagging but does not abolish protective reflexes like coughing • Has little in the way of side-effects in therapeutic doses • Is easily administered, rapidly acting and eliminated • Is suitable for all age groups • Has a wide margin of safety • Presented in blue cylinders compressed at 800 lb/in2 (43.5 bar) • Compressed, it is a liquid within the cylinders and sublimates to a gas on delivery

INDICATIONS AND CONTRA-INDICATIONS Indications • Mild to moderate anxiety in adults and children • Unpleasant procedures in patients with low treatment experience • Medically compromised patients • Needle phobia • Gag reflexes • When other sedation methods are contra-indicated • As an alternative to GA (e.g. orthodontic extractions)

Absolute contra-indications • Acute and chronic nasal obstruction • First trimester of pregnancy • Inability to co-operate or understand – age or disability • Where the nasal hood and tubing makes it impossible to access the operating site/field

Relative contra-indications • Inability to breathe nasally with open mouth • Severe chronic obstructive airways disease – cyanosis at rest where respiratory drive may be

dependent on low blood oxygen tension • Nasal or facial deformity

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• Severe forms of medical conditions like Motor Neurone Disease, Parkinson's Disease, Myasthenia Gravis and Multiple Sclerosis

• Severe psychological disorders and nasal hood phobia • Recent ocular surgery (due to risk of mild rise in intraocular pressure during IS) • B12 deficiency • Caution with patients on methotrexate therapy

Requirements The properties of nitrous oxide and its sedation technique easily conform to the definition of conscious sedation for dentistry. Inhalation sedation requires almost all the same medico-legal requirements as intravenous sedation, with the exception of the issue of escorts. Strictly speaking an escort is not an absolute requirement but the clinician needs to carefully assess whether one is required depending on the patient’s circumstances. Clinicians must have: • Undergraduate and/or postgraduate training and trained second appropriate person • Written, informed consent • Specific sedation assessment • Specific sedation contemporaneous record-keeping • Discharge criteria with written pre- and post-operative instructions • Health and safety requirements

ADVANTAGES AND DISADVANTAGES OF INHALATION SEDATION Advantages • It is a non-invasive, simple technique (no extra needles for the patient) • It is suitable for all age groups • It has a rapid onset and the drug level is easily adjusted • It has few side-effects and sedation is easily discontinued • It is entirely excreted via the lungs, so recovery is rapid • No fasting is required • It provides some analgesia – generally soft tissue (not hard tissue) • It is very useful in patients with hypersensitive gag reflexes • Non-addictive • Useful for long procedures as the sedation is constantly supplied throughout

Disadvantages • It may not be suitable for severe anxiety • There is a degree of ‘technique dependence’ that requires psychological support • The amnesia is variable • Route of administration close to operating site • Nitrous oxide pollution risks

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• Initial equipment set-up and maintenance costs • May cause nausea/vomiting at high doses

Equipment There is a wide range of dedicated inhalation sedation equipment available from several suppliers. • Piped or portable systems are available dependent on funds. Portables approx. £3600 + • Active scavenging systems are recommended • Plan the service costs into the financial assessment • Health and safety issues re: bottle carriage, storage and COSHH documentation • Peripheral costs include nasal hoods and tubing dependent on whether reusable or disposable

systems are chosen All portable systems are similar in that they contain a bottle-carrying device with a gas delivery head attached. The head contains the pressure-reducing valves and must be serviced annually. Each head unit has a flow dial and flow meter tubes for oxygen and nitrous oxide, mixture dial, air entrainment valve, oxygen flush button, pressure gauges and common gas outlet. Tubing and nasal hood systems vary dependent on the type of scavenging used. Portable equipment generally uses ‘E’ sized cylinders (680 litres oxygen). Oxygen is black with a white top and nitrous oxide is blue. Safety features of dedicated nitrous oxide delivery units Current machines have several design features that ensure nitrous oxide cannot be delivered at the expense of oxygen. They include: • Nitrous oxide cut-out – if the oxygen runs out, the nitrous oxide is automatically shut off and

the patient will breathe room air • Minimum concentration of oxygen deliverable is 30 % • If the gas delivery from the common gas outlet is insufficient then air will be allowed into

the system through the ‘air entrainment valve’ • Pin index and colour coding of cylinder attachments and tubing • Air entrainment valve allows room air entry if demand outstrips supply

SCAVENGING There are two types – passive and active Passive • Open windows and doors • Fans • Place expiratory limb out of a window

Passive scavenging is no longer recommended for use with patients in a dental environment.

