Sedação consciente com óxido nitroso em clínica odontológica: principais indicações e segurança / Concious sedation with nitrous oxide in dental clinics: main indications and safety

A ansiedade desempenha um papel significativo na experiência de tratamentos odontológicos e pode resultar em evasão por parte dos pacientes. Isso é especialmente relevante para grupos como pacientes pediátricos e aqueles com necessidades especiais, que muitas vezes requerem técnicas de controle de comportamento ou sedação devido à ansiedade. No entanto, a ansiedade não deve ser negligenciada mesmo em pacientes sem odontofobia grave, pois está relacionada à percepção da dor durante os procedimentos odontológicos. A sedação consciente com óxido nitroso surge como uma alternativa valiosa para reduzir a ansiedade e melhorar o conforto do paciente. Ao contrário dos benzodiazepínicos e da anestesia geral, o óxido nitroso atua no sistema nervoso de uma forma que deprime levemente o córtex cerebral, sem afetar o centro respiratório. Isso permite o uso de concentrações subanestésicas do gás, administradas com oxigênio por meio de uma máscara nasal. O óxido nitroso é de rápida ação, pouco solúvel e tem um período de recuperação breve, permitindo que os pacientes retornem rapidamente às atividades normais. Este estudo, uma revisão de literatura, explora o mecanismo de ação do óxido nitroso, suas indicações na prática odontológica e examina possíveis riscos e contraindicações associados ao seu uso. Em resumo, a sedação consciente com óxido nitroso se mostra como uma opção promissora para aliviar a ansiedade e melhorar a experiência de tratamentos odontológicos, beneficiando uma ampla gama de pacientes, não apenas aqueles com fobias graves.

Anxiety, in an outpatient dental environment, plays a fundamental role in pain and discomfort expectation, resulting in increase of treatment evasion. The groups that present greater difficulty in cooperation are children and special needs patients, with behavioral control and sedation being often necessary. Nevertheless, literature emphasizes that anxiety must be evaluated as a critical stage and its management done not only in patients with elevated anxiety levels, but being crucial on pain control of every dental patient, since higher grades of restlessness equals higher pain perception. It is known that the use of nitrous oxide in conscious sedation proves to be an useful tool on reducing anxiety and enabling comfortable interventions, indicating that it is an alternative to the use of benzodiazepines and general anesthesia. The drug acts on the nervous system, promoting a slight depression of the cerebral cortex and, unlike benzodiazepines, which act at the medulla level, it does not depress the respiratory center. The technique uses sub-anesthetic concentrations of nitrous oxide delivered with oxygen through a nasal mask. Nitrous oxide is poorly soluble and has a rapid onset of action, being therefore associated with a rapid recovery period. The duration of sedation is controlled and the patient can quickly return to normal activities. This paper is a narrative review with the objective of exploring the mechanism of action of this gas, evaluating its indications for use in dental clinic and verifying possible risks and contraindications.

Uso de óxido nitroso como sedação consciente por profissionais de odontologia no Rio Grande do Sul: um estudo transversal / Prevalence of nitrous oxide use as conscious sedation by dentistry professionals in Rio Grande do Sul: a cross-sectional study

Objetivo: Avaliar fatores associados, percepção e prevalência do uso de óxido nitroso por cirurgiões-dentistas do Rio Grande do Sul, Brasil. Metodologia: Realizou-se um estudo transversal, de base eletrônica, com profissionais registrados no Rio Grande do Sul. A coleta de dados baseou-se no envio, por e-mails e campanhas no Instagram, de um questionário via plataforma Google Forms contendo 27 questões acerca do uso de óxido nitroso em atendimentos odontológicos, bem como o perfil e as percepções dos profissionais sobre a técnica. Resultados: Dos 220 participantes, apenas 12,3% utilizava o óxido nitroso em sua prática clínica, sendo as especialidades que mais utilizavam, cirurgia e odontopediatria. Dentre os que reportaram utilizar a técnica, 81,5% tinham mais de 29 anos (p<0,001) e possuíam curso de pós-graduação, sendo que destes, 55,6% realizou o curso de habilitação (p<0,01) e mais da metade (55,6%) relatou utilizar em pacientes adultos (p<0,001). O alto custo do equipamento, bem como a falta de interesse dos profissionais, foram as principais razões para o não uso da técnica. Conclusão: A técnica de sedação consciente com óxido nitroso é pouco usada pelos cirurgiões-dentistas no Estado do Rio Grande do Sul. É possível que a ampliação do conhecimento acerca da indicação e aplicação do óxido nitroso, ainda durante a graduação, possa expandir o uso e contribuir para uma melhor qualidade no atendimento de pacientes com medo e ansiedade odontológicos. (AU)

Objective: The aim of this study is to evaluate associated factors, perception and prevalence of nitrous oxide use by dental surgeons in Rio Grande do Sul, Brazil. Methodology: A cross-sectional, electronic-based study was carried out with professionals registered in Rio Grande do Sul. Data collection was based on sending, via emails and Instagram campaigns, a questionnaire via the Google Forms platform containing 27 questions about the use of nitrous oxide in dental care, as well as the profile and perceptions of professionals about the technique. Results: Of the 220 participants, only 12.3% used nitrous oxide in their clinical practice, the specialties they used most being surgery and pediatric dentistry. Among those who reported using the technique, 81.5% were over 29 years old (p<0.001) and had a postgraduate course, of which 55.6% completed the qualification course (p<0.01) and more than half (55.6%) reported using it in adult patients (p<0.001). The high cost of the equipment, as well as the lack of interest from professionals, were the main reasons for not using the technique. Conclusion: The conscious sedation technique with nitrous oxide is little used by dental surgeons in the State of Rio Grande do Sul. It is possible that expanding knowledge about the indication and application of nitrous oxide, even during graduation, can expand its use and contribute to a better quality of care for patients with dental fear and anxiety. (AU)

