Introduction

Careful pre‐sedation appraisal will optimise the safety and effectiveness of sedation. Patient selection and assessment is an essential prerequisite to the success of subsequent treatment under conscious sedation. The assessment provides an opportunity to obtain relevant information from the patient to determine suitability for both sedation and dental treatment. It allows the patient to discuss their treatment with the clinician and for both to establish a mutual rapport. This is of particular importance for severely anxious patients who may have lost confidence with the dental environment through previous negative experiences. Such patients need to be managed with care and reassurance to regain their trust and co‐operation.

This chapter will consider all aspects of the assessment process and discuss the relevance of certain medical conditions in the delivery of conscious sedation.

Assessment Process

Setting

A specific appointment should be arranged, whenever possible, for the pre‐operative assessment separate to the treatment day. Ideally this visit should take place in a non‐clinical, and therefore non‐threatening, environment. It is important to create a calm and relaxed atmosphere to help reassure patients and put them at ease.

History Taking

The accepted sequence of history taking, followed by examination is no different from the assessment of any patient, but there should be special emphasis on the need for sedation, reasons for treatment under sedation and the patient’s fitness to receive sedation. Only when all of this information is available can an individual treatment plan be formulated. It is also important to gain indirect information about patients from the way they respond to questioning and, even more importantly, from the initial examination.

The history must include details of the nature of the patient’s dental anxiety, particular difficulty with dental treatment, for example a gag reflex, the past dental history and current dental symptoms, a thorough medical history and information on social circumstances. The medical history is the most important part of the history and will be covered in some detail.

Nature of Dental Anxiety

It is important from the outset to determine the nature of the patient’s anxiety. Some people are anxious of ‘dentistry’ as a whole, while others have a specific anxiety about ‘things in the mouth’ or ‘the dental drill’ or ‘dental injections’ or ‘having a tooth pulled’. The underlying basis for many of these anxiety‐provoking stimuli is frequently the fear of ‘pain’. Unfortunately, dentistry has always had a close association with pain and the possibility of pain‐free dental treatment can be a very difficult concept for anxious patients to accept.

The extent of dental anxiety can range from mild apprehension to true phobia. Many phobic patients never actually make it to the surgery. Those who do, may present with poor dentition for routine conservation and are very different from the patient who has excellent dentition but is anxious about undergoing third molar surgery. It is important to try to gauge the degree of anxiety, and it can be useful to ask the patient about his or her fears and concerns about the dental visit.

This can help to break the ice and will steer the discussion in the right direction without unduly provoking sensitive emotions. In the case of fear of ‘injections’ or ‘needles’, the patient must be asked if this is a general fear or just specific to dentistry. Many patients have a fear of oral injections but will accept an injection in the arm. A true needle phobia will contraindicate the use of intravenous sedation without some form of premedication, topical anaesthetic agent or cognitive desensitisation therapy.

Dental History

A detailed knowledge of the past dental history is essential for planning dental treatment and determining suitability to receive treatment under sedation.

The dental history should ascertain details of why the patient is being considered for treatment under sedation. If the patient is dentally anxious then a history of when he or she first became anxious should be noted. For many patients this will have started with a bad experience in childhood but for others the onset of their anxiety may have been more recent, for example, following a traumatic extraction. Patients frequently state that they were quite happy to receive routine treatment until a specific dentist hurt them during treatment, which subsequently made them anxious about re‐attending.

Information should also be sought about when (or even if) the patient last underwent routine dental treatment and the type of dentistry received. It is helpful to find out whether the patient has received sedation previously, what type of sedation this was and how they felt about it.

Finally, patients should be questioned regarding their concerns about their teeth, how they feel about their health and the appearance of their dentition, their future aspirations and any current dental symptoms. All of this information should then be compiled and used for treatment planning.

Medical History

The aim of medical history taking is to determine the fitness of the patient to undergo sedation and is the most important factor to consider during assessment. A full medical history should be taken in the same way as for any patient presenting for dental treatment but special note should be made of cardiovascular, respiratory, hepatic and renal disease. Full details of current drug therapy will alert the dentist to potential drug interactions and may reveal undisclosed conditions. Patients at the extremes of the age range, pregnant women and patients with disabilities and impairments deserve special consideration in relation to sedation. A medical history questionnaire may be helpful to ensure that all areas are covered and can provide prompts for further questioning.

Assessment of Fitness for Sedation

A useful means of estimating fitness for sedation is to use the classification system introduced by the American Society of Anesthesiologists (ASA). In this system patients are allocated to specific grades according to their medical status and operative (or sedation) risk. The classification uses six grades (Table 3.1).