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Active (at 45 l/m) • Dedicated built-in systems • Off-the-shelf systems requiring minor installation procedure • Tubing systems that plug into the surgery’s wet-line slow suction system

CLINICAL TECHNIQUE Pre-sedation equipment checks This should be done before the patient enters the surgery: • Dental chair and equipment working properly • ‘In use’ and ‘spare full’ gas bottles correctly attached • Fail-safe oxygen cut out system • Reservoir bag, tubing and nasal hoods are intact and connected properly • Scavenging/venting system is working and switched on • Emergency equipment and drugs • Other equipment that may be needed – e.g. radiography equipment

Pre-sedation assessment Compliance with pre-sedation instructions and procedures is the same as for any sedation episode. • Dental and sedation history • General medical history and ASA status • Co-operation, social history and circumstances • Blood pressure (adults) • Available and appropriate escort – see earlier note • Specific written, informed consent • Pre-sedation literature • Patient is not starved • Correct nasal hood size

Procedure for inhalation sedation (first time) • Set machine mixture dial to 100% oxygen • Set flow rate dial to between 5 and 8 litres/min for adults or children (average 6l/min) • Patient is reclined in dental chair • Pass nasal hood and tubing passed over head and give to patient to place on own nose • Help patient to adjust nasal hood for comfort. Ensure good seal. Adjust the position of the

tubes behind the head for comfort and seal • Ask patient to take some deep breaths and check reservoir bag is moving properly and filling

adequately. If not, check for leaks and adjust flow rate accordingly • Check that the patient is comfortable and reassure. Discourage mouth-breathing (this will

also reduce pollution) • Mixture dial is then turned to 90% oxygen (10% nitrous oxide will be introduced)

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• Inform patient that they may start to feel symptoms of sedation: § Tingling of hands/feet/around mouth/lips (paraesthesia) § Visual and auditory changes § Feelings of lightness or heaviness § Feelings of temperature change (usually warmth) § Floating sensations/light-headedness

• Be positive, calming and reassuring • Verbally reinforce slow, calm deep breathing through the nose. Avoid the patient talking too

much as it lessens the sedative effect. Use ‘closed questions’ with simple yes or no answers • After one minute adjust the mixture dial to 80% oxygen (20% nitrous oxide will be

introduced) • Wait for one minute • Introduce further increments of 5% nitrous oxide at one-minute intervals until the desired

effect is reached • Concentrations between 20 and 50% are usual for adults • Continually monitor the patient – check:

§ Level of consciousness § Demeanour/actions/responses § Skin colour – 10% of patients vasodilate and may feel warm and sweat a little § Airway patency § Breathing rate and depth – as the patient relaxes their breathing and depth rates will

change. Match the machine’s flow rate to the patient § Mouth opening on request

Signs of sedation Nitrous oxide at this concentration may be more anxiolytic than sedative. The patient may appear quite alert and responsive but will be relaxed and accept treatment. • Acceptance of treatment – reduction of fear and anxiety • Reduced body and facial tension – general ‘detachment’ • Slowed responses – reduced frequency of blinking • Speech and voice changes • Mood change – laughing/giggling/daydreaming • Reduced pulse and breathing rates

Signs of over-sedation Maintenance of mouth opening is important. If the patient is unable to do this, they may be too deeply sedated. • Muscle rigidity and mouth closure • Disorientation and apprehension – increasing anxiety • Irritability and hallucinations • Nausea (vomiting is rare) • Emotional outbursts and crying • Unresponsiveness

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Dental treatment Introduce items of treatment slowly and progress to the next if accepted. Start with topical anaesthetic and if patient accepts local, move on to treatment. Under normal circumstances, a mouth prop is not used for inhalation sedation but may be necessary in exceptional circumstances when a mouth-open posture cannot be maintained normally. In these instances, monitoring for over-sedation should be rigorous. Recovery and discharge • To avoid diffusion hypoxia, give minimum of 2 minutes of 100% oxygen prior to removal

of nasal hood by turning the mixture dial to 100% • Praise and encourage the patient at this time complementing them on their acceptance of

treatment • Remove the nasal hood • Slowly return the patient to the upright position to guard against postural hypotension by

sitting upright too quickly • Transfer to recovery area when ready • Test for alertness and orientation prior to leaving premises • Standard written and verbal post-sedation instructions to patient and escort – no driving,

operating machinery, contact sports etc • Routine dental warnings – e.g. LA, post extraction etc

