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36 Dental Tribune Middle East & Africa Edition | May-June 2015pediatric tribune > Page 45 Current guidelines for the use of nitrous oxide inhalation analgesia/anxiolysis in pediatric dentistry By Dr. Manal Al Halabi, UAE A bstract Nitrous oxide/oxygen in- halation analgesia and an- xiolysis as a behavioral manage- ment intervention in children has maintained an excellent safety record and is, therefore, utilized widely by pediatric den- tists. As is true of any diagnostic or therapeutic dental interven- tion, however, its usage merits periodic review, especially when it is routinely applied. When ni- trous oxide/oxygen is used in combination with other seda- tives, such poly-pharmacy can produce potentially serious side effects. Bioenvironmental risks to patients and staff can be en- countered if proper use of the gas and appropriate dispensa- tion of exhaled nitrous oxide is not monitored. Using historical publications, current empirical articles, professional usage poli- cies, and educational textbooks, the purpose of this article was to review indications and con- traindications of nitrous oxide/ oxygen inhalation analgesia and anxiolysis and discuss vari- ous factors that should or should not be considered about its use. Even though today’s parents may be more accepting of phar- macologic approaches such as nitrous oxide, the choice to use it should always be made with the child’s best interest in mind and with adequate training and understanding. Introduction After the analgesic qualities of nitrous oxide were determined in the 19th century, dental prac- titioners experimented with nitrous oxide as a general anes- thetic for almost a century, fre- quently pushing beyond physi- ologic tolerance levels. Its usage then shifted to that of an analge- sic and subsequently to an inha- lation sedative. The significantly reduced dosages needed to elicit sedation rendered the drug much safer and enabled dentists to administer nitrous oxide with ever-greater frequencies. Con- sequently, by the dawn of the 21st century, N2O had become a routine component of dental care among many dentists. Nitrous oxide/oxygen inhalation is considered a safe and effec- tive technique to reduce anxiety, produce analgesia, and enhance effective communication be- tween a patient and health care provider. The essential need to properly diagnose and treat, as well as the safety of the patient and practitioner, should be care- fully measured before using nitrous oxide1 . In medicine, ni- trous oxide has long been used as an inhalation anesthetic for both the induction and main- tenance of general anesthesia. More recently, nitrous oxide protocols have been established for pediatric patients undergo- ing diagnostic procedures such as computer tomography, en- doscopy, electroencephalogra- phy and bone marrow biopsies2 . All children should be able to expect painless, high quality dental care. While anxiety and pain can be modified by behav- ior management psychological techniques, additional pharma- cological approaches may be necessary. Analgesia/anxioly- sis is defined as diminution or elimination of pain and anxiety in a conscious patient2 . The pa- tient responds normally to ver- bal commands. All vital signs are stable, there is no significant risk of losing protective reflexes, and the patient is able to return to pre-procedure mobility. In children, analgesia/anxiolysis may be helpful to expedite the delivery of procedures that are not particularly uncomfortable, but require that the patient not move3 . By reducing or reliev- ing anxiety, the patient may be able to tolerate unpleasant pro- cedures, discomfort, or pain. The outcome of any pharmaco- logical approach especially mild ones is variable and dependent upon patient’s response to dif- ferent drugs. The clinical effect of nitrous oxide/oxygen inhala- tion, however, is relatively more predictable among the majority of the population. Mechanism of action Nitrous oxide is a colorless and nearly odorless gas with an in- distinct, sweet smell. It is an effective analgesic/anxiolytic agent producing central nervous system (CNS) depression and euphoria with slight effect on the respiratory system3 . Nitrous oxide has multiple mechanisms of action. The analgesic effect of nitrous oxide appears to be initiated by endogeneous opioid peptides release from neurons which results in activation of opioid receptors and descend- ing Gamma-aminobutyric acid type A (GABAA) receptors and noradrenergic pathways that modulate nociceptive process- ing at the spinal level. The an- xiolytic effect involves activation of the GABAA receptor both di- rectly and indirectly through the benzodiazepine binding sites4,5 . Nitrous oxide demonstrates rap- id uptake, it is absorbed quickly from the alveoli and held in a simple solution in the serum. It is relatively insoluble, passing down a gradient into other tis- sues and cells in the body, such as the CNS. It is excreted quickly from the lungs. As nitrous oxide is 34 times more soluble than nitrogen in blood, diffusion hy- poxia may occur. Studies have shown that chil- dren desaturate more rapidly than adolescents, and adminis- tering 100 percent oxygen to the patient once the nitrous oxide has been terminated is impor- tant6 . Nitrous oxide causes slight depression in cardiac output though peripheral resistance is