Nitrogen demand and agro-environmental efficiency in Brazilian cereal production / Demanda de nitrogênio e eficiência agro-ambiental na produção brasileira de cereais

This paper aims to analyze the main factors that explain the demand for synthetic nitrogen fertilizers in Brazil, as well as the efficiency of their use. In addition, the research sought to relate the use of fertilizers with nitrous oxide (N2O) emissions. Demand was estimated using the two-stage least squares method (2SLS). Nitrogen use efficiency (NUE) was calculated using an agri-environmental index. The results indicated that demand of nitrogen fertilizers is positively affected by the price of cereal, cereal production and the number of fertilizers used in the past harvest. The calculated NUE presented an average value of 53% in the 1994-2018 period, indicating inefficient use of N. Emissions from nitrogen fertilization grew 59% for the same period. The increasing and / or inadequate rates of fertilizer use have resulted in agro-environmental inefficiency, that is, a decrease in NUE and an increase in N2O emissions. Public policies that guarantee more agricultural technical assistance and rational alternative forms of nitrogen use could contribute to optimizing the synthetic doses applied in production, minimizing adverse environmental effects without generating economic losses to farmers and Brazilian agricultural production.

Este trabalho tem como objetivo analisar os principais fatores que explicam a demanda por fertilizantes nitrogenados sintéticos no Brasil, bem como a eficiência de seu uso. Além disso, a pesquisa buscou relacionar o uso de fertilizantes com as emissões de óxido nitroso (N2O). A demanda foi estimada usando o método dos Mínimos Quadrados em dois Estágios (MQ2E). A eficiência do uso de nitrogênio (EUN) foi calculada por meio de um índice agroambiental. Os resultados indicaram que a demanda de fertilizantes nitrogenados é afetada positivamente pelo preço do cereal, pela produção do cereal e pela quantidade de fertilizantes utilizados na safra passada. A EUN calculada apresentou valor médio de 53% no período 1994-2018, indicando uso ineficiente de N. As emissões da adubação nitrogenada cresceram 59% no mesmo período. Os índices crescentes e/ou inadequados de uso de fertilizantes têm resultado em ineficiência agroambiental, ou seja, diminuição da EUN e aumento das emissões de N2O. Políticas públicas que garantam mais assistência técnica agropecuária e formas alternativas e racionais de uso do nitrogênio poderiam contribuir para otimizar as doses sintéticas aplicadas na produção, minimizando os efeitos ambientais adversos, sem gerar prejuízos econômicos aos agricultores e à produção agrícola brasileira.

Mielopatía cervical secundaria al consumo recreativo de óxido nitroso una afección emergente / Cervical myelopathy secondary to recreational nitrous oxide use: an emergent pathology

Resumen Se describe el caso de una paciente de 27 años que se presentó al servicio de urgencias por hipoestesia y parestesia de dos meses de evolución. El cuadro se inició en ambos pies, progresó en pocos días hasta las rodillas sin trastornos de la marcha y se acompañó de distonías en pulgar e índice de ambas manos. La analítica sanguínea incluyendo tóxicos fue negativa. La resonancia magnética medular mostró una imagen sugestiva de mielopatía o mielitis (C3-C5) sin otras anomalías sugestivas de enfermedad sistémica. El análisis bioquímico y el bacteriológico del líquido cefalorraquídeo fueron normales. Ante estos elementos se re-interrogó a la paciente en busca de consumo de tóxicos inusuales con la confirmación de consumo de óxido nitroso. La paciente fue internada para la realización de otros estudios que confirmaron la hipótesis diagnóstica del servicio de urgencias.

Abstract We describe the case of a 27-year-old female patient who presented to the emergency ward with hypoesthesia and paresthesia developing over the last two months, initially in both feet and progressing to the knees in a few days without associated gait disorders. Dystonia in the thumb and index finger of both hands was noted. Blood tests including toxic drugs were negative. The spinal magnetic resonance imaging was consistent with (C3-C5) myelopathy or myelitis without other abnormalities suggestive of systemic diseases. The biochemi cal and bacteriological analysis of the cerebrospinal fluid was normal. Because of these findings, the patient was re-interviewed to determine the consumption of unusual drugs, and nitrous oxide consumption was referred. The patient was admitted for further studies, which confirmed the diagnosis.

Tratamento cirúrgico de mesiodentes sob sedação consciente com óxido nitroso: relato de caso clínico / Surgical treatment of mesiodens under conscious sedation with nitrous oxide: clinical case report

Dentes supranumerários são caracterizados como um excesso no número de dentes da série normal. Os mesiodentes, definidos pela sua localização mediana aos incisivos centrais superiores, referem-se ao tipo de dente supranumerário mais comumente encontrado na cavidade oral, normalmente intraósseo e assintomático. A presença desses dentes pode ocasionar alterações na dentição permanente, mas a abordagem cirúrgica na fase da dentição mista mostra resultados satisfatórios no alinhamento dental espontâneo. Em pacientes pediátricos, a sedação consciente com óxido nitroso tem demonstrado ser uma alternativa segura e eficaz no controle do medo e da ansiedade. Objetivo: relatar um procedimento cirúrgico de remoção de dois mesiodentes em paciente pediátrico sob anestesia local associada à sedação com óxido nitroso. Relato de caso: paciente do sexo feminino, 11 anos de idade, necessitava de remoção cirúrgica de dois dentes supranumerários localizados em região anterior de maxila. Com a avaliação da tomografia computadorizada, pôde-se observar a posição em que ambos se encontravam. Realizou-se também a exodontia do elemento dentário 14, como solicitado pela ortodontista, para posterior continuidade do tratamento ortodôntico. Devido à complexidade cirúrgica e ao tempo operatório, considerando a idade da paciente e o possível aumento nos níveis de ansiedade, optou-se pela realização de sedação consciente com óxido nitroso. Conclusão: clinicamente, dentes supranumerários podem causar danos locais. O tratamento cirúrgico associado à sedação consciente mostrou-se bastante seguro e efetivo no controle comportamental, além de poder ser implementado na rotina ambulatorial.(AU)