Subsequent sedation visits • For nitrous oxide ranges between 30 and 50%, the standard routine given above will be

adequate • For sedation below 20% nitrous oxide use 5% increment from the outset – young children

may sedate at quite low levels • For patients requiring high concentrations (55 - 70%) give the first four increments in 10%

stages one minute apart then continue with 5% increments to the desired level Nitrous oxide sedation as an adjunct to other techniques Nitrous oxide can be used to relax needle-phobic patients prior to venepuncture for intravenous sedation or local anaesthetics. Once this has been achieved the flow dial is returned to 100% oxygen for two minutes and the inhalation sedation can be stopped (or left on as the patient wishes). CONCLUSION Sedation with nitrous oxide is a useful technique for the mild to moderately anxious patient and avoids the need for cannulation. It requires moderately expensive equipment and effective semi-hypnotic reassurance from the dental team.

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7 Monitoring AIM OF MONITORING To maintain a continuous observation and evaluation of the patient’s physiological and psychological status, together with the response to any changes to the patient management. This may be achieved by clinical monitoring alone using principally observation, sound and feel, or in combination with the aid of electro-mechanical monitoring devices designed to measure specific functions. A very high proportion of critical events are preventable and can be attributed to lack of vigilance, or proper understanding and evaluation of the patient’s condition. A comprehensive pre-operative medical history is mandatory in preventing a critical incident by paying special attention to the patient’s appropriate vital signs. During treatment under sedation, the monitoring of the level of consciousness is achieved by talking to the patient and assessing their response. This is used as feedback to determine the correct end point during induction. The patient should always be able to respond to their normal methods of communication, which is usually verbal command. The aim in monitoring a patient, whether sedated or not, is to increase the patient’s safety during the dental procedure. It should commence from the initial contact and continue to the discharge of the patient. The six vital signs

1. Heart rate, rhythm, and character (pulse) 2. Blood pressure 3. Respiration 4. Temperature 5. Height 6. Weight

Patient’s demeanour and levels of anxiety should be included when considering monitoring for sedation. PRE-OPERATIVE MONITORING The pre-operative monitoring of the appropriate vital signs, together with anxiety levels, should form part of the initial assessment of the patient. This is because realistic resting levels of their vital signs are better achieved when the patient is less stressed at the assessment appointment. It also helps to choose the most appropriate form of sedation and dental treatment indicated for the patient. The appropriate pre-operative levels should be noted and form part of the patient’s contemporaneous records.

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RESPIRATION This is the most important of the vital signs to monitor as it is depression of respiratory function which leads to cardiac dysfunction. Early recognition and correction of respiratory inadequacy will prevent a more serious problem developing. Adequate respiratory exchange can be monitored by:

1. Observing respiratory rate – 12-16 breaths per minute. Rapid breathing indicates anxiety or pain. Reduced breathing can result from an overdose or too rapid administration of a sedative drug.

2. Observing normal chest movements. Movement is not always a guarantee of

respiratory exchange. Chest and diaphragm movement indicates that the patient is making the mechanical movements, but the airway may be blocked by the tongue or foreign material preventing respiratory exchange. A see-saw movement of the chest and abdomen, together with a tracheal tug and no breath sounds indicates total obstruction.