ASA I

Patients assessed as ASA class I are ideally suited to receive conscious sedation. They pose the lowest risk and can be safely treated in general dental practice. However, the possibility of undiagnosed medical problems should always be borne in mind, even in apparently healthy patients.

ASA II

ASA class II patients have a mild systemic disease. Examples might include well‐controlled asthma, diet‐controlled diabetes or mild hypertension. In addition to the true ASA II patients, it is also wise to include those who are extremely anxious about dental treatment. Extremely nervous patients have high circulating levels of endogenous adrenaline and are more prone to complications during sedation. Patients of ASA II present a higher risk but, with appropriate precautions, many are also suitable for treatment under sedation in dental practice.

ASA III

Individuals in ASA class III represent a group presenting a difficult choice as far as sedation is concerned. This group includes patients with, for example, stable angina, well‐controlled epilepsy, chronic bronchitis, congestive heart failure or well‐controlled insulin‐dependent diabetes. These patients have a severe but controlled systemic disease, which may limit normal activity but which is not incapacitating. The use of sedation to reduce physiological and psychological stress can be very beneficial to this category of patients and may well reduce the risk of an acute exacerbation of the medical condition during dental treatment. However, such patients do present an increased risk and most of them should be referred to a specialist environment where extra support is available.

In addition to the true ASA III patients, it is also wise to include in this group patients who have no systemic disease, but who have a high body mass index or are over 70 years of age. Patients who are significantly overweight may have a reduced respiratory capacity and older people are generally more sensitive to sedation agents and their physiological processes are slower.

ASA IV

ASA class IV represents patients who have severe life‐threatening systemic disease. Examples include patients who have had a recent myocardial infarction, uncontrolled diabetes, uncontrolled epilepsy or severe emphysema requiring oxygen therapy. People in this category should usually be treated in an anaesthetist‐led hospital day‐stay facility where full medical and anaesthetic support is available.

ASA V

For patients in ASA class V, who are moribund, only emergency treatment would ever be provided. Such patients may be sedated for medical reasons but rarely for the purpose of providing dental treatment.

It is important to note that the ASA classification is not infallible, and there is some overlap between categories. However, it does represent a relatively simple means of determining the risk of sedation. It is, therefore, essential to assess patients on an individual basis taking into consideration all elements of their medical and social history.

It can be difficult to classify patients with multiple conditions, for example a mildly asthmatic patient who has well‐controlled diabetes. Where any condition falls into the higher ASA group this should be recorded as their physical status and the patient treated accordingly. In this way, the risk to the patient is reduced and the dental treatment can be provided safely and effectively.

Relevance of Specific Medical Conditions

To accurately assess and categorise the medical fitness of a patient for sedation, the dental clinician must have a clear understanding of specific pathological and physiological processes and their relevance to sedation practice.

Cardiovascular Disease

Disease of the heart and circulatory system will affect a patient’s fitness for treatment under sedation. In the Western world a high proportion of the population suffer from ischaemic heart disease and have a history of angina or a myocardial infarct. Other conditions such as valvular or congenital heart disease may also present to the dental clinician. In these patients the stress associated with dental treatment can lead to high levels of circulating adrenaline. This in turn causes tachycardia and hypertension, thereby increasing the load on the heart. When the cardiac status is already compromised stress may induce an acute exacerbation of the medical condition. The classic example of this would be the patient with stress‐induced angina, who is at increased risk from acute myocardial infarction.

Hypertension resulting from vascular or renal disease affects many people, especially with increasing age. The stress of treatment and the effects of the sedation agent can cause significant fluctuations in blood pressure.

Patients with a blood pressure below 160/95 mmHg should be able to receive sedation safely in dental practice. If the resting blood pressure is above this level, referral for medical evaluation before sedation is essential. In this regard, the diastolic reading is probably the more significant of the two values. As mentioned earlier, however, it is sudden changes in blood pressure that give rise to greater concern than the initial readings.

Although patients with cardiovascular disease benefit considerably from receiving treatment under sedation, they do present a special risk. Their limited ability to cope with stress increases the chance of an acute exacerbation of the disease during the sedation appointment. Many are also taking cardio‐active medications which can interact with sedation agents.

Respiratory Disease

Virtually all sedation agents cause some degree of respiratory depression, therefore good respiratory function is essential for patients undergoing sedation. Healthy patients with a normal respiratory capacity are able to compensate for the mild depressive effects of sedation drugs. However, patients with respiratory disease have less respiratory reserve and can easily become deoxygenated under sedation.