Supernumerary teeth are defined as those in addition to the normal series. The mesiodens, is the most common supernumerary tooth and it is present in the midline between the two central incisors. It is usually intraosseous and asymptomatic. The presence of these teeth may cause changes in permanent dentition and the surgical approach in the mixed dentition phase shows satisfactory results in spontaneous dental alignment. In pediatric patients, conscious sedation with nitrous oxide has been shown to be a safe and effective alternative in controlling fear and anxiety. Objective. To report a surgical procedure for the removal of two mesiodens in a pediatric patient under local anesthesia associated with nitrous oxide sedation. Case report. 11-year-old female patient required surgical removal of two upper mesiodens. The computed tomography images assisted to indicate their exact position. The extraction of the upper right premolar (tooth #14) was also performed as requested by the orthodontist. Considering the patient's age and the possible increase in anxiety levels, along with surgical complexity and operative time, the conscious sedation with nitrous oxide was selected. Conclusion. Clinically, supernumerary teeth cause local damage and surgical treatment associated with conscious sedation has proved to be quite safe and effective in the behavioral control besides being able to be implemented in the outpatient routine.(AU)

Effects of Oral Diazepam or Inhalatory Nitrous OxideOxygen for Conscious Sedation During Third Molar Surgery: A Randomized Controled Trial, Split Mouth Design / Efectos del Diazepam Oral o la Inhalación de Óxido Nitroso-Oxígeno para la Sedación Consciente Durante la Cirugía del Tercer Molar: Un Ensayo Controlado Aleatorio, Diseño de Boca Dividida

ABSTRACT: Anxiety in dental surgery may lead to behavioral and physiological changes for the patient and constitute a frequent challenge for the oral surgeon. The objective of this study was to compare the effect of inhalatory nitrous oxide and oxygen (N2O/O2) with oral diazepam conscious sedation in vital signs of patients undergone third molar extraction. Outpatients who needed removal of partially impacted, bilateral lower third molars, during the period of one year, were included. Each patient underwent conscious sedation with either oral diazepam or inhalatory N2O/O2 on a randomized controlled trial, split-mouth design. Systolic and diastolic blood pressure, heart rate and oxygen blood saturation were the changes measured before, at the beginning and the end of the procedure. Also, surgical procedure duration was recorded. Data from vital signs were submitted to analysis of variance and the duration of the surgery to paired Student's t-test. Twenty-five healthy outpatients (13 women and 12 men) with a mean age of 21.6 years were studied. There was an increase in systolic and diastolic pressure and in heart rate in the beginning; these values decreased and stabilized at the end of the surgical procedure in both treatments (p < 0.001) being lower in N2O/O2 but without difference between treatments. The surgical procedure duration was lower and occurred an expected increase of oximetry under N2O/O2 sedation (p < 0.001). Both treatments were effective for the conscious sedation but N2O/O2 showed better outcomes, mainly in duration of the surgery.

RESUMEN: La ansiedad en la cirugía dentoalveolar puede conducir a alteraciones fisiológicas y de comportamiento en el paciente, constituyendo así un desafío frecuente para el cirujano maxilofacial. El objetivo de este estudio fue comparar el efecto del óxido nitroso inhalatorio con oxígeno (N2O/O2) y la sedación consciente oral con diazepam por médio de los signos vitales de pacientes sometidos a la extracción del tercer molar. Fueron incluídos pacientes ambulatoriales com necesidad de exodoncia de terceros molares inferiores bilaterales, parcialmente impactados, durante el período de un año. Cada paciente fue sometido a sedación consciente con diazepam oral o N2O/O2 por inhalación en un ensayo controlado aleatorio, diseño de boca dividida. La presión arterial sistólica y diastólica, la frecuencia cardíaca y la saturación de oxígeno en la sangre fueron medidos antes, al inicio y al final del procedimiento. Además, se registró la duración del procedimiento quirúrgico. Los datos de los signos vitales fueron enviados para análisis de varianza y la duración de la cirugía para la prueba t de Student pareada. Se estudiaron 25 pacientes ambulatorios sanos (13 mujeres y 12 hombres) con una edad media de 21,6 años. Al início hubo un aumento en la presión sistólica y diastólica y en la frecuencia cardíaca; estos valores disminuyeron y se estabilizaron al final del procedimiento quirúrgico en ambos tratamientos (p <0,001), siendo más bajos en N2O/ O2 pero sin diferencia entre los tratamientos. La duración del procedimiento quirúrgico fue menor y se produjo un aumento esperado de la oximetría bajo sedación con N2O/O2 (p <0,001). Ambos tratamientos fueron efectivos para la sedación consciente, pero el N2O/O2 mostró mejores resultados, principalmente en la duración de la cirugía.

