Inhalation sedation is a form of conscious sedation where an inhaled drug should:
Depress the central nervous system (CNS) to an extent that surgeons can operate with minimal physiological and psychological stress to the patient Modify the patient's state of mind such that communication is maintained and the patient can respond to verbal command Carry a margin of safety wide enough to render the unintended loss of consciousness and loss of protective reflexes unlikely.
Medical uses The following are possible uses for conscious sedation "dental anxiety and phobia, a need for prolonged or traumatic dental procedures, medical conditions potentially aggravated by stress (such as ischaemic heart disease, hypertension, asthma and epilepsy), medical or behavioural conditions affecting a patient's ability to cooperate, special care requirements".
Side effects Complications from inhalation sedation are rare, and are those events that require intervention to correct adverse physiological responses. They include over-sedation, respiratory depression/apnoea, unconscious patient, airway obstruction, vomiting, idiosyncratic responses, delayed recovery, and failure of conscious sedation. Few absolute contraindications exist, however, "relative contraindications are important and can only be considered following a full assessment." They include:
Medical conditions that would compromise the inhalation of the sedation medication, such as the common cold, tonsillitis, severe COPD or nasal blockage Neuromuscular diseases affecting the respiratory system, such as multiple sclerosis and myasthenia gravis Women in the first trimester of pregnancy Medical or behavioural conditions that limit a patient's ability to understand the procedure Claustrophobia or "fear of the mask".
Patient assessment and selection
On a visit prior to the treatment session, the anesthesiologist makes a full assessment to determine the need for sedation and the technique most suited to the individual patient. This consists of a detailed record of the patient's history and a thorough examination. A medical, dental, and social history covers the patient's age, state of health, social circumstances, drug history, and any special needs. This helps determine the sedation technique most appropriate for a positive outcome for each individual. The examination takes into account the patient's general appearance, skin colour, pulse, blood pressure, and respiration rates. Only patients in ASA classes I and II are normally suitable for sedation in the primary care dental setting. Patients in ASA class III or IV should be referred to an appropriate secondary care (i.e., hospital) establishment with critical care facilities.
Contraindications Inhalation sedation using nitrous oxide has a long history of safe use in both medicine and dentistry. It can therefore be used safely in most patients in the dental setting. However, in some patients sedation with nitrous oxide would be unsuitable. Some examples are below.
A patient who is unable to use a nasal mask. This is considered an absolute contraindication. Inability to use a mask can either be due to anatomic and/or disease-induced nasopharyngeal obstructions, or due to psychological and/or cognitive disturbances that lead to intolerance of mask placement. Examples of such patients include those with upper respiratory infections; severe sinusitis; and uncooperative paediatric patients or those with a fear of nasal masks. Patients who have recently undergone ear surgery. This is because any condition that compromises the patency of the eustachian tube increases the likelihood of pressure build up in the middle ear in the presence of nitrous oxide. Patients diagnosed with certain psychological disorders for example; schizophrenia or bipolar disorder. This is a relative contraindication because nitrous oxide sedation has been successfully used in patients with other personality and psychiatric disorders. The key concern with these patients is the use of nitrous oxide in addition to the many other psychotropic agents that they are already taking. This may further alter such patients’ disposition and lead to highly unpredictable results. Prior medical consultation is highly recommended for this group of patients. Pregnant patients. This is also a relative contraindication because retrospective studies have failed to identify any adverse outcomes for either the patient or the foetus. However, nitrous oxide sedation, like any other elective dental treatment, should be avoided during pregnancy. This is especially true in the early weeks of pregnancy to minimize the risk of possible toxicity to the developing embryo. Necessary/emergency dental care that requires the use of nitrous oxide to reduce stress should not be denied to a pregnant patient. Pre-cooperative patients. This is because the patient must understand they must minimize talking and mouth breathing to facilitate proper sedation. Patients with respiratory conditions such as COPD. These patients depend partly on a low blood oxygen to initiate a breathing stimulus, so inhalation sedation removes that hypoxic drive.
Problems Inhalation sedation with nitrous oxide/oxygen is a well recognised safe and effective technique. The desirable effect of the procedure is to relax the patient while maintaining verbal contact. Compared to other sedation agents, it causes minimal physiological stress to the patient and risk of loss of consciousness is less likely. However, problems can still arise. It is vital the dental staff are appropriately trained and qualified in dealing with complications and medical emergencies. Administering oxygen is of highest importance in an emergency situation. If patient is showing signs of oversedation, the concentration of nitrous oxide should be immediately reduced, and the oxygen concentration should be increased. All patients undergoing treatment under sedation should be continually assessed in the following:
Respiratory rate Heart rate Oxygen saturation Colour of skin Level of consciousness Any deviation from the normal values should prompt the dental clinician to lighten the sedation.The dental clinician can recognise and deal with the following sedation related complications:
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