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.

Forage peanut legume as a strategy for improving beef production without increasing livestock greenhouse gas emissions.

The transformation of pastures from a degraded state to sustainable productivity is a major challenge in tropical livestock production. Stoloniferous forage legumes such as Arachis pintoi (forage peanut) are one of the most promising alternatives for intensifying pasture-based beef livestock operations with reduced greenhouse gas (GHG) emissions. This 2-year study assessed beef cattle performance, nutrient intake and digestibility, and balance of GHG emissions in three pasture types (PT): (1) mixed Palisade grass - Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster (syn. Brachiaria brizantha Stapf cv. Marandu) and forage peanut (A. pintoi Krapov. & W.C. Greg. cv. BRS Mandobi) pastures (Mixed), (2) monoculture Palisade grass pastures with 150 kg of N/ha per year (Fertilised), and (3) monoculture Palisade grass without N fertiliser (Control). Continuous stocking with a variable stocking rate was used in a randomised complete block design, with four replicates per treatment. The average daily gain and carcass gain were not influenced by the PT (P = 0.439 and P = 0.100, respectively) and were, on average, 0.433 kg/animal per day and 83.4 kg/animal, respectively. Fertilised and Mixed pastures increased by 102 and 31.5%, respectively, the liveweight gain per area (kg/ha/yr) compared to the Control pasture (P < 0.001). The heifers in the Mixed pasture had lower CH4 emissions (g/animal per day; P = 0.009), achieving a reduction of 12.6 and 10.1% when compared to the Fertilised and Control pastures, respectively. Annual (N2O) emissions (g/animal) and per kg carcass weight gain were 59.8 and 63.1% lower, respectively, in the Mixed pasture compared to the Fertilised pasture (P < 0.001). Mixed pasture mitigated approximately 23% of kg CO2eq/kg of carcass when substituting 150 kg of N/ha per year via fertiliser. Mixed pastures with forage peanut are a promising solution to recover degraded tropical pastures by providing increased animal production with lower GHG emissions.

Greenhouse gases capture applying impregnated silica with ionic liquids, deep eutectic solvents, and natural deep eutectic solvents.

The development of technologies to capture greenhouse gases (GHGs) like carbon dioxide (CO2) and nitrous oxide (N2O) is vital for climate change mitigation. Ionic liquids (ILs), deep eutectic solvents (DES), and natural deep eutectic solvents (NADES) are promising absorbents to abate GHGs emissions. However, their high viscosity limits the gas-liquid contact, as consequence of the mass transfer. To overcome this, their impregnation onto porous silica gel has been carried out, increasing the gas-liquid contact area. The present study analyzes the effect of size particle of silica gel impregnated with ILs, DES, and NADES over the CO2 and N2O capture at atmospheric conditions. The degree of impregnation of silica particles was determined by thermogravimetric analysis (TGA). The identification of functional groups present on the surface of silica, ILs, DES, and NADES was performed using Fourier-transform infrared spectroscopy (FTIR), and their crystalline structure was determined by X-ray diffraction (XRD). The partition coefficient of CO2 and N2O between gas and ILs, DES, and NADES was determined by a static headspace method. Results show that the degree of solvent impregnation on silica gel ranged from 36.8 to 43.0% w/w, the partition coefficient of CO2 in the impregnated silica varied from 0.005 to 0.067, and for N2O, from 0.005 to 0.032. This suggests that impregnated particles have a greater affinity for N2O compared to CO2. Using impregnated particles requires only 40% of the bulk solvent to achieve a similar GHG capture capacity compared to using bulk solvents.

Comparison of Efficacy and Safety of Midazolam versus Nitrous Oxide as Sedative Agents during Paediatric Dental Treatment: A Systematic Review / Comparison of Efficacy and Safety of Midazolam versus Nitrous Oxide as Sedative Agents during Paediatric Dental Treatment: A Systematic Review