Comparison of endotracheal tube cuff pressure changes using air versus nitrous oxide in anesthetic gases during laparoscopic abdominal surgeries / Comparação de alterações na pressão do balonete do tubo endotraqueal usando ar versus óxido nitroso nos gases anestésicos durante cirurgias abdominais laparoscópicas

Abstract Background and objectives The purpose of this study was to compare the endotracheal tube cuff pressure changes during laparoscopic surgeries using air versus nitrous-oxide in anesthetic gas mixture; and to observe the incidences of postoperative sore throat, hoarseness and dysphagia. Methods Total 100 patients scheduled for elective laparoscopic abdominal surgery were allocated into two groups. Group A (n = 50) received air while Group N (n = 50) received nitrous-oxide in anesthetic gas mixture. After endotracheal intubation, cuff was inflated with air to achieve sealing pressure. Cuff pressure at baseline (sealing pressure), 30 min, 60 min and 90 min was recorded with a manometer. Incidence of sore throat, hoarseness and dysphagia was noted at the time of discharge from post-anesthesia care unit and 24 h after extubation. Results Cuff pressure increased from baseline in both the groups. The increase in cuff pressure in Group N was greater than that in Group A at all time points studied (p < 0.001). Within Group A, cuff pressure increased more at 90 min than at 30 min (p < 0.05). Within Group N, increase in cuff pressure was more at each time point (30, 60 and 90 min) than its previous time point (p < 0.05). The incidence of sore throat in post-anesthesia care unit was higher in Group N than in Group A. Conclusion Use of nitrous-oxide during laparoscopy increases cuff pressure resulting in increased incidence of postoperative sore throat. Cuff pressure should be monitored routinely during laparoscopy with nitrous-oxide anesthesia.

Resumo Justificativa e objetivos O objetivo deste estudo foi comparar as alterações na pressão do balonete do tubo endotraqueal durante cirurgias laparoscópicas usando ar versus óxido nitroso na mistura dos gases anestésicos e observar a incidência de dor de garganta, rouquidão e disfagia no pós-operatório. Métodos No total, 100 pacientes agendados para cirurgia abdominal laparoscópica eletiva foram alocados em dois grupos: Grupo A (n = 50) recebeu ar e Grupo N (n = 50) recebeu óxido nitroso na mistura de gases anestésicos. Após a intubação endotraqueal, o balonete foi insuflado com ar para obter a pressão de vedação. As pressões do balonete na fase basal (pressão de vedação), aos 30 min, 60 min e 90 min foram registradas com um manômetro. A incidência de dor de garganta, rouquidão e disfagia foi observada no momento da alta da sala de recuperação pós-anestésica e 24 horas após a extubacão. Resultados A pressão do balonete aumentou em ambos os grupos, comparada à pressão basal. O aumento da pressão do balonete foi maior no Grupo N do que no Grupo A em todos os tempos avaliados (p < 0,001). No Grupo A, o aumento da pressão do balonete foi maior aos 90 min do que aos 30 min (p < 0,05). No Grupo N, o aumento da pressão do balonete foi maior em cada um dos tempos (30, 60 e 90 min) do que no tempo anteriormente mensurado (p < 0,05). A incidência de dor de garganta na sala de recuperação pós-anestésica foi maior no Grupo N do que no Grupo A. Conclusão O uso de óxido nitroso durante a laparoscopia aumenta a pressão do balonete, resulta em aumento na incidência de dor da garganta no pós-operatório. A pressão do balonete deve ser rotineiramente monitorada durante a laparoscopia sob anestesia com óxido nitroso.

[Comparison of endotracheal tube cuff pressure changes using air versus nitrous oxide in anesthetic gases during laparoscopic abdominal surgeries]. / Comparação de alterações na pressão do balonete do tubo endotraqueal usando ar versus óxido nitroso nos gases anestésicos durante cirurgias abdominais laparoscópicas.

BACKGROUND AND OBJECTIVES: The purpose of this study was to compare the endotracheal tube cuff pressure changes during laparoscopic surgeries using air versus nitrous-oxide in anesthetic gas mixture; and to observe the incidences of postoperative sore throat, hoarseness and dysphagia. METHODS: Total 100 patients scheduled for elective laparoscopic abdominal surgery were allocated into two groups. Group A (n=50) received air while Group N (n=50) received nitrous-oxide in anesthetic gas mixture. After endotracheal intubation, cuff was inflated with air to achieve sealing pressure. Cuff pressure at baseline (sealing pressure), 30min, 60min and 90min was recorded with a manometer. Incidence of sore throat, hoarseness and dysphagia was noted at the time of discharge from post-anesthesia care unit and 24h after extubation. RESULTS: Cuff pressure increased from baseline in both the groups. The increase in cuff pressure in Group N was greater than that in Group A at all time points studied (p<0.001). Within Group A, cuff pressure increased more at 90min than at 30min (p<0.05). Within Group N, increase in cuff pressure was more at each time point (30, 60 and 90min) than its previous time point (p<0.05). The incidence of sore throat in post-anesthesia care unit was higher in Group N than in Group A. CONCLUSION: Use of nitrous-oxide during laparoscopy increases cuff pressure resulting in increased incidence of postoperative sore throat. Cuff pressure should be monitored routinely during laparoscopy with nitrous-oxide anesthesia.

