Overview

An Overview of Outpatient Sedation and General Anesthesia for Dental Care in California

Tim Silegy, DDS, and Roger S. Kingston, DDS

Copyright 2003 Journal of the California Dental Association.

Author

Tim Silegy, DDS, is a diplomate of the American Board of Oral and Maxillofacial Surgery. He maintains a private practice in Long Beach, Calif.

Disclosure

Dr. Silegy gives basic, advanced, and pediatric life support lectures for CME Associates in Orange, Calif., and is the director of the oral and maxillofacial surgery assistant’s course sponsored by the California Association of Oral and Maxillofacial Surgeons in Roseville, Calif.

This paper reviews the principal pharmacologic interventions for the management of pain and anxiety in the apprehensive dental patient, including oral sedation, intravenous sedation, and general anesthesia.

Access to dental care is a highly debated issue at present, as dentists, public health officials, politicians, and patient advocates examine the demographics and distribution of dental care in California.

One of the barriers to dental care for a significant population subgroup, possibly as large as 30 percent, is fear and anxiety.1 At best, dental patients who experience fear, anxiety, and hypersensitivity to pain will move in the dental chair and recall dental visits negatively. Most significantly, many patients will avoid needed dental care, consequently suffering unnecessary morbidity.

Perhaps dentistry’s greatest contribution to humankind has been the introduction of anesthesia and anesthetic agents to dull or eliminate the physical and psychological effects of pain. Beginning in the 1840s with the popularization of ether by Dr. William T.G. Morton and nitrous oxide by Dr. Horace Wells, the interest of dentists in improving the dental experience is well-documented and voluminous.

In the 1960s, Southern California pioneers such as Drs. Nils Jorgensen, Oran K. Bullard, Adrian Hubbell, Howard Davis, Ed Boller, Lee Reeve, John Lytle, and Frank McCarthy introduced and refined intravenous sedation and general anesthetic techniques for in-office dentistry. These pioneers had concern for patient safety and advocated for safety standards and governing legislation.

Currently, the dental anesthesia faculties of the California dental schools teach undergraduate dental students, graduate students, and postgraduate practicing dentists to provide dental care with sedation and general anesthesia. The University of California at Los Angeles and Loma Linda University offer two-year residency training programs in dental anesthesiology.

Dental anesthesiology, while not recognized as a specialty by the American Dental Association, is a field wherein trained and qualified dentists limit their practice to teaching and providing anesthesia services for dentistry. Professional organizations such as the American Society of Dentist Anesthesiologists and the American Dental Society of Anesthesia exist to promote excellence in dental anesthesia through education and research.2

Equipped with portable monitors, many dentist anesthesiologists provide a full range of anesthesia services, ranging from light sedation to general anesthesia, for children, adults, and individuals with special needs, in the offices of primary care dentists. This represents a considerable cost savings compared to treating these same patients in outpatient surgical centers and hospitals.

California Law

The Dental Board of California has implemented legislative regulations to establish minimum standards for training, facilities, and monitoring for most anesthetic techniques. Guidelines developed by the Southern California Society of Oral and Maxillofacial Surgeons served as a framework for this legislation.

Guedel was the first to describe anesthetic levels.3 His observation of patients undergoing ether anesthesia provides a basis for our understanding today. The American Society of Anesthesiologists, the American Dental Association, the American Academy of Pediatric Dentists, and others have defined anesthetic depth.4-6 Because airway protective reflexes are progressively depressed with increasing depth of anesthesia, more training and experience is needed to manage the potential complications associated with deeper levels of anesthesia. Therefore, the California Dental Practice Act defines three anesthetic levels and regulates their administration .7

Pediatric Oral Conscious Sedation

Pediatric oral conscious sedation is a minimally depressed level of consciousness in a minor patient, produced by oral medication, that retains the patient’s ability to maintain independently and continuously an airway, and respond appropriately to physical stimulation and verbal command. “Minor patient” means a dental patient younger than 13.