marginally increased, thereby sustaining the blood pressure3 . This is of particular advantage while handling patients with cerebrovascular system disor- ders. Nitrous oxide is absorbed quick- ly, allowing for both rapid on- set and recovery (two to three minutes). It causes negligible impairment of any reflexes, thus protecting the cough reflex3 . It exhibits a superior safety pro- file with no recorded fatalities or cases of serious morbidity when used within recommend- ed concentrations7 . Studies have reported negative outcomes as- sociated with use of nitrous ox- ide greater than 50 percent and as an anesthetic during major surgery8 . Although rare, silent regurgitation and subsequent aspiration need to be considered with nitrous oxide/oxygen seda- Class I Class II Class III Class IV Class V No organic, physiological, biochemical or psychiatric disturbance. Mild to moderate systemic disturbance, e.g. mild diabetes, moderate anemia, well-controlled asthma, not disabling. Severe systemic disease, e.g. severe diabetes with vascular complications, severe pulmonary insufficiency, disabling. Severe systemic disorders that are already life threatening, e.g. signs of cardiac insufficiency. The moribund patient who has little chance of survival without operative intervention. Table 1. ASA Classification. American Society of Anesthesiologists. tion. The concern lies in wheth- er pharyneal-laryngeal reflexes remain intact. This problem can be avoided by not allowing the patient to go into an uncon- scious state9 . Nitrous oxide has been associ- ated with bioenvironmental concerns because of its contri- bution to the greenhouse effect. Bacteria in soils and oceans emit nitrous oxide naturally; it is pro- duced by humans through the burning of fossil fuels and for- ests and the agricultural prac- tices of soil cultivation and ni- trogen fertilization. Altogether, nitrous oxide contributes about five percent to the greenhouse effect11 . Only a trivial fraction of this five percent (0.35 to two per- cent), however, is actually the result of combined medical and dental applications of nitrous ox- ide gas11 . The decision to use nitrous oxide/oxygen inhalation anal- gesia Nitrous oxide/oxygen inhalation analgesia should be offered to children with mild to moderate anxiety to enable them to accept dental treatment better and to facilitate coping across sequen- tial visits. The decision to use nitrous oxide/oxygen analgesia/ anxiolysis must always utilize alternative behavioral guidance modalities, the patient’s dental requirements, the effect on the quality of dental care, the pa- tient’s emotional development, and the patient’s physical con- siderations. Nitrous oxide gener- ally is acceptable to children and can be titrated easily. Most chil- dren are enthusiastic about the administration of nitrous oxide/ oxygen; many children report dreaming, floating or being on a “space-ride”9 . For some patients, however, the feeling of “losing control” may be troubling and patients suffering from claustro- phobia can find the nasal hood restraining and disagreeable10 . Fitness for nitrous oxide/oxy- gen inhalation analgesia Review of the patient’s medical history should be performed pri- or to the decision to use nitrous oxide/oxygen analgesia/anxi- olysis. This assessment should include: 1. Allergies and previous allergic or adverse drug reactions. 2. Current medications includ- ing dose, time, route, and site of administration. 3. Diseases, disorders, or physi- cal abnormalities and pregnan- cy status. 4. Previous hospitalization to in- clude the date and purpose. 5. Recent illnesses (eg, cold or congestion) that may compro- mise the airway. Children who are ASA I or II (Table 1) can be deemed fit to undergo nitrous oxide/oxygen inhalation sedation in general, community or specialist (pedi- atric) practice. Those who are not in these categories requir- ing conscious sedation should be treated in a hospital environ- ment with due consideration to their individual needs and medi- cal condition, involving the as- sistance of medical colleagues where appropriate12 . The objectives of the Use of ni- trous oxide/oxygen inhalation analgesia The objectives of nitrous oxide/ oxygen inhalation include: 1. Reduce or eliminate anxiety. 2. Reduce untoward movement and reaction to dental treatment. 3. Enhance communication and patient cooperation. 4. Raise the pain response threshold. 5. Increase acceptance for long- er appointments. 6. Aid in treatment of the men- tally/physically disabled or med- ically compromised patient. 7. Reduce gagging. 8. Potentiate the effect of seda- tives. Disadvantages of nitrous ox- ide/oxygen inhalation analge- sia: Disadvantages of nitrous oxide/ oxygen inhalation may include3 : 1. Weak potency. 2. Significant dependence on psychological reassurance. 3. Interference of the nasal hood with injection to anterior maxil- lary region. 4.Patientmustbeabletobreathe through the nose. 5. Nitrous oxide pollution and potential occupational exposure health hazards. Indications for the use of ni- trous oxide/oxygen inhalation analgesia Indications for use of nitrous ox- ide/oxygen analgesia/anxiolysis include: 1. A fearful, anxious, or disrup- tive patient. 2. Certain patients with special health care needs. 3. A patient whose gag reflex in- terferes with dental care. 4. A patient for whom profound local anesthesia cannot be ob- tained.