Eficácia e segurança da sedação consciente com óxido nitroso no tratamento pediátrico odontológico: uma revisão de estudos clínicos / Effectiveness and safety of nitrous oxide in pediatric dentistry: a review of clinical studies

Objetivo: analisar a utilização da sedação consciente com óxido nitroso/oxigênio, sua eficácia e segurança durante o tratamento pediátrico. Métodos: foi realizada busca nas bases de dados do Pubmed/Medline e manual nas principais revistas da área. Todavia, não avaliando somente eficácia e segurança, mas também, comparando a sedação com óxido nitroso com demais técnicas tradicionais, sendo usada como complemento de técnicas ou analisando diferenças na aplicação do óxido nitroso. Resultados: os estudos demonstraram que a sedação consciente foi eficaz no tratamento odontopediátrico e segura quando realizada por profissionais treinados para exercer esta aplicação em determinados pacientes, sendo estes corretamente avaliados quanto a estarem aptos a receber a sedação. Nos demais resultados, foi obtido bom atendimento, com diminuição do choro e estado de alerta da criança, ao combinar, por exemplo, manejo comportamental com óxido nitroso, o medo diminuiu ainda mais, entretanto, não foi apresentado efeitos analgésicos na maioria dos casos e não houve diminuição no tempo de consulta com o uso do óxido nitroso, embora, também não requereu maior número de seções. Conclusão: A sedação consciente com oxido nitroso foi uma técnica segura e eficaz para utilização em crianças, desde que o profissional seja habilitado e a criança apta para passar pelo processo de sedação inalatória(AU)

Objective: to analyze the use of conscious sedation with nitrous oxide / oxygen, its efficacy and safety during pediatric treatment. Methods: we searched the Pubmed/Medline databases and searched the main journals in the area. However, not only evaluating efficacy and safety, but also comparing sedation with nitrous oxide with other traditional techniques, being used as a complement to techniques or analyzing differences in the application of nitrous oxide. Results: the studies demonstrated that conscious sedation was effective in pediatric dentistry and safe when performed by professionals trained to exercise this application in certain patients, being correctly evaluated in terms of being able to receive sedation. In the other results, good care was obtained, with decreased crying and alertness of the child, by combining, for example, behavioral management with nitrous oxide, fear decreased even more, however, no analgesic effects were present in most cases and there was no decrease in the time of consultation with the use of nitrous oxide, although it did not require a greater number of sections. Conclusion: Conscious sedation with nitrous oxide was a safe and effective technique for use in children, provided that the professional is qualified and the child is able to undergo the process of inhalation sedation(AU)

Emisión de óxido nitroso, nitrificación, desnitrificación y mineralización de nitrógeno durante el cultivo del arroz en 2 suelos de Uruguay / Nitrous oxide emission, nitrification, denitrification and nitrogen mineralization during rice growing season in 2 soils from Uruguay

Los procesos microbianos como la mineralización, la nitrificación y la desnitrificación regulan la dinámica del nitrógeno en el suelo. Estos 2 últimos son los principales responsables de la emisión de óxido nitroso (N2O). En este trabajo se determinaron los flujos de N2O en momentos clave del ciclo de cultivo del arroz en 2 sitios que diferían principalmente en el contenido de materia orgánica del suelo (MO), en las localidades de Salto (mayor MO) y de Treinta y Tres. Dichos momentos clave fueron a la siembra, en macollaje, en primordio floral y a la madurez. También se determinó el potencial de mineralización neta de N y las actividades y los números más probables (NMP) de oxidantes de NH4+ y de desnitrificantes. El potencial de mineralización de N, así como la actividad y el NMP de oxidantes de NH4+, no variaron con el tipo de suelo. Sin embargo, la actividad y el NMP de desnitrificantes fueron mayores en el suelo con mayor contenido de MO, independiente de la etapa del cultivo. A su vez, en las etapas finales del ciclo del cultivo, el NMP de desnitrificantes aumentó coincidiendo con el mayor potencial de mineralización y el mayor contenido de N mineral del suelo. Solo se observó un incremento en el flujo de N2O en el suelo de Salto a la madurez del arroz y cuando el suelo ya había sido drenado (44,2g N-N2O/ha d, frente a 20,8g N-N2O/ha d en Treinta y Tres). Esta investigación señala la importancia de estudiar las emisiones en distintos tipos de suelos y de continuar la medición luego del drenaje del cultivo de arroz para la elaboración de los inventarios de gases de efecto invernadero.

Microbial processes such as mineralization, nitrification and denitrification regulate nitrogen dynamics in the soil. The last two processes may produce nitrous oxide (N2O). In this work N2O fluxes were quantified at four moments of the rice cycle, sowing, tillering, panicle initiation and maturity, in two sites that differed mainly in their soil organic matter (OM) content, Salto (higher OM) and Treinta y Tres. Potential net N mineralization, ammonium oxidation and denitrification as well as the most probable numbers (MPN) of ammonia oxidizers and denitrifiers were determined. Potential N mineralization did not vary with the soil type and increased at rice maturity. Neither ammonia oxidation potential nor MPN were different among the soils. However, the soil with higher OM exhibited higher activity and MPN of denitrifiers, irrespective of the rice stage. In turn, at the latest phases of the crop, the MPN of denitrifiers increased coinciding with the highest mineralization potential and mineral N content of the soil. Significant differences in N2O flux were observed in Salto, where the highest emissions were detected at rice maturity, after the soil was drained (44.2 vs 20.8g N-N2O/ha d in Treinta y Tres). This work shows the importance of considering the soil type and end-of-season drainage of the rice field to elaborate GHGs (greenhouse gases) inventories.

[Nitrous oxide emission, nitrification, denitrification and nitrogen mineralization during rice growing season in 2 soils from Uruguay]. / Emisión de óxido nitroso, nitrificación, desnitrificación y mineralización de nitrógeno durante el cultivo del arroz en 2 suelos de Uruguay.