Conscious Sedation

Conscious sedation is a minimally depressed level of consciousness produced by a pharmacologic or nonpharmacologic method, or a combination thereof, that retains the patient’s ability to maintain independently and continuously an airway and respond appropriately to physical stimulation and verbal commands. Conscious sedation does not include conditions resulting from the administration of oral medications or the administration of a mixture of nitrous oxide and oxygen, whether administered alone or in combination with each other. The drugs and techniques used in conscious sedation shall have a margin of safety wide enough to render unintended loss of consciousness unlikely.

General Anesthesia

General anesthesia is a controlled state of depressed consciousness or unconsciousness, accompanied by partial or complete loss of protective reflexes, produced by a pharmacologic or nonpharmacologic method, or a combination thereof.

In California, all licensed dentists may administer local anesthesia and nitrous oxide-oxygen to adults and children. The same dental license also allows oral sedatives to be administered to patients 13 years of age and older. Dentists wishing to administer oral sedatives to children, intravenous sedation, or general anesthesia, require a special permit to do so. The requirements for these permits are listed in Table 1.

Indications

Conscious sedation and general anesthesia in the dental office are generally limited to healthy (ASA Class I and Class II) patients. When interviewing the patient at the time of consultation, in addition to reviewing a patient’s medical history and performing a dental exam, it is important for the dentist to evaluate the patient’s level of anxiety. Patients with a history of “bad” dental experiences in childhood, claustrophobia, low pain tolerance, or substance abuse are likely to benefit from some type of pharmacosedation.

Sedation is defined as a state of drowsiness or mental clouding. Frequently used synonyms include anxiolysis or relaxation. The limbic system is responsible for awareness, and inhibition of this area of the brain results in a sense of tranquility and well-being. Hypnosis refers to central nervous system depression, principally of the reticular activating system, resembling normal sleep. Agents that produce these effects are collectively referred to as sedative-hypnotics. As in normal sleep, appropriately sedated patients may close their eyes and have dreams but can independently maintain their airway and be easily awakened.

Commonly Used Agents

The principal inhalational anesthetic agent in use today for sedation is nitrous oxide.8 The use of nitrous oxide is extensively reviewed elsewhere in this issue by Dr. Stanley Malamed. While some have advocated the use of halogenated hydrocarbons (desflurane and sevoflurane) to provide sedation, the need for anesthesia machines and vaporizers limits their use principally to outpatient surgical facilities and hospital operating rooms.9-10

A number of non-inhalational drugs have sedative and, in higher doses, general anesthetic properties. Benzodiazepines, barbiturates, opioids, dissociatives, and others are commonly used alone or in combination. These agents are summarized in Table 2.

Benzodiazepines

Benzodiazepines act on gamma-amino-butyric-acid receptor complexes in the central nervous system. When activated, these receptors increase the passage of chloride ion through discrete channels, hyperpolarizing nerves in the limbic system, which results in a sense of relaxation. Benzodiazepines have little analgesic effect and are frequently used in conjunction with opioids when used for intravenous sedation.

Diazepam was first synthesized in the early 1960s and commonly referred to as “mother’s little helper.” At one time, it was the most frequently prescribed medication in the United States.11 As is the case for all benzodiazepines, diazepam effectively reduces anxiety and is a profound amnestic. Diazepam is available as a pill or dissolved in propylene glycol for injection. Propylene glycol can irritate smaller veins and has been associated with phlebitis. Diazepam has a wide margin of safety and is effective both orally and intravenously. In the case of intravenous sedation, its long duration of action makes it a good choice for longer procedures. Diazepam is metabolized in the liver. An active byproduct of this metabolism is oxazepam, which contributes to a reduced yet prolonged sedative effect. Care must be taken when using the drug on elderly patients, as they are typically much more sensitive to the sedative effect and tend to need a longer period of recovery.

Midazolam is about 2.5 times as potent as diazepam and has greater amnestic properties. It is water-soluble and is distributed as an aqueous solution for injection. It is also available premixed with cherry syrup for oral administration. Midazolam undergoes rapid redistribution and has a significantly shorter half-life than diazepam, making it an ideal agent for short procedures. Additionally, because it has no active metabolites, there is little “hangover” effect as is the case with diazepam.