3. Listening to breath sounds.

• Normal breathing at rest is silent. Breath sounds result from a partial obstruction of the airway

• Snoring is an upper airway obstruction as a result of the soft palate and tongue relaxing and falling back to partially occlude the oropharynx. This is best corrected by lifting the chin which pulls the tongue forward

• Gurgling, indicating that fluid from the mouth or vomit has accumulated in the oropharynx. This can be cleared by good quality suction to prevent inhalation

• Crackling, caused by secretions accumulating in the upper bronchial tree. The patient has difficulty with removing the secretions by coughing. This may be noted in the later stages of a cold or flu. It is one of the indicators of COPD together with the use of accessory respiratory muscles in the neck and shoulders and a possible change in the colour of the patient

• Wheezing is a lower airway obstruction caused by bronchospasm. It is treated by the use of a bronchodilator such as salbutomol inhalation if the patient is conscious or IM/IV if unconscious

• Crowing / stridor. This is caused by a partial laryngospasm resulting in the passage of small quantities of air inhaled with effort past the vocal chords and can lead to complete obstruction. It is managed by suction and mechanical removal together with positive pressure oxygen ventilation

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4. Observing colour:

It is particularly important to note any change in colour of the patient. • Pale / white – anaemia or about to faint • Red – raised blood pressure or “pink puffer” in COPD • Blue – hypoxia • Grey – myocardial infarct

5. Observing movement of the reservoir bag if inhalation sedation or oxygen is administered.

CARDIOVASCULAR MONITORING Pulse Pulse is detected where an artery is adjacent to a firm structure and is palpated by the fleshy tips of 1 or 2 fingers. Beats are counted for 15 or 20 seconds, and multiplied up to give beats per minute (bpm).

Rate Normal 70 – 80 bpm Tachycardia > 100bpm Bradycardia < 50bpm Rhythm Regular or irregular Note types of irregularity Volume Normal Bounding Raised BP Feeble Low BP -? Faint

Sites of pulse

• Radial – Lateral wrist • Brachial – Medial ACF • Carotid – Groove between sternomastoid and trachea • Facial – Lower border of mandible • Temporal – Anterior tragus of ear

Blood Pressure (BP) BP is measured using a stethoscope and a sphygmomanometer. Readings are in millimetres of mercury (mmHg) derived from the old mercury manometers that were originally used to measure BP.

Sounds are only heard when there is turbulence created by the blood being forced past the obstruction of the inflated cuff. The cuff is inflated to occlude the artery and then slowly let down.

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Systole is the maximum pressure created by the contraction of the heart and is noted as the first sound is heard in the stethoscope, when the heart is just able to exceed the cuff pressure. Diastole is noted when the sound disappears or becomes muted and the flow in the artery is unimpeded and returns to laminar flow. This is the resting pressure of the heart in between contractions. Blood pressure is recorded as the systolic pressure over diastolic pressure. Normal adult blood pressure is 120mm / 80mm Hg. Hypertension (raised BP) Systolic pressure > 180mm Hg Diastolic pressure > 105mm Hg Hypotension (low BP) Systolic pressure < 90mm Hg Diastolic pressure < 40mm Hg

Laminar flow pushing past

Laminar flow No Sound

No Flow No Sound

Turbulent Flow pushing past cuff obstruction creates sound

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Patients that present with abnormal BPs should be referred to their GP for investigation prior to treatment. Automatic battery-operated devices for measuring BP are becoming more popular. These are easier to use than the mechanical method and produce more consistent results when used by inexperienced staff. The devices work by sensing the pressure waves generated whilst the pulse passes along the cuff. Pulse oximeter This is a non-invasive device which measures the oxygen saturation of arterial blood together with the characters of the pulse. It accurately reflects the patient’s cardio-pulmonary efficiency and can be set with alarms to warn the operator if the readings vary outside normal limits. It is mandatory to monitor all patients with this device when they are treated under IV or high-dose oral/intranasal sedation. Method of operation Two light emitting diodes, one in the red spectrum of 680nm and one in the infrared spectrum of 940nm, transmit light across the patient’s tissue, usually across a digit using a simple probe with a sensor. The amount of light absorbed across the tissue is measured in both the wavelengths at 50 cycles per second. Only the variable signal caused by the absorption of arterial pulse flow is noted. By this method, variable anatomical features of patients are negated, such as the width of the finger or the pigment of the skin, and only the common factor of arterial pulsatile flow is recorded. A complex algorithm within the machine calculates the red to blue ratio which results in the amounts of oxygenated (red) to reduced haemoglobin (blue) that are present in the arterial blood. The results are calculated over a period of 8 – 10 beats and averaged. This gives an accuracy of between 1 and 3%. The results are therefore always in the past and represent the patient’s state about 10 seconds previously. Display The results are displayed on the machine as the % oxygen saturation (Sats) of the patient’s haemoglobin and together with the pulse rate, are displayed as figures on the face of the machine. These are accompanied by a beeping sound in rhythm with the pulse, the tone of which goes up or down to indicate the varying saturation levels of the patient’s blood. Some machines show a graphical representation of the patient’s pulse, indicating rhythm and volume, and as such equate to monitoring the pulse by palpation. This allows the sedation team to monitor the patient both aurally and by visual reference to the display.

