V. Technique for Administering Nitrous Oxide Conscious Sedation

The following is a suggested "step by step" technique for administering nitrous oxide - oxygen conscious sedation. Techniques may vary slightly from patient to patient, as each patient is an individual with different responses to different types and levels of stress. The same patient may respond differently from day to day depending on emotional conditions. Changes in medical or physical conditions, or drugs and medications the patient may be taking, can also make a substantial difference in patient reaction to nitrous oxide. Therefore, it is important to always reassess the patients physical and emotional state, as well as review all drugs the patient may be taking prior to each nitrous oxide administration.

A. Pre-induction Considerations

Before administering N2O-O2 Conscious Sedation:

1. Eating prior to receiving N2O is acceptable, but only a light meal. If the patient becomes nauseated easily (for example tends to get "car sick" or "air sick"), consider having the patient refrain from eating.

2. Many dentists permit patients who have had N2O sedation to leave the office unaccompanied, and to drive an automobile or operate potentially dangerous machinery. Jastak and Orendurff1 in their study to test driving safety following N2O - O2 sedation found most subjects show adequate recovery to drive in 5 minutes, but one subject (of 19 studied) required additional recovery time. The maximum duration of time in the study was 30 minutes, and all subjects were young healthy volunteers that did not undergo dental treatment. The authors noted that patients who have undergone stressful treatment or receive N2O for longer than 30 minutes may require more time for recovery. In a more recent study, Conry, et. al2 subjected volunteers to 90 minutes of N2O levels sufficient to produce subjective symptoms. They concluded that following 90 minutes exposure, psychomotor function impairment continued to be detectable 10 minutes after termination of treatment, and probably continued longer. At the same time, they detected no impairment of vigilance, immediate memory or mental tracking ability.

Occasionally, for no apparent reason, patients seem to recover much more slowly from N2O. Therefore, the wisest precaution would be to require the patient be accompanied by a responsible adult who can take responsibility for seeing the patient home safely. When this is not practical, the patient should be asked, and be prepared to remain under observation in the office for at least an additional 20 minutes, or more, and be released only when all effects of the N2O appear to be gone. The bottom line issue is, if the patient has an accident, there is no way to prove beyond all doubt that the N2O was not a contributing factor.

An additional precaution, and one that may be an aid legally, is the Trieger Test. Trieger test imageTrieger Test This test would be administered both preoperatively and postoperatively. Once the postoperative drawing matches the preoperative drawing, the patient should be considered recovered well enough to leave your office.

3. If it is the first N2O experience for the patient, describe the benefits and obtain "informed"consent.

4. Check the equipment daily before the first patient receives nitrous oxide. Be sure the tanks are turned on and contain sufficient gas for the procedure. Check the machine for proper function and gas flow. Check the calibration of any machine that provides a dial for regulating the percentage of gases being delivered. Most machines guarantee an accuracy of plus or minus five percent. Insure that the fail-safe is working and the machine will cut off the N2O in the event that the O2 supply is lost. Check to see that the O2 flush valve, the air inlet valve and the non-rebreathing valve are all functioning properly.

B. Pre-induction - Patient Considerations

1. It is important to establish a good rapport, especially with the apprehensive patient. The patient must have confidence in the dentist and the technique of N2O. Malamed3 suggests introducing the patient to N2O at an appointment prior to the one in which the stressful procedure is to be done. This permits the apprehensive patient to become familiar with the nasal hood, the smells and effects of N2O in a relaxed, non-threatening atmosphere.

2. When discussing N2O with patients, describe the technique in terms the patient can understand. Stress the positive features of N2O but don't oversell or promise a successful outcome. (Some patients don't respond well, and may reject it.) Certainly, never coerce or force a patient (including pediatric patients) to receive N2O. An unpleasant result is almost assured for an unwilling recipient. If the patient enters treatment with the expectation of success, he likely will achieve it, and vice-versa.

3. Patients must understand the objective of N2O is relaxation and sedation and not anesthesia or sleep! It may be compared to a couple of beers or cocktails but with no hangover and a quick recovery. However, if referral to alcoholic beverages offends the patient because of religious or personal beliefs, it may make them reluctant to try it, and some other comparison should be used. It has been suggested that recovering alcoholics should not be given N2O because the euphoria that can accompany N2O may lead to a desire to return to alcohol.

4. Loosen tight clothing such as ties and collars. The patient should remove contact lenses.

5. Provide quiet relaxing surroundings for the patient. Avoid discussing difficulties with the assistant when the patient can hear you.

6. Recheck the medical history for any change; specifically determine if there has been any change in drugs the patient may be taking. Also take a moment to "read" the patient's physical and emotional state that particular day prior to starting N2O.

