Dr. James P. Zacny and colleagues’ January JADA article, "Preoperative Dental Anxiety and Mood Changes During Nitrous Oxide Inhalation," confirms the usefulness of analgesic nitrous oxide for treating anxious dental patients—an indication that has proved itself to be safe and effective over many years, provided the correct equipment and technique are used.1
It was, therefore, with some concern that I read in the article that "the initial concentration was determined largely on the basis of answers to questions related to alcohol use. For example, if a patient reported no alcohol use or very limited use ... the initial concentration was between 10 and 20 percent nitrous oxide ..." while with " ... more consistent or nightly alcohol consumption, the initial concentration was between 30 and 40 percent nitrous oxide ... ."
We and others have been using analgesic nitrous oxide for treating alcohol2,3 and other substance abuse withdrawal states4 for many years. Although there is cross-tolerance between alcohol and other substances of abuse and analgesic nitrous oxide,2–4 we have found that this cannot be used as a general guide for estimating the initial or, for that matter, the final dose of nitrous oxide to produce comfortable conscious patients when using nitrous oxide sedation.3
Indeed, in our work with alcohol withdrawal, we have found that a concentration as low as 15 percent nitrous oxide in oxygen2 can produce a good therapeutic effect even in heavy drinkers who could be classified as having alcohol dependence disorder.2,3
We and others1–4 therefore consider it important to slowly and carefully titrate the concentrations of nitrous oxide to the patient’s clinical requirements. One should not assume anything regarding the patient’s requirements based on his or her alcohol consumption or, indeed, on any other criterion except the patient’s response during titration.1–4
Careful titration avoids excessive sedation and/or dysphoria, which can, in some cases, produce excitation and even panic,1,2 the exact opposite of the goal of a relaxed patient. Such patients may avoid further exposure to the gas, thus preventing them from obtaining the benefits of competent nitrous oxide sedation during future treatments.
It also is not clear from the article whether a dental anesthesia or dental sedation flowmeter was used. This should be stated because it is our view that, under usual clinical conditions, conscious sedation with nitrous oxide should only be administered using custom-designed equipment having a built-in fail-safe device.1–4 The use of such equipment should be obligatory. Although the technique has an unrivaled safety record,1 it further enhances safety by reducing the likelihood of anesthesia and/or hypoxia.1–4 The use of the term "dental anesthesia machine"5 also confuses the concepts of anesthesia and analgesia, which are quite distinct states and which are far too often confused.4
It is for this reason that my colleague, F. J. Lichtigfeld, and I introduced the term "psychotropic analgesic nitrous oxide" so that it would be clear at all times that we were using a technique where the patient is conscious throughout administration of nitrous oxide for neuropsychiatric applications.4
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