Pain and anxiety management has always been an integral part of dentistry.1
Dentists generally use local anesthetic for painful procedures. Some procedures, however, require greater levels of pain and anxiety management than can be provided by local anesthetics alone.2
Intravenous drugs can cause a level of altered consciousness or sedation that provides a comfortable environment for otherwise noxious procedures.3,4
In-office sedation may negate the need to expose the patient to a general anesthetic, which requires a hospital environment in Australia that may be hard to access and expensive for the uninsured.5
The question that this study sought to answer was whether an appropriately trained operator/sedationist, supported by a team of trained dental assistants, could maintain consistently normoxemic (safe) oxygen saturation levels in the private practice dental setting.
The Faculty of Dentistry, University of Sydney, has offered a postgraduate Diploma in Clinical Dentistry (Conscious Sedation and Pain Management) since 1990. This 2-year, part-time program is a competency-based course that requires logged proof of successfully completed tasks. Candidates are given set tasks, including extensive training in the support of the unconscious human airway, the use of facemasks, Guedel airways, the use of laryngeal masks, and oral endotracheal intubation. Simulation training in the management of medical emergencies and crisis resource management is covered in great detail. Pharmacology, medical history taking, staff requirements, and training form part of the program. Two assignments and 1 dissertation need to be completed, and a minimum 14 weeks of in-hospital time is usually required over the 2-year period to satisfy the logbook requirements. Final examination includes both clinical and written examination and involves an external examiner, a specialist anesthesiologist, and a member of the faculty. Dr Viljoen has completed the Graduate Diploma in Clinical Dentistry as well as all 6 units of a training program provided by the Australian Society for the Advancement of Anaesthesia and Sedation in Dentistry (ASAASD), and received private mentoring with a specialist anesthesiologist over a 2-year period that included the supervised provision of intubated and nonintubated general anesthesia. Dr Viljoen has attended an annual Advanced Medical Simulation training program each year since graduating in 1994. This background is crucial for dentists to safely use propofol either alone or in combination with midazolam and fentanyl.
The Royal Australian College of Dental Surgeons and the Australian and New Zealand College of Anaesthetists have formulated guidelines for safe in-office dental sedation, which are outlined in policy document PS21 (RACDS/ANZCA PS21). The guidelines cover the following:
- Introduction: Conscious sedation is defined, as are potential risk factors.
- General principles: These cover medical history (ASA classification), consent, skills in airway management, avoidance of intended loss of consciousness, record of drugs administered, and use of local anesthesia to provide analgesia.
- Staffing: A third person, solely responsible for monitoring the patient, must be present. If general anesthesia is sought, an anesthesiologist must be present.
- Facilities: Room size, lighting, suction, availability of pulse oximetry, a defibrillator, emergency drugs, and positive pressure oxygen ventilating equipment are defined.
- Monitoring: Pulse oximetery must be used, and pulse rate, oxygen saturation, and blood pressure must be monitored and recorded.
- Oxygenation: Supplemental oxygen should be used because sedation can cause depression of respiratory drive.
- Drugs used for sedation: Commonly used sedation agents are mentioned as well as the fact that if anesthetic drugs are used, they must be in such low doses that unintended loss of consciousness is avoided.
- Training in sedation for dental procedures: The Graduate Diploma (University of Sydney) or equivalent is defined as the minimum standard, whether the sedation is given by a dentist or a medical practitioner.
- Specialized equipment for nitrous oxide sedation: Oxygen flow rates, scavenging, the use of a nonreturn valve, servicing of equipment, and the need for an oxygen alarm are covered.
- Discharge: Recovery room equipment and staffing requirements, responsibility for discharge, and other anesthetic reference documents are discussed.
- Appendix I: The ASA classification system is defined.
- Appendix II: The emergency drugs required, including epinephrine, atropine, lidocaine, naloxone, flumazenil, and portable oxygen, are listed.
There are few references in the dental literature that specifically measured the safety of sedation in dentistry. Many studies show a clear link between use of sedation and risk of hypoxemia.6,7
However, no dental references were found in which the oxygen saturation levels recorded during sedations were used as a determinant of safety.
Perrott and colleagues8
reported on 34,191 patients who underwent oral surgical procedures using various anesthetic techniques. In this study, 5299 patients were treated using conscious sedation. The complication rate was 1.3%, although no details of the nature of the complications were given, other than that they were “minor and self-limiting.” The authors concluded that conscious sedation was safe and associated with a high level of patient satisfaction. Milgrom and colleagues9
reported on 207 sedations that tested the hypothesis that combined drug therapy (midazolam and fentanyl, or a double-blind placebo) results in significantly poorer safety but no difference in efficacy, compared with the single drug approach. They found that the addition of the narcotic resulted in apnea in 63% of cases versus 3% in the midazolam-only group. Interestingly, patients in the combination drug group were 4 times more likely to report an “excellent sedation” versus “good, fair, or poor” in the single drug group. Jastak and Peskin10
reported on 13 deaths under dental sedation between 1974 and 1989 in the USA. They examined the physical status of the patient, anesthetic technique used, probable cause of the morbid event, avoidability of occurrence, and contributing factors. They found that most patients were classified as ASA II or III with significant pre-existing conditions (obesity, cardiac disease, obstructive pulmonary disease). Hypoxemia was the most common cause of untoward events. Most events were determined to be avoidable. The authors felt that sedation risks increased significantly in patients with a score of greater than ASA I and with extremes of age.
Midazolam, fentanyl, and propofol all depress respiratory drive and increase risk of apnea and hypoxemia. Because in-office dental sedations should be carried out on reasonably healthy, ambulatory patients (ASA I and II), one measure of safety is to examine the oxygen saturation levels recorded during sedations because it is hypoxemia that poses the greatest risk of morbidity or mortality to this otherwise healthy population.10
For the purposes of this study, safe oxygen saturation levels were defined as 94% and higher. The oxyhemoglobin desaturation curve is sigmoidal, and desaturation occurs very rapidly in the apneic or airway-obstructed patient once levels of 92% and lower are reached. Because rapid desaturation is an adverse event, in-office dental sedations should operate with a margin of safety. Modern pulse oximeters are accurate to within 2%,11
and therefore a value of 94% was chosen as our minimum safe limit, because it provides a 2% safety factor to cover the possible “margin of error” of the pulse oximeter.
Much has been published about the medical use of intravenous sedation. Medical sedations differ, however, in many ways from dental sedations. Local anesthetic is often not used to cover painful aspects of a medical procedure, such as a colonoscopy, and may result in the use of higher doses of sedatives versus dental sedations, during which local anesthesia is almost always utilized. A wider range of ASA class and age are sedated, and treatment may be carried out in a hospital environment under the care of an anesthesiologist with full hospital backup. Therefore, the data obtained from medical sedations should not necessarily be extrapolated to the dental setting. Dentists need to generate their own in-office evidence base.
This study sought answers to 2 questions: (a) Were safe saturation levels consistently maintained (as defined above)? (b) Did the additional use of the general anesthetic induction agent propofol in subanesthetic doses increase the risk of exposure to 2 or more low-saturation events?
Answers to these questions will add to the evidence base about the safety of the single operator/seditionist plus a team of assistants; the risk that the use of propofol may or may not pose; and the effect of age, gender, weight, ASA class, and midazolam dose on the incidence of oxygen desaturation. These results should assist both dentists and anesthesiologists to form an evidence-based opinion on the safety of in-office dental sedation in Australia.