chapter 12 Inhalation Sedation: Rationale
The technique of inhalation sedation with nitrous oxide (N2O) and oxygen (O2) possesses many significant advantages over other techniques of pharmacosedation. Inhalation sedation represents the most nearly “ideal” clinical sedative circumstance. This chapter discusses and demonstrates the indications for use of N2O-O2 in dentistry and other constantly expanding branches of medicine (Figure 12-1).
ADVANTAGES
1. The onset of action of inhalation sedation is more rapid than that of oral, rectal, intranasal (IN), or intramuscular (IM) sedation. The onset of action of intravenous (IV) medications is approximately, but not quite, equal to that of inhalation sedation.
2. Peak clinical effect does not develop in most techniques for a considerable time. Although variations do exist, peak clinical actions do not develop for most orally, rectally, intranasally, and intramuscularly administered drugs for a period of time that makes titration impossible. Only inhalation and IV drug administration provide peak clinical actions in a time span permitting titration. For the IV route, this time-to-peak effect varies with the drug administered, ranging from 1 minute to approximately 20 minutes (e.g., lorazepam).
3. The depth of sedation achieved with inhalation sedation may be altered from moment to moment, permitting the drug administrator to increase or decrease the depth of sedation. With no other technique of sedation does the administrator have as much control over the clinical actions of the drugs. This degree of control represents a significant safety feature of inhalation sedation.
4. The duration of action is an important consideration in the selection of a pharmacosedative technique in an outpatient. In situations in which a sedation technique has a relatively fixed duration of clinical activity, dental treatment must be tailored to this, whereas in those techniques with a flexible duration of action, the planned procedure may be of any length (e.g., a minute or so for the taking of radiographs or 3 to 4 hours [or longer] for preparation and impression of multiple abutments for fixed bridgework).
| Oral | Fixed duration of action, approximately 2 to 3 hr |
| Rectal | Fixed duration of action, approximately 2 to 3 hr |
| IM, IN | Fixed duration of action, approximately 2 to 4 hr, with significant variation by drug |
| IV | Fixed duration of action, with significant variation by drug Diazepam, midazolam, 45 min Promethazine, 90 min Pentobarbital, 2 to 4 hr |
| Inhalation | Duration variable, at discretion of administrator |
5. Recovery time from inhalation sedation is rapid and is the most complete of any pharmacosedation technique. Because N2O is not metabolized by the body, the gas is rapidly and virtually completely eliminated from the body within 3 to 5 minutes. In all other techniques, the recovery from sedation is considerably slower.1
| Oral | Recovery not entirely complete even after 2 to 3 hr |
| Rectal | Recovery not entirely complete even after 2 to 3 hr |
| IM, IN | Recovery not entirely complete even after 2 to 3 hr |
| IV | Recovery not entirely complete even after 2 to 3 hr |
| Inhalation | Recovery usually complete following 3 to 5 min of inhalation of 100% O2 |
6. As discussed, titration is the ability to administer small, incremental doses of a drug until a desired clinical action is obtained. In my opinion, the ability to titrate a drug represents the greatest safety feature a technique can possess because it permits the drug administrator virtually absolute control over the actions of the drug.2 Significant drug overdose will not develop in techniques in which titration is possible as long as the administrator does indeed titrate the drug.
7. In an outpatient setting, it is advantageous for the patient to be discharged from the office following a procedure with no prohibitions on activities. Unfortunately, because all of the drugs administered for the reduction of fear and anxiety are central nervous system (CNS) depressants, the patient may not be permitted to leave the office unescorted to operate a motor vehicle or to perform tasks requiring mental alertness for a number of hours following the administration of these drugs.3 To do so is to increase the potential risk to both the patient (physical risk) and the dentist (legal risk). Recovery must be complete, with absolutely no doubt in the mind of the dentist that the patient is able to function normally; if not, the patient should not be permitted to leave the office unescorted.
| Oral | Recovery not complete; patient always requires escort |
| Rectal | Recovery not complete; as usually used in pediatric dentistry, patient will be escorted by parent or guardian |
| IM, IN | Recovery not complete; patient always requires escort |
| IV | Recovery not complete; patient always requires escort |
| Inhalation | Recovery almost always complete; patient usually may be discharged from office alone, with no admonitions about activities |
8. No injection is required for the administration of inhalation sedation. (Local anesthesia is still necessary.)
9. Inhalation sedation with N2O-O2 is safe. Very few side effects are associated with its use, as described in the following chapters.
10. The drugs used in this technique have no adverse effects on the liver, kidneys, brain, or cardiovascular and respiratory systems.
11. Inhalation sedation with N2O-O2 can be used instead of local anesthesia in certain procedures. N2O does possess analgesic properties when given in the usual sedative concentrations. The analgesia produced by a 20% concentration of N2O is equivalent to that of 10 to 15 mg of morphine. However, the degree of analgesia is quite variable from patient to patient and therefore cannot be relied on to provide all of the pain control required for a procedure. Certain procedures, such as those involving soft tissues (scaling, curettage), may be performed in many instances without using local anesthesia.
Disadvantages
The following are disadvantages associated with N2O-O2 inhalation sedation.
3. The equipment required for inhalation sedation occupies considerable space within the dental surgery suite. Placed in the usual small dental surgery office, a portable N2O-O2 unit can be quite cumbersome.
4. N2O is not a potent agent. When it is used in combination with at least 20% O2, there will be a small percentage of patients in whom the technique will fail to produce the desired clinical actions. In no circumstance should N2O ever be administered with less than 20% O2. Inhalation sedation units available in the United States are designed so that they will not deliver less than 30% O2, with a maximum limit of 70%. N2O inhalation sedation with N2O-O2 is not a panacea. Failures will occur primarily because of the lack of potency of the agent or due to the administration and/or titration technique.
5. A degree of cooperation is required from the patient. For inhalation sedation to be effective, the patient must be able to inhale the gases through either the nose or the mouth. Should the patient be unable or unwilling to do so, clinical failure will result.
6. All members of the sedation team employing N2O-O2 must receive training in its safe and effective use. Ideally, this training is acquired in dental, dental hygiene, or dental assisting school. Postgraduate continuing education courses are also available, but quality varies tremendously in these programs. The guidelines established by the American Dental Association (ADA), the American Dental Society of Anesthesiology (ADSA), and the American Dental Education Association (ADEA) recommend not less than 14 hours of training, including treatment of dental patients receiving inhalation sedation (see Chapter 19).4
INDICATIONS
The primary indications for the use of inhalation sedation are the same as those for other sedative techniques: the management of fear and anxiety, the medically compromised patient, and the management of gagging.5 Over and above these usual indications, N2O-O2 is readily controllable; this permits its use for aspects of dental care in which the use of moderate sedation might not usually be considered.
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