Triazolam is a benzodiazepine designed principally to treat insomnia. It is distributed in pill form and has been found to be very effective when used for sedating anxious dental patients. Following oral administration, it has a peak effect at one hour and a half-life of two to three hours. Kaufman and colleagues found a 0.25 to 0.50 mg oral dose of triazolam taken one hour prior to treatment to be as efficacious as a mean dose of 19.3 mg of diazepam titrated intravenously.12 Baughman and colleagues found 0.5 mg of oral triazolam to produce significant amnesia.13

The administration of multiple doses of triazolam with early discharge after reversal with sublingual flumazenil has been advocated by several continuing education seminars.14 To date, no controlled clinical studies have demonstrated this to be a safe technique.

Opioids

Opioids exert their effect on the central nervous system by interacting with specific receptors in the brain and spinal cord blunting the response to excitatory neurotransmitters, namely acetylcholine and substance P (Table 3). Because the opioid agonists are not specific for any one receptor, the desirable effects of euphoria, sedation, and analgesia are frequently accompanied by nausea, dysphoria, and respiratory depression, especially in higher doses. Consequently, they are seldom used as a lone agent for sedation.

Opioid agonist-antagonists like pentazocine, nalbuphine, and butorphanol agonize some receptors but antagonize others. They were once popular because of self-limiting respiratory-depressant effects but are seldom employed by anesthesia providers today.

Meperidine hydrochloride and fentanyl citrate are the most commonly used opioids for intravenous sedation and general anesthesia. When used in conjunction with benzodiazepines, they produce a synergistic sedative result, effectively decreasing the overall dosage of drugs needed to elicit the desired effect.

About one-tenth as potent as morphine sulfate, meperidine is a relatively weak analgesic. When used intravenously it has a duration of 30 to 60 minutes. Unwanted side effects include histamine release, nausea, vomiting, and postural hypotension. As is also the case with fentanyl, meperidine should not be used in patients taking monamine oxidase inhibitors, as delirium and cardiovascular collapse have been reported.15

Fentanyl citrate is perhaps the most commonly used opioid in anesthesia. It is 100 times more potent then morphine and has a duration of action much shorter than that of meperidine. Corresponding with increased potency is an increased incidence of respiratory depression. Too rapid an administration of the drug can also result in a spasm of the diaphragm and skeletal muscles commonly referred to as “stiff-chest syndrome.” 16 This occurs rarely in sedative doses and can be easily managed by administering a muscle relaxant.

Barbiturates

Barbiturates, like benzodiazepines, act on the gamma-amino-butyric-acid receptor complex. They are available in pill form or as a powder reconstituted for injection. Prior to the synthesis of diazepam, they were used frequently as minor tranquilizers. Today, barbiturates are used mainly to induce general anesthesia. Sodium pentothal is commonly used in the hospital environment and was the first barbiturate to be used by oral and maxillofacial surgeons for third-molar removal.17 Its tendency to cause respiratory depression and long duration of action have limited its use in the dental office, and it was superseded by methohexital in the early 1960s.

Until last year, sodium methohexital was the most commonly used general anesthetic agent in the oral and maxillofacial surgery office. Its rapid onset and relatively short duration of action make it ideal for inducing general anesthesia for short procedures like third-molar removal. Respiratory depression, laryngospasm, hiccups, and resistance are common side effects that are easily managed by experienced practitioners. Due to a manufacturing shortage in 2002, many surgeons have switched to alternative agents such as ketamine and propofol.

Ketamine

Ketamine is a phencyclidine derivative that produces profound analgesia and amnesia. Unlike other anesthetic agents, it does not depress the reticular activating system; rather, it blocks transmission of sensory impulses from the reticular activating system to the cerebral cortex at the thalamus. Consequently, there is little respiratory depression; and protective airway reflexes remain intact. It is available in liquid form for intravenous and intramuscular injection and has been administered orally. Many practitioners are concerned with reports of hallucinations while emerging from the effects of the drug. This can be prevented with the simultaneous administration of a benzodiazepine.18 Ketamine has both sympathomimetic (increases heart rate and causes bronchodilation) and cholinergic (causes hypersalivation and bronchial secretion) effects. Consequently, an anticholinergic such as atropine or glycopyrolate is frequently administered concomitantly.

