The need for sedation in dentistry is evident. According to Chanpong et al., in 2003 of Canadians, about 10% of the general population were somewhat afraid of dentistry, 5% had a high fear level, and many appointments were avoided or canceled in relation to these patients’ worries and fears of undergoing dental treatment. Furthermore, this study demonstrated that these same fearful patients were requesting sedation services. Patients receiving the gamut of treatment procedures not just extensive surgical procedures are requesting sedation services.
A number of organizations have listened to these requests and have answered them by providing sedation courses for dentists. There are an ever-growing number of sedation courses being offered throughout Canada and the United States. One of the more frequent ways for dentists to begin providing sedation procedures to their patients is through oral sedation.
Dentists are commonly taught to achieve mild or moderate sedation via oral sedation with the use of benzodiazepines. Benzodiazepines are used to reduce anxiety, and to provide sedative effects, amnesia, muscle relaxation, and anti-convulsive effects. The effects are dose-dependent and have a long history of being used safely in the dental setting. Common benzodiazepines being used for these purposes are triazolam, lorazepam and diazepam.
Another common technique taught with oral sedation using benzodiazepines is a pharmacological rescue technique using submucosal/sublingual (SM/SL) injections of flumazenil.
Flumazenil reverses the effects of benzodiazepines. It does so by competitively antagonizing the benzodiazepine at the receptor site level. Flumazenil is only approved for intravenous (IV) administration. The prescribed IV administration technique is to titrate slowly to arousal with 0.2 mg increments. It is supplied in a 0.1 mg/ml concentration only. Cautions to keep in mind with flumazenil use include eliciting a seizure in patients who control their seizures with benzodiazepines, and watching for patient resedation later due to the relatively short duration of action with flumazenil in relation to most benzodiazepines.
This agent should only be used in an overdose emergency situation that has become difficult or impossible to manage non-pharmacologically. For instance, the sedated, unconscious patient with apnea, upper airway obstruction, or hypoventilation any of which could lead to debilitating injuries such as brain damage due to the lack of oxygen delivery.
The problem with 0.2 mg SM/SL flumazenil administration is as follows. Giving the drug by this route requires more time to reach effective plasma levels as opposed to the intravenous route of administration. Even when used by the intravenous route the time of onset is 1 to 3 minutes. During this time, the dentist trained to use oral sedation should be familiar enough with noninvasive airway maneuvers that keep the airway patent if necessary. Also, a dose of 0.2 mg SM/SL is probably not a large enough dose have the desired effect. Furthermore, providing larger doses via the intraoral SM/SL method can be unsafe, as there is a large venous plexus below the tongue which can further create a bleeding problem or compromise the airway, you could even injure the lingual nerve.
For these reasons it is not recommended to use the SM/SL technique as a rescue method in the case of a benzodiazepine overdose. The more appropriate management technique would be to use this medication through intravenous administration and then only as a last resort. Basic life support skills such as supporting the patient’s airway by a head-tilt chin-lift and providing the patient with oxygen are more important. In absolute desperation when intravascular access cannot be achieved, intramuscular injections totalling the likely rescue dosage of 0.6 mg to 1 mg (which requires 6 to 10 ml of volume) can be utilized in an attempt to reverse the patient’s overdose.
Sedation dentistry via the oral route is a marvelous option for dentists and patients alike, but as practitioners, we have a responsibility to be able to get out of any foreseeable problem that we might get ourselves into. The submucosal or sublingual injection of flumazenil is not likely to do that.OH
Dr. Campbell is a first-year resident in the postgraduate Dental Anaesthesia program at the University of Toronto.
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