Microbial processes such as mineralization, nitrification and denitrification regulate nitrogen dynamics in the soil. The last two processes may produce nitrous oxide (N2O). In this work N2O fluxes were quantified at four moments of the rice cycle, sowing, tillering, panicle initiation and maturity, in two sites that differed mainly in their soil organic matter (OM) content, Salto (higher OM) and Treinta y Tres. Potential net N mineralization, ammonium oxidation and denitrification as well as the most probable numbers (MPN) of ammonia oxidizers and denitrifiers were determined. Potential N mineralization did not vary with the soil type and increased at rice maturity. Neither ammonia oxidation potential nor MPN were different among the soils. However, the soil with higher OM exhibited higher activity and MPN of denitrifiers, irrespective of the rice stage. In turn, at the latest phases of the crop, the MPN of denitrifiers increased coinciding with the highest mineralization potential and mineral N content of the soil. Significant differences in N2O flux were observed in Salto, where the highest emissions were detected at rice maturity, after the soil was drained (44.2 vs 20.8g N-N2O/ha d in Treinta y Tres). This work shows the importance of considering the soil type and end-of-season drainage of the rice field to elaborate GHGs (greenhouse gases) inventories.

Evaluación de signos vitales, conducta y nivel de sedación en pacientes no cooperadores bajo sedación consciente con óxido nitroso

Objetivo: El propósito fue evaluar la efectividad de la sedación inhalada con óxido nitroso en la conducta, variación de signos vitales, el nivel de sedación y la molestia durante el tratamiento odontológico de niños no cooperadores. Metodología: La muestra fue de 26 niños de ambos sexos de 3 a 6 años, con una media de 4,6 años, que cumplieron con criterios de selección; conducta no cooperadora según la escala de Frankl, ASA I, ayuno preoperatorio, y cuyos padres hayan consentido que sus hijos participen en el estudio. La administración del óxido nitroso se realizó, considerando las directrices de sedación de la Academia Americana de Odontología Pediátrica, Los tratamientos fueron operatoria dental en lesiones de caries con grado 4 y 5 según el Sistema Internacional para la Detección y Evaluación de Caries. Resultados: La conducta negativa mejora significativamente con la aplicación del óxido nitroso a un nivel de significancia del 5%. Los signos vitales durante el tratamiento dental con óxido nitroso variaron dentro de los parámetros normales y no se evidenciaron efectos secundarios. Conclusiones: La sedación inhalada con óxido nitroso es efectiva y segura para pacientes no cooperadores durante el tratamiento dental.

Air pollution and risk of hospitalization for epilepsy: the role of farm use of nitrogen fertilizers and emissions of the agricultural air pollutant, nitrous oxide / Poluição do ar e risco de hospitalização por epilepsia: o papel do uso agrícola de fertilizantes nitrogenados e as emissões de poluente atmosférico agrícola, óxido nitroso

ABSTRACT The link between various air pollutants and hospitalization for epilepsy has come under scrutiny. We have proposed that exposure to air pollution and specifically the pervasive agricultural air pollutant and greenhouse gas, nitrous oxide (N2O), may provoke susceptibility to neurodevelopmental disorders. Evidence supports a role of N2O exposure in reducing epileptiform seizure activity, while withdrawal from the drug has been shown to induce seizure-like activity. Therefore, we show here that the statewide use of anthropogenic nitrogen fertilizers (the most recognized causal contributor to environmental N2O burden) is significantly negatively associated with hospitalization for epilepsy in all three pre-specified hospitalization categories, even after multiple pollutant comparison correction (p<.007), while the other identified pollutants were not consistently statistically significantly associated with hospitalization for epilepsy. We discuss potential neurological mechanisms underpinning this association between air pollutants associated with farm use of anthropogenic nitrogen fertilizers and hospitalization for epilepsy.

RESUMO A ligação entre vários poluentes do ar e a hospitalização por epilepsia tem sido examinada. Propusemos que a exposição à poluição do ar, especificamente ao poluente atmosférico generalizado e ao gás de efeito estufa, o óxido nitroso (N2O), poderiam fomentar a susceptibilidade a distúrbios do desenvolvimento neurológico. A evidência apoia o papel da exposição ao N2O na redução da atividade convulsiva epileptiforme, enquanto mostra que a retirada do fármaco induz atividade pseudo-convulsiva. Portanto, mostramos aqui que o uso a nível estatal de fertilizantes nitrogenados antropogênicos (o agente causal mais reconhecido para a carga ambiental de N2O) está significativa e negativamente associado à hospitalização por epilepsia nas três categorias de hospitalização pré-especificadas, mesmo após a correção de comparação de poluentes múltiplos (p <0,007 ), enquanto os outros poluentes identificados não foram consistentemente associados de forma estatística com a hospitalização por epilepsia. Discutimos possíveis mecanismos neurológicos subjacentes a esta associação entre poluentes atmosféricos associados ao uso agrícola de fertilizantes nitrogenados antropogênicos, e hospitalização por epilepsia.

Effect of nitrous oxide on fentanyl consumption in burned patients undergoing dressing change / Efeito do óxido nitroso sobre o consumo de fentanil em pacientes queimados submetidos à troca de curativo

BACKGROUND AND OBJECTIVES: Thermal injuries and injured areas management are important causes of pain in burned patients, requiring that these patients are constantly undergoing general anesthesia for dressing change. Nitrous oxide (N2O) has analgesic and sedative properties; it is easy to use and widely available. Thus, the aim of this study was to evaluate the analgesic effect of N2O combined with fentanyl in burned patients during dressing change. METHOD: After approval by the institutional Ethics Committee, 15 adult burned patients requiring daily dressing change were evaluated. Patient analgesia was controlled with fentanyl 0.0005% administered by intravenous pump infusion on-demand. Randomly, in one of the days a mixture of 65% N2O in oxygen (O2) was associated via mask, with a flow of 10 L/min (N2O group) and on the other day only O2 under the same flow (control group). RESULTS: No significant pain reduction was seen in N2O group compared to control group. VAS score before dressing change was 4.07 and 3.4, respectively, in N2O and control groups. Regarding pain at the end of the dressing, patients in N2O group reported pain severity of 2.8; while the control group reported 2.87. There was no significant difference in fentanyl consumption in both groups. CONCLUSIONS: The association of N2O was not effective in reducing opioid consumption during dressing changes.

