Induction techniques for nitrous oxide/oxygen sedation
Dr. Fred Quarnstrom reviews various nitrous oxide sedation techniques including rapid induction.
By Fred C. Quarnstrom, DDS, FADSA, FAGD, FICD, FACD, CDC, FACD
We all learned how to administer nitrous oxide sedation in dental and dental hygiene school. However, in many cases, the introduction to the subject was so complex or time-consuming that dental professionals simply do not use nitrous oxide sedation or are uncomfortable because they really do not understand the process.
Nitrous oxide sedation is one of the safest sedatives we can use. It has rapid uptake, good effect, and recovery is very rapid. Following nitrous oxide sedation, patients can drive themselves home after a short period of time. It can be used safely on patients with almost all medical conditions — COPD (chronic obstructive pulmonary disease) being one contraindication.
It is also best to avoid using nitrous oxide sedation with patients who are pregnant. I believe any dentistry should be avoided on pregnant patients. I once had a patient tell me as I was about to start a bridge prep appointment that she was spending her whole day in doctors’ offices. I asked what she meant by that. She explained that she was three months pregnant and had been spotting. I stopped and explained that I did not think we should do the bridge prep that day. The patient had a miscarriage that evening. Had I treated her, we would always have wondered if the dentistry or nitrous oxide had been the cause of her spontaneous abortion. Aside from these exceptions, most patients — including heart patients — are protected by the high levels of oxygen and the sedation of the nitrous oxide. The question usually is, “Is the patient healthy enough to receive dental care?” If the answer is, “Yes,” then the patient probably can use nitrous oxide oxygen sedation safely.
Many of us were taught that you must first put the patient on 100% oxygen for five minutes. This thinking came from the medical anesthesia community. Many surgery patients are intubated immediately after being put to sleep under general anesthesia. To do this, the patient is paralyzed for a few minutes. During that time the anesthesiologist must breathe for the patient. For 10 to 15 seconds, there may be no air exchange as the endotracheal tube is placed into the trachea. It is important that the patient be saturated with oxygen during this time.
In dentistry we do not intubate patients when using nitrous oxide sedation, nor do we paralyze our patients. So there is no reason to pre-oxygenate. Others suggest we should have the patient on 100% oxygen to determine their minute volume, the number of liters of oxygen or combination of gas they breathe every minute. The number of breaths taken each minute multiplied by the size of each breath will give this number. For most adults, it is close to 6 liters per minute, 12 breaths per minute, and 500 cc per breath.
Watching a patient breathe for five minutes and slowly increasing the volume of gas until the reservoir bag does not completely empty or overfill takes time. It is more efficient to turn on a mixture that will give appropriate sedation: 25% to 35% nitrous oxide and 65% to 75% oxygen. Watch the bag — if it empties, turn up the volume; if it overfills, turn down the volume. While doing this, ask the patient to raise a hand when he or she first feels the initial effects of nitrous. Ask a minute later if the patient is relaxed or needs to be more relaxed. Change the concentration of gas to achieve the desired sedation. All of this takes a minute or maybe two minutes at the most.
Once you know what level is appropriate, use that minute volume and concentration as a starting point for future appointments. You may need to increase or decrease volume or concentrations depending on the procedure being preformed and the patient’s frame of mind. However, adjustment will be minimal.
If you want a more rapid induction, have the patient take three breaths of a 70% nitrous oxide/oxygen gas mixture and then turn the concentration down to 30% nitrous oxide. Almost all patients will be relaxed in a matter of 30 seconds or less. You do want to empty the bag after the third breath so it fills with the 30% mixture. In this way you can achieve sedation very quickly. There is no reason to leave a patient on nitrous while you wait for local anesthesia to take effect or if you need to leave the room.
One final comment — It is imperative that a patient never be left alone in an operatory while on nitrous oxide sedation. Should the patient decide to get out of the chair, he or she could fall because coordination is impaired. A dentist should always be accompanied by a second staff member when treating a patient on nitrous because some patients have sexual hallucinations while on nitrous oxide, but that is a topic for some future presentation.
A demonstration of these induction techniques can be seen on a podcast of the international dental forum: http://pages.wizzard.tv/e/k-971be16f7ccb95f5
Fred C. Quarnstrom, DDS, FADSA, FAGD, FICD, FACD, CDC, FACD, graduated from the University of Washington Dental School in 1964 and started his dental career as a dental officer in the United States Navy. He served with the Marine Corps and a Naval Construction Battalion, making the first amphibious assault in Vietnam at Chu Lai. After the Navy experience, he spent a year at the Washington Hospital Center in Washington, DC, in the first year of a medical residency in anesthesia. He has received fellowships in the Academy of General Dentistry, American Dental Society of Anesthesiology, International College of Dentistry, and the American College of Dentistry. He is a diplomate of the American Board of Dental Anesthesiology and the National Board of Dental Anesthesiology. He is a certified dental insurance consultant of the American Association of Dental Consultants. He has presented more than 500 continuing-education courses on nitrous oxide sedation, practice management, computer usage, electronic dental anesthesia, and IV and Halcion oral sedation. He holds the position of clinical assistant professor in the Department of Dental Public Health Sciences at the University of Washington School of Dentistry and the Faculty of Dentistry University of British Columbia. He has authored 45 papers, three manuals, two chapters in books, a book for dental consumers titled “Open Wider: Your Wallet Not Your Mouth, A Consumer’s Guide to Dentistry,” and continues to do research in nitrous oxide sedation, electronic dental anesthesia, and Halcion oral sedation. He has been in a private general practice in Seattle since 1967. Contact him at http://faculty.washington.edu/quarn and http://openwider.org, or by e-mail at email@example.com.