Propofol

Propofol is a di-isopropyl-phenol unlike any other anesthetic agent. It is highly lipid-soluble, which accounts for its rapid uptake and short duration of action. It is a potent amnestic and has been found to be a powerful antiemetic.19 In low doses, it is an effective sedative. Due to its rapid redistribution, it is frequently administered as a continuous infusion using an infusion pump.

Anesthetic Technique

Oral Sedation

Oral (enteral) sedation is ideal for slightly anxious patients requiring traditionally nonpainful dental procedures such as cosmetic and restorative dentistry. The principal advantages of oral sedation include ease of administration, as there is no need for intravenous access, and favorable patient acceptance. Oral benzodiazepines such as diazepam and triazolam are particularly effective. When used in recommended dosages, they are very safe and carry with them very few direct contraindications. Midazolam is also an effective oral sedative; however, its use is chiefly reserved for premedication in children.

A major disadvantage of oral sedation is the inability to tailor dosages for individual patients. When taken orally, anesthetic agents are absorbed by the portal circulation and pass through the liver, where they are metabolized prior to entering the central circulation. This first pass effect makes it difficult to predict the bioavailability of the agent and, consequently, just the right dose. Drugs that are unstable in an acidic environment make be deactivated by gastric acid in the stomach.

As is the case for patients who receive parenterally administered anesthetic medications, dental patients who have taken oral sedatives should be driven to and from their dental appointments by a responsible adult and should not drive or operate dangerous machinery until fully recovered from the effects of the medication.

Intramuscular Injection

The intramuscular route of drug administration parallels oral administration. Agents undergo first-pass metabolism in the liver, making the end effect difficult to predict. The major advantage of intramuscular injection is that it requires little cooperation from the patient. Ketamine is an ideal intramuscular drug. With an onset of 10 minutes and minimal associated respiratory depression, it renders patients cataleptic, facilitating treatment or the establishment of intravenous access.

Intravenous Sedation

Contrary to popular opinion, the utilization of intravenous sedation does not directly provide for a deeper level of sedation than oral administration. The major advantage of IV sedation is that it allows the clinician to maintain precise control over the patient’s level of sedation through the administration of small incremental dosages of medication, a technique known as titration. By titrating medications, a patient’s level of consciousness can be carefully adjusted and the level of sedation controlled.

The procedure involves gaining intravenous access in the hand or forearm and maintaining it throughout the course of the procedure. Those individuals with “needle phobia” benefit from the use of topical anesthetics such as lidocaine prilocaine cream or spray refrigerants such as ethyl chloride. Patients are typically given supplemental oxygen via a nasal canula or nasal hood in conjunction with nitrous oxide. Their blood pressure and heart rate are monitored periodically and oxygen saturation is continuously monitored with pulse oximetry. A precordial stethoscope is commonly used to evaluate heart rate and breath sounds during the procedure.

Benzodiazepines are frequently used as initial agents. Small doses are administered until the patient’s eyelids droop (Verril’s sign) and his or her speech is slurred. An opioid may be added next to deepen the level of sedation and provide analgesia. While effective in reducing anxiety and blunting the pain response, IV sedation alone does not eliminate the need for local anesthesia. Consequently, care must be taken to ensure that the patient is numb prior to starting and throughout the course of treatment.

An added benefit of using a benzodiazepine-opioid combination for IV sedation is that in case of a medical emergency, both benzodiazepines and opioids are readily reversible. Flumazanil competitively displaces benzodiazepines from the gamma-amino-butyric-acid receptor complex. Naloxone is the reversal agent for opioid analgesics. Care must be taken to observe the patient after the administration of a reversal agent, as patients may become re-sedated if the half-life of the anesthetic agent exceeds that of the reversal agent. While propofol and ketamine have been used in low doses to provide sedation, it is the opinion of the authors that they do not have a margin of safety wide enough to render unintended loss of consciousness unlikely, and hence do not fall within the legislative guidelines of “sedative” agents.