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Alarms The machines have alarms built into the system to indicate if there are problems with recording the signal or if the patient’s values are falling outside normal levels. These alarms can be set by the operator.

Low oxygen saturation 150bpm Low pulse rate

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8 Management of Sedation Related Complications Introduction Serious complications are rare when using a single drug properly administered as described in this handbook. The risk of problems is also reduced by careful planning, updating the medical history and by the whole dental team keeping up to date. Minor problems do occur more frequently, but most can be dealt with by a well organised dental team. SERIOUS COMPLICATIONS Respiratory depression This can be caused by over-sedation due to either too rapid administration of midazolam or an overdose. It is recognised by the pulse oximeter alarm and if saturation drops significantly, the patient turning blue. All treatment should stop and the patient instructed to take deep breaths. If they fail to respond to this, the airway should be opened (head tilt/chin lift or jaw thrust) and high flow oxygen administered. This should not be via a nasal cannula but by positive pressure ventilation using a self-inflating bag. If this does not improve the situation, flumazenil 500mcgs should be administered. It is rare to have to take steps further than reminding the patient to breathe and opening up the airway. Respiratory depression can also occur due to obstruction of the airway. This can be due to blockage by water and debris in the oropharynx or downward pressure on the mandible during extraction of lower teeth. Here the solutions are better suction and supporting the mandible during the extraction. Allergy Allergy to midazolam is very rare. If a patient reports allergy to the benzodiazepines, then further investigation by a medical allergy specialist should be carried out before assuming that general anaesthesia is indicated. Allergy to latex does not preclude the use of IV or inhalational sedation as neither the cannulae nor mask contain latex. If an allergic reaction to midazolam does occur, flumazenil must not be administered. Cardiac arrest This is fortunately very rare and is more likely to be due to underlying cardiovascular disease than sedation.

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MINOR COMPLICATIONS Hypotension All sedative drugs cause a fall in blood pressure. This does not cause any particular problems during sedation but at the end of treatment, patients should be brought slowly back to the upright position. Cannulation The most common problem is failure to find a vein. With experience this becomes less frequent. Some patients are very difficult – be wary of overweight patients or those who have had numerous cannulations in the past. It is worth taking time to find a good site and consider asking a colleague for help. Failed cannulation sites should have pressure applied to minimise bruising. Hiccups This is usually associated with too rapid injection of midazolam or over-sedation. Unfortunately, midazolam induced hiccups may last longer than usual ones, making dentistry difficult. The only management is to try the usual remedies or wait for them to pass. When treating this patient in the future, midazolam should be given very slowly. Paradoxical effects There are some people who become more difficult to manage and exhibit uncontrolled behaviour and disinhibition such as movement, and are noisy and often tearful. These tend to be younger people but there is no way of predicting who is going to react in this way. Inexperienced sedationists often think that they have under-sedated and administer more and more drug which only makes the patient more difficult to manage. The only course of action is to stop treatm,ent and reconsider, perhaps considering an alternative technique, general anaesthesia or another attempt with sedation on another day. A careful explanation must be given to the escort and to the patient. Prior warning to parents of adolescent patients that disinhibition may occur can often save embarrassment later. Prolonged recovery There is no way of predicting which patients will be affected. Most people should show signs of recovery an hour after the last increment of midazolam. If not, then reversal with flumazenil may be indicated. For future appointments it would be sensible not to book the last appointment of the day. Nausea and vomiting This is uncommon with IV sedation with midazolam, infrequent with nitrous oxide, but a common side effect of opioids. Nausea with inhalational sedation usually indicates over-sedation and the dose should be reduced. When dealing with a patient who feels nauseous, it is better to allow them to recover slowly in the dental chair. Occasionally, anti-emetics may be required.

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Under- and over-sedation This usually occurs with the less experienced sedationist who in