chapter 16 Inhalation Sedation: Complications
Complications with nitrous-oxygen are rare indeed; however, there is no technique that does not have the potential for complications. Complications with nitrous oxide (N2O) almost have to be intentional because this form of sedation is extremely safe. The usual cause is inadequate or incomplete training. Combining N2O with one or more other sedative agents can cause oversedation. N2O is forgiving in that most issues that arise are quickly corrected by proper technique. Complications include the following:
First, inadequate or incomplete sedation usually involves poor patient selection for the use of nitrous oxide-oxygen (N2O-O2) sedation. An example would be the authoritarian type of personality, who when faced with the prospect of loss of control or the sense of this loss becomes uncomfortable. The patient, not wanting to lose control, will consciously or subconsciously fight the effects of the agent (N2O). Unfortunately, other similar sedative procedures produce the same effects, and the success rate of most will be poor in the authoritarian type of patient unless more potent agents are used.
Patients who are emotionally or psychologically unstable may not fare well with N2O-O2. Patients who use mind-altering drugs may also have residual conflicting or counterproductive effects from N2O administration. These patients, particularly if chronic abusers, may be “resistant” to the effects of N2O and/or expect or require a level of potency that is beyond the capacity of N2O in therapeutic percentages. Hyporesponders, representing approximately 15% of the population, may not respond to the highest levels of N2O that can possibly be given (70% concentration). N2O-O2 use is also not intended for severely fearful patients. Choose your patient carefully and be mindful that N2O-O2 works best in conjunction with local anesthetic.1
The second classification of potential complications—poor patient experience—can be best managed by prevention. Prevention is most easily and best accomplished by titration of the N2O during administration. Titration allows for enough N2O to be given to achieve the desired clinical effect for a given patient for a particular procedure. Most patients who have complications are oversedated. Physical signs and symptoms such as excessive perspiration, nausea and vomiting, hallucinations, expectoration, and increased agitation rather than sedation are all clear signs and symptoms of oversedation. If a patient exhibits any of these signs, the N2O concentration should be decreased, and in a very short time, a reversal of these adverse reactions will be evident and the patient’s status returned to normal. It is truly impressive to observe how quickly a patient will return to a level of cooperation and acceptance of treatment after this decrease in N2O concentration. It is important to keep the oxygen (O2) flow unchanged. The built-in features of modern inhalation sedation units prevent a flow with more than 70% N2O from occurring. This safety feature helps reduce the possibility of oversedation and possible hypoxia.
The primary reason to administer N2O-O2 is to provide a pleasant experience for the patient by altering his or her mood. Anything less is unacceptable. Some patients can have an inexplicable idiosyncratic reaction to a drug, but this is extremely rare with N2O, and there are no true outright contraindications, only relative contraindications. The relative contraindications of N2O-O2 are discussed in Chapter 12.
The last classification of potential complications is equipment performance. This has become more rare as a result of the intense scrutiny placed on manufacturers by numerous professional agencies and the extreme desire by the manufacturers to provide a safe and excellent product. The manufacturers have succeeded in providing a safe machine with backup systems that ensure that adequate levels of O2 are present to maintain operation. Even with a failure in the O2 supply, the machine still allows the patient to receive room air without impediment. The possibility for machine or equipment failure usually revolves around purposeful alteration of the equipment as sold or the use of outdated equipment. The rubber parts of the sedation machine can tear, leak, or malfunction and should therefore be frequently inspected per the American Dental Association’s protocol. The chance of equipment failure in today’s environment is extremely small. Equipment failure can best be prevented by routine examination and inspection of the inhalation sedation unit.
Potential complications, as mentioned, rarely occur. When a complication does arise, it is commonly the result of a high concentration of N2O (greater than 50%) and long duration of use (greater than 1 hour).
The incidence of nausea and vomiting with the administration of N2O-O2 inhalation sedation is very low. Nausea and vomiting occur in the sedation arena as a result of hypoxia or oversedation. N2O was historically administered without the addition of supplemental O2. The “technique” was to create an intentionally hypoxic (cyanotic) patient and then work as rapidly as possible until the patient recovered. Some patients did not recover; some woke up very nauseated and vomiting. This history has in some ar/>