12: Inhalation Sedation: Rationale

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).


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.

Oral 30-min onset
Rectal 30-min onset
IM, IN 10- to 15-min onset
IV 20-sec onset (approximate arm-to-brain circulation time); 1 to 2 min for clinical actions to develop
Inhalation <20 sec pulmonary circulation to brain time; 2- to 3-min onset for clinical actions to develop

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.

Oral 60-min peak action
Rectal 60-min peak action
IM, IN 30-min peak action
IV 60-sec to 20-min peak action
Inhalation 3- to 5-min peak action

Oral Cannot easily deepen or lighten sedation
Rectal Cannot easily deepen or lighten sedation
IM, IN Cannot easily deepen or lighten sedation
IV Sedation level may easily be deepened; however, lessening of sedation is difficult to achieve
Inhalation Sedation levels easily changed either way

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.

Oral Titration not possible
Rectal Titration not possible
IM, IN Titration not possible
IV Titration possible
Inhalation Titration possible

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


The following are disadvantages associated with N2O-O2 inhalation sedation.


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.

Many procedures that are generally considered nonthreatening or even innocuous might, however, prove to be extremely traumatic to some patients. Many of these procedures lend themselves quite readily to the use of N2O-O2.

Jan 5, 2015 | Posted by in General Dentistry | Comments Off on 12: Inhalation Sedation: Rationale
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