JUSTIFICATIVA E OBJETIVOS: Os ferimentos térmicos e a manipulação das áreas lesadas são causas importantes de dor em pacientes vítimas de queimaduras, necessitando que estes pacientes sejam constantemente submetidos a anestesias gerais para a troca do curativo. O óxido nitroso (N2O) tem propriedades analgésicas e sedativas, sendo capaz de fácil utilização e de ampla disponibilidade. Com isto, objetivou-se avaliar o efeito analgésico da administração de N2O associado ao fentanil em pacientes queimados, durante a troca de curativo. MÉTODO: Após aprovação pela comissão de ética institucional, foram avaliados 15 pacientes adultos, vítimas de queimaduras com necessidade de troca diária de curativo. A analgesia do paciente foi controlada pelo uso de fentanil 0,0005% administrado por bomba de infusão sob demanda, intravenosa. De maneira aleatória, em um dos dias foi associada mistura de N2O a 65% em oxigênio (O2) sob máscara com fluxo de 10 L/min (grupo N2O) e no outro dia apenas O2 sob o mesmo fluxo (grupo controle). RESULTADOS: Não se observou diminuição significativa da dor no grupo N2O em relação ao grupo controle. A dor na EAV antes da troca do curativo foi de 4,07 e 3,4; respectivamente nos grupos N2O e controle. Quanto à dor ao término da troca de curativo, os pacientes do grupo N2O referiram dor intensidade 2,8; enquanto no grupo controle foi de 2,87. Não houve diferença significativa de consumo de fentanil em ambos os grupos. CONCLUSÕES: A associação de N2O não foi eficaz na redução no consumo de opióides durante a troca de curativos.

Effect of nitrous oxide on fentanyl consumption in burned patients undergoing dressing change.

BACKGROUND AND OBJECTIVES: Thermal injuries and injured areas management are important causes of pain in burned patients, requiring that these patients are constantly undergoing general anesthesia for dressing change. Nitrous oxide (N2O) has analgesic and sedative properties; it is easy to use and widely available. Thus, the aim of this study was to evaluate the analgesic effect of N2O combined with fentanyl in burned patients during dressing change. METHOD: After approval by the institutional Ethics Committee, 15 adult burned patients requiring daily dressing change were evaluated. Patient analgesia was controlled with fentanyl 0.0005% administered by intravenous pump infusion on-demand. Randomly, in one of the days a mixture of 65% N2O in oxygen (O2) was associated via mask, with a flow of 10 L/min (N2O group) and on the other day only O2 under the same flow (control group). RESULTS: No significant pain reduction was seen in N2O group compared to control group. VAS score before dressing change was 4.07 and 3.4, respectively, in N2O and control groups. Regarding pain at the end of the dressing, patients in N2O group reported pain severity of 2.8; while the control group reported 2.87. There was no significant difference in fentanyl consumption in both groups. CONCLUSIONS: The association of N2O was not effective in reducing opioid consumption during dressing changes.

[Effect of nitrous oxide on fentanyl consumption in burned patients undergoing dressing change]. / Efeito do óxido nitroso sobre o consumo de fentanil em pacientes queimados submetidos à troca de curativo.

BACKGROUND AND OBJECTIVES: Thermal injuries and injured areas management are important causes of pain in burned patients, requiring that these patients are constantly undergoing general anesthesia for dressing change. Nitrous oxide (N2O) has analgesic and sedative properties; it is easy to use and widely available. Thus, the aim of this study was to evaluate the analgesic effect of N2O combined with fentanyl in burned patients during dressing change. METHOD: After approval by the institutional Ethics Committee, 15 adult burned patients requiring daily dressing change were evaluated. Patient analgesia was controlled with fentanyl 0.0005% administered by intravenous pump infusion on-demand. Randomly, in one of the days a mixture of 65% N2O in oxygen (O2) was associated via mask, with a flow of 10 L/min (N2O group) and on the other day only O2 under the same flow (control group). RESULTS: No significant pain reduction was seen in N2O group compared to control group. VAS score before dressing change was 4.07 and 3.4, respectively, in N2O and control groups. Regarding pain at the end of the dressing, patients in N2O group reported pain severity of 2.8; while the control group reported 2.87. There was no significant difference in fentanyl consumption in both groups. CONCLUSIONS: The association of N2O was not effective in reducing opioid consumption during dressing changes.

Impact of hydroquinone used as a redox effector model on potential denitrification, microbial activity and redox condition of a cultivable soil.