General Anesthesia

General anesthesia is indicated for management of highly anxious and fearful (phobic) patients requiring restorative dentistry and for oral surgery patients undergoing procedures where local anesthesia alone would not provide sufficient comfort. This form of anesthesia is the most uniformly dependable anesthesia modality.

In the outpatient environment, a general anesthetic begins in much the same way as IV sedation. Because a deeper plane of anesthesia is expected, sedative medications may be administered more rapidly; and commonly a third agent is added to induce unconsciousness. This “balanced” anesthesia technique, provides anxiolysis, analgesia, and amnesia in a predictable and safe manner.

Dr. Adrian Hubble popularized the use of sodium methohexital for induction of general anesthesia in patients undergoing third-molar removal.20 The surge technique involves injecting an initial large bolus of the agent followed by frequent smaller boluses or “bumps.”21 This technique is still practiced by many oral surgeons today when using sodium methohexital or propofol for third-molar anesthesia.

The use of a continuous small infusion of agent is another frequently used technique, being particularly useful for longer surgical and restorative cases. Following an initial large bolus, a slow intravenous drip, or an infusion pump, administers a continuous predetermined amount of an agent or agents, allowing the practitioner to maintain tight control on the level of anesthesia. Propofol and propofol/opioid and propofol/ketamine combinations have been effectively used to provide deep sedation and general anesthesia in the ambulatory setting.22-24

For short cases such as third-molar removal, endotracheal intubation is rarely necessary when office-based general anesthesia is employed. However, because the patient’s protective airway reflex is obtunded, care must be taken to protect the airway. Placement of a 4-x-4-inch gauze as a pharyngeal shield (throat pack) is useful.

In cases where the dental procedure is expected to last longer than an hour, or when considerable water spray is going to be used, the airway can be protected with a laryngeal mask or by endotracheal intubation.

Regardless of the airway management technique employed, a dedicated person (other than the operator) must be present during a general anesthetic to manage the airway and monitor the patient.

Safety Concerns

Ambulatory outpatient sedation and general anesthesia in dentistry has an enviable safety record. Lytle and Stamper reported a mortality rate of seven deaths in 4.7 million office anesthetics administered from 1968 to 1987 by Southern California oral and maxillofacial surgeons.25 A similar survey of Massachusetts oral and maxillofacial surgeons found no deaths in 1.5 million office anesthetics during a five-year period.26

This exemplary safety record can be attributed to several factors.27 First, as previously mentioned, the sedation and general anesthesia modalities used in the dental community are generally reserved for healthy patients.

Second, most practitioners surround themselves with a highly trained team, thoroughly prepared and equipped to manage anesthetic emergencies. All personnel involved in patient care are required by law to have current training in basic life support. Practitioners holding general anesthesia permits are required to be current in advanced cardiac life support. Advanced training programs in anesthesia assisting for dental assistants are available from the American Association of Oral and Maxillofacial Surgeons and the California Association of Oral and Maxillofacial Surgeons.

Third, state law mandates that all conscious sedation and general anesthesia permit holders undergo a rigorous office anesthesia evaluation every six years. The office anesthesia evaluation was developed by the Southern California Society of Oral and Maxillofacial Surgeons in the late 1960s and was subsequently incorporated into the state Dental Practice Act. There are six components of the evaluation. The first four involve the inspection of the office physical plant, emergency equipment and monitors, emergency drugs, and records. The anesthetic team is then evaluated as common anesthetic emergencies are simulated. Finally, an actual sedation or general anesthetic is observed.

Other Options

Not all patients are good candidates for in-office sedation and general anesthesia. Patients with serious health conditions, young children with significant restorative needs, and individuals who are physically challenged, may be poor candidates for office-based treatment. Some hospitals have dental equipment that can be moved into an operating room and encourage dentists to join their medical staffs. Patients who could not otherwise have dental care -- such as those with severe physical, mental, or psychological disabilities -- can receive comprehensive dental care while anesthetized by the hospital’s anesthesia service.