7. Suggest the patient visit the restroom prior to starting N2O. This should prevent the possible interruption of treatment, oxygenating the patient and then re-inducing the patient to resume treatment, all of which can take 10 or more minutes.

SUGGESTED PRE-INDUCTION ROUTINES

C. Initial Inducement

1. Place patient in a SEMISUPINE position.

2. Obtain preoperative baseline blood pressure and pulse.

3. Turn on 100% O2....6-8 liter flow; the normal range for most adults. (Always begin and end with 100% oxygen) Pre oxygenation is to establish flow rates and some "comfortability" and to diminish anxiety. It will increase saturation some but is unnecessary for this reason.

4. Place the hood over patient's nose and have the patient adjust for a snug but comfortable fit...check for leaks.

5. Establish a proper flow rate for the patient by observing the expansion of the bag.

6. Maintain personal contact with patient (verbal and/or tactile) throughout the procedure.

7. Introduce N2O gradually, start with 20-25% N2O, 75-80% O2.

8. Make suggestions to patient that are pleasant and relaxing. This effort can make the experience successful; your assistant may be better at this than you.

9. After 2-3 minutes, increase N2O concentrations in stages to the desired effect -but not exceeding a maximum, in most cases, of 50% (30% - 40% N2O is usually sufficient). The patient should breathe a given level for 3-5 minutes before increasing the concentration to the next higher level.

10. Continue to monitor the patient, but do not allow the patient to talk excessively...(also monitor the machine).

11. Reduce N2O mixture to the lowest percentage with which the patient is comfortable. Near end of procedure cut off N2O and give 100% O2.

12. In Texas, the dentist can not leave the operatory while the patient is receiving N2O unless the hygienist or assistant present in the operatory has passed the Texas State Board N2O certification test. The dentist may leave the room if O2 only is being administered. This, of course, may vary in different states; so each state's requirements must be reviewed.

13. Post oxygenate for 3-5 minutes, or longer if the patient exhibits continued signs of N2O effects.

14. Upright the chair slowly, and keep in the patient in the sitting position for a few minutes before allowing to get up out of the chair.

15. Obtain post operative blood pressure and pulse.

16. Always compliment the patient on how well he or she performed.

17. If unaccompanied, the patient should remain in the office for an additional 20 minutes after completion of oxygenation, or longer if the patient can still feel the effects of N2O.

D. Comments

1. 50-50 is average maximum...for most patients 30-40% N2O is sufficient, and many patients do well with only 25-35% N2O.

2. A few patients may tolerate higher percentages, but generally most complications develop above 50% N2O. If you feel greater than 50% N2O is necessary to obtain the desired affect, consider using another form of patient sedation such as oral sedation.

3. At higher altitudes, somewhat higher percentages may be required.

RECORDS

Keeping accurate records of each N2O administration can be extremely helpful. For example, if after administration, it is noted that a certain patient does well on 35% N2O, time and N2O can be saved by going to that percentage and not giving more than is necessary. This does not mean that titration is not necessary for each patient each administration time, as the patient's needs and emotional state may vary from day to day; but, in general, one can expect to titrate near the same percentage each administration. In addition, records are invaluable in defense of a possible malpractice threat.

Records of the N2O administration are kept as a part of the regular patient's record. The following information should be retained:

DISINFECTION OF EQUIPMENT

Nitrous oxide, like most inhalation anesthetic agents, are capable of depressing protective mechanisms, and thus increasing the incidence of respiratory disease. The rubber or plastic goods, such as the nasal hood, which have come in contact with the patient or the patient's exhaled breath become contaminated and must be disinfected before using again for another patient. Rubber goods are now on the market that are autoclavable; expensive but reuseability and a much improved method for preventing cross contamination makes the expense tolerable. Gas sterilization is also an alternative, but expensive. Chemical disinfection is still a choice, however, concern is surfacing that respiratory irritation following chemical disinfection may be present. It is very important, therefore, that all the equipment is rinsed thoroughly and allowed to dry before reuse.

Simply follow the autoclaving instructions that will be included with the equipment when autoclaving the rubber and scavenging system. According to Yegiela et al4, to chemically disinfect, perform the following: After each use, wash the nasal hood with soap and water to remove gross debris, and soak for 10 minutes in 2% glutaraldehyde. Rinse thoroughly with tap water and allow to dry. Yegiela also suggests weekly sterilizing all tubing, reservoir bags, and nasal hoods by storing them in glutaraldehyde for 10 hours, followed by rinsing in warm tap water for 1 hour.

Disposable nasal masks are available, often given to the patient or saved in the office for their next appointment. This eliminates cross contamination problems, but additional expense must obviously be absorbed somewhere. Nasal mask inserts are also an option from some manufactures. These inserts can be removed from the nasal masks after each patient and autoclaved or disinfected as suggested above.

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