In this microcosm study, we analyzed the effect produced by hydroquinone on the expression of soil biological denitrification, in relation to the redox state of the soil, both in terms of intensity factor (Eh') and capacity factor (amount of oxidized or reduced compounds). The supplementation of an Argiudoll soil with hydroquinone decreased the soil apparent reduction potential (Eh') and soil dehydrogenase activity (formazan production from tetrazolium chloride reduction; redox capacity factor), the relationship between both factors being highly significative, r=0.99 (p<0.001). The bacterial population (measured by colony forming units) increased, and the production of N2O was greater (p<0.001) at 200 and 400µg/g dry soil doses. Furthermore, there was an inverse relationship between soil dehydrogenase activity and the number of bacteria (r=-0.82; p<0.05), increased denitrification activity and changes in the CO2/N2O ratio value. These results suggest that hydroquinone at supplemented doses modified the soil redox state and the functional structure of the microbial population. Acetate supplementation on soil with hydroquinone, to ensure the availability of an energy source for microbial development, confirmed the tendency of the results obtained with the supplementation of hydroquinone alone. The differences observed at increased doses of hydroquinone might be explained by differences on the hydroquinone redox species between treatments.

El impacto de la hidroquinona usada como un modelo de efector redox sobre la desnitrificación potencial, la actividad microbiana y las condiciones redox de un suelo cultivable / Impact of hydroquinone used as a redox effector model on potential denitrification, microbial activity and redox condition of a cultivable soil

In this microcosm study, we analyzed the effect produced by hydroquinone on the expression of soil biological denitrification, in relation to the redox state of the soil, both in terms of intensity factor (Eh′) and capacity factor (amount of oxidized or reduced compounds). The supplementation of an Argiudoll soil with hydroquinone decreased the soil apparent reduction potential (Eh′) and soil dehydrogenase activity (formazan production from tetrazolium chloride reduction; redox capacity factor), the relationship between both factors being highly significative, r = 0.99 (p < 0.001). The bacterial population (measured by colony forming units) increased, and the production of N2O was greater (p < 0.001) at 200 and 400 μg/g dry soil doses. Furthermore, there was an inverse relationship between soil dehydrogenase activity and the number of bacteria (r = −0.82; p < 0.05), increased denitrification activity and changes in the CO2/N2O ratio value. These results suggest that hydroquinone at supplemented doses modified the soil redox state and the functional structure of the microbial population. Acetate supplementation on soil with hydroquinone, to ensure the availability of an energy source for microbial development, confirmed the tendency of the results obtained with the supplementation of hydroquinone alone. The differences observed at increased doses of hydroquinone might be explained by differences on the hydroquinone redox species between treatments.

En este trabajo estudiamos, en condiciones de microcosmos, el efecto que produce la hidroquinona sobre la expresión de la desnitrificación en relación con el estado de óxido-reducción del suelo, en términos de factor de intensidad (Eh′) y de factor de capacidad (cantidad de compuestos oxidados o reducidos). La suplementación de un suelo argiudol con hidroquinona disminuyó el potencial de reducción aparente (Eh′) y la actividad deshidrogenasa (producción de formazán a partir de la reducción de cloruro de tetrazolio; factor de capacidad redox), la relación entre ambos factores fue altamente significativa, r = 0,99 (p < 0,001). La población bacteriana heterotrófica (medida como unidades formadoras de colonias) aumentó y la producción de N2O fue mayor (p < 0,001) con las dosis de 200 y 400 μg/g de suelo seco. Además se observó una relación inversa entre la producción de formazán y el número de bacterias (r = −0,82; p < 0,05), la actividad desnitrificadora aumentó y se produjeron cambios en el valor del cociente CO2/N2O. Estos resultados sugieren que la hidroquinona, en las dosis empleadas, modificó el estado redox del suelo y la estructura funcional de la población microbiana. La suplementación con acetato en el suelo con hidroquinona, a fin de asegurar la disponibilidad de una fuente de energía para el desarrollo bacteriano, confirmó la tendencia de los resultados obtenidos con la suplementación con hidroquinona solamente. Las diferencias observadas con el incremento en la dosis de hidroquinona podrían explicarse por las diferencias sobre las especies redox de la hidroquinona entre los tratamientos.

Chronic pain relief after the exposure of nitrous oxide during dental treatment: longitudinal retrospective study / Alívio da dor crônica após exposição ao óxido nitroso durante tratamento odontológico: estudo retrospectivo longitudinal

The objective was to investigate the effect of nitrous/oxygen in chronic pain. Seventy-seven chronic pain patients referred to dental treatment with conscious sedation with nitrous oxide/oxygen had their records included in this research. Data were collected regarding the location and intensity of pain by the visual analogue scale before and after the treatment. Statistical analysis was performed comparing pre- and post-treatment findings. It was observed a remarkable decrease in the prevalence of pain in this sample (only 18 patients still had chronic pain, p < 0.001) and in its intensity (p < 0.001). Patients that needed fewer sessions received higher proportions of nitrous oxide/oxygen. Nitrous oxide may be a tool to be used in the treatment of chronic pain, and future prospective studies are necessary to understand the underlying mechanisms and the effect of nitrous oxide/oxygen in patients according to the pain diagnosis and other characteristics.

O objetivo deste estudo foi investigar o efeito do óxido nitroso na dor crônica. Os prontuários de 77 pacientes com dor crônica submetidos a tratamento odontológico com sedação consciente (óxido nitroso/oxigênio) foram incluídos. Os dados sobre localização e intensidade de dor pela escala visual analógica foram considerados, e foi realizada comparação e análise estatística entre os momentos pré- e pós-tratamento. Foi observada redução marcante na prevalência de dor nesta amostra (apenas 18 doentes ainda tinham dor, p < 0,001) e na intensidade de dor (p < 0,001). Os doentes que precisaram de menor quantidade de sessões receberam maiores proporções de óxido nitroso/oxigênio. Em conclusão, pode-se considerar o oxido nitroso como uma ferramenta a ser investigada no tratamento da dor crônica em estudos futuros prospectivos, que poderão identificar os mecanismos associados de acordo com o diagnóstico de dor e outras características.