Conclusion

Although access to dental care is still an issue in California, no patient should find it impossible to receive needed dental care because of fear and anxiety. Many levels of anesthetic intervention can be provided by appropriately trained dentists. Available techniques include local anesthesia, nitrous oxide/oxygen analgesia, oral sedation, intravenous conscious sedation, and general anesthesia administered in the office, a surgical center, or a hospital. The challenge for every dentist is to formulate an anesthetic treatment plan to suit each patient’s need. When dentists are consistently able to do this, patients will no longer have to fear dental treatment and our success as doctors and humanitarians will be elevated to a new, higher level.

References

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2. Mission statement of the American Dental Society of Anesthesia, Chicago.

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4. American Society of Anesthesiologists, Definition of General Anesthesia and Levels of Sedation/Analgesia. ASA Standards and Guidelines, Park Ridge, Ill, Oct 2001.

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6. American Academy of Pediatric Dentistry, Reference Manual 1998-1999. American Academy of Pediatric Dentistry, Chicago, 1998.

7. California Business and Professions Code Sec. 1646-1647.9

8. Clark MS, Brunick A, Handbook of Nitrous Oxide and Oxygen Sedation, CV Mosby, St Louis, 1999.

9. Haraguchi N, Furusawa H, et al, Inhalation sedation with sevoflurane: A comparative study with nitrous oxide. J Oral Maxillofac Surg 53(1):24-6, 1995.

10. Bandrowsky T, Orr FE, et al, Desflurane for outpatient general anesthesia in third molar extraction cases. J Oral Maxillofac Surg Feb 55(2):129-32.

11. Koerner B, The father of mother’s little helpers. US News World Report December, 1999.

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13. Baughman VL, Becker GL, et al, Effectiveness of triazolam, diazepam and placebo as preanesthetic medications. Anesthesiology 71(2):196-200, 1989.

14. Yagiela J, Personal communication, 2002.

15. Brown B, Linter S, Monamine oxidase inhibitors and narcotic analgesics: A critical review of the implications for treatment. Br J Psychiatry 151:210-2 1987.

16. Jaffe TB, Ramsey FM, Attenuation of Fentanyl-Induced Truncal Rigidity, Anesthesiology 56:562, 1983.

17. Dembo JB, The use of intravenous anesthesia and sedation technologies in oral and maxillofacial surgery. J Oral Maxillofac Surg 51(4):346-51, 1993.

18. Haas DA, Hauper DG, Ketamine: A review of its pharmacological properties and use in ambulatory anesthesia. Anesthesia Progress 39:61-8.

19. Borgeat A, Wilder-Smith OH, et al., Subhypnotic doses of propofol possess direct antiemetic properties. Anesth Analg 74:539-41, 1992.

20. Hubble AO, Methohexital sodium anesthesia for oral surgery. J Oral Surg 18:295, 1960.

21. Drummond-Jackson SL, A milestone in intravenous anesthesia. Brit Dent J 113:404, 1962.

22. Candeleria LM, Smith RK, Propofol infusion technique for outpatient general anesthesia. J Oral Maxillofac Surg 53(2):124-8, 1995.

23. Badrinath S, Avramov MN, et al, The use of a Ketamine-propofol combination during monitored anesthesia care. Anesthesia Analgesia 90: 858-62, 2000.

24. Toth E, A comparison of remifentanyl/midazolam with remifentanyl/propofol for monitored anesthesia care during extracorporal shockwave lithotripsy. Masters Thesis, University of Kansas, Department of Allied Health, Division of Nurse Anesthesia, 1998.

25. Lytle JJ, Stamper EP, The 1988 anesthesia survey of the Southern California Society of Oral and Maxillofacial Surgeons. J Oral Maxillofac Surg 47(8):834-42, 1989.

26. D’Eramo EM, Morbidity and mortality with outpatient anesthesia: The Massachusetts experience. J Oral Maxillofac Surg 57(5):531-6, 1999.

27. Dembo JB, Complications in anesthesia. In, Fonseca R, ed, Oral and Maxillofacial Surgery, 1st ed. WB Saunders, Philadelphia, 2000.

To request a printed copy of this article, please contact/ Tim Silegy, DDS, 6226 E. Spring St., #315, Long Beach, CA 90815.