ABSTRACT Objective: To identify and study the existing literature on the efficacy and safety of midazolam compared to inhalation of nitrous oxide in children undergoing dental treatment. Material and Methods: Electronic resources such as PubMed Central, Cochrane Database of Systematic Reviews, Lilacs, Science Direct, and SIGLE were thoroughly searched. The title scan was used to find randomised controlled trials reviewed for inclusion by reading the abstract. Studies comparing the sedative, behavioural, and anxiolytic effects and safety in children undergoing dental treatment under midazolam and nitrous oxide inhalation were included. The Cochrane Reviews system software, Revman 5.4.1, was used to assess the quality of the included studies. Results: 11328 articles were identified by screening the electronic databases, of which 10906 were eliminated after titles were read and duplicates were removed. Ten full-text articles were examined, of which three were excluded as they did not match the eligibility criteria. Hence, a total of 7 studies were included. Midazolam and nitrous oxide inhalation were not statistically different in terms of the success of treatment and behaviour modification. However, midazolam showed a deeper level of sedation and resulted in amnesia in more children when compared to nitrous oxide sedation. All of the included studies were found to have a high risk of bias. Conclusion: Though all the studies included showed an increased risk of bias, midazolam and nitrous oxide inhalation seem equally effective sedative agents for controlling behaviour in children undergoing dental treatment. Midazolam shows a deeper sedation level when given orally and produces a higher rate of anterograde amnesia.

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.

Greenhouse gas balance and mitigation of pasture-based dairy production systems in the Brazilian Atlantic Forest Biome.

Brazilian cattle production is mostly carried out in pastures, and the need to mitigate the livestock's greenhouse gas (GHG) emissions and its environmental footprint has become an important requirement. The adoption of well-suited breeds and the intensification of pasture-based livestock production systems are alternatives to optimize the sector's land use. However, further research on tropical systems is necessary. The objective of this research was to evaluate the effect of Holstein (HO) and Jersey-Holstein (JE x HO) crossbred cows in different levels of pasture intensification (continuous grazing system with low stocking rate-CLS; irrigated rotational grazing system with high stocking rate-RHS), and the interaction between these two factors on GHG mitigation. Twenty-four HO and 24 JE x HO crossbred dairy cows were used to evaluate the effect of two grazing systems on milk production and composition, soil GHG emissions, methane (CH4) emission, and soil carbon accumulation (0-100 cm). These variables were used to calculate carbon balance (CB), GHG emission intensity, the number of trees required to mitigate GHG emission, and the land-saving effect. The number of trees necessary to mitigate GHG emission was calculated, considering the C balance within the farm gate. The mitigation of GHG emissions comes from the annual growth rate and accumulation of C in eucalyptus trees' trunks. The CB of all systems and genotypes presented a deficit in carbon (C); there was no difference for genotypes, but RHS was more deficient than CLS (-4.99 to CLS and -28.72 to RHS ton CO2e..ha-1.year-1). The deficit of C on GHG emission intensity was similar between genotypes and higher for RHS (-0.480 to RHS and -0.299 to CLS kg CO2e..kg FCPCmilk-1). Lower GHG removals (0.14 to CLS higher than 0.02 to RHS kg CO2e..kg FCPCmilk-1) had the greatest influence on the GHG emission intensity of milk production. The deficit number of trees to abatement emissions was higher to HO (-46.06 to HO and -38.37 trees/cow to JE x HO) and to RHS (-51.9 to RHS and -33.05 trees/cow to CLS). However, when the results are expressed per ton of FCPCmilk, there was a difference only between pasture management, requiring -6.34 tree. ton FCPCmilk-1 for the RHS and -3.99 tree. ton FCPCmilk-1 for the CLS system. The intensification of pastures resulted in higher milk production and land-saving effect of 2.7 ha. Due to the reservation of the pasture-based dairy systems in increasing soil C sequestration to offset the GHG emissions, especially enteric CH4, planting trees can be used as a mitigation strategy. Also, the land-save effect of intensification can contribute to the issue, since the area spared through the intensification in pasture management becomes available for reforestation with commercial trees.

Is Dairy Effluent an Alternative for Maize Crop Fertigation in Semiarid Regions? An Approach to Agronomic and Environmental Effects.

The reuse of effluents from intensive dairy farms combined with localized irrigation techniques (fertigation) has become a promising alternative to increase crop productivity while reducing the environmental impact of waste accumulation and industrial fertilizers production. Currently, the reuse of dairy effluents through fertigation by subsurface drip irrigation (SDI) systems is of vital importance for arid regions but it has been poorly studied. The present study aimed to assess the greenhouse gas (GHG) emissions, soil properties, and crop yield of a maize crop fertigated with either treated dairy effluent or dissolved granulated urea applied through an SDI system at a normalized N application rate of 200 kg N ha-1. Fertilizer application was divided into six fertigation events. GHG fluxes were measured during fertigation (62-day) using static chambers. Soil properties were measured previous to fertilizer applications and at the harvest coinciding with crop yield estimation. A slight increase in soil organic matter was observed in both treatments for the 20-60 cm soil depth. Both treatments also showed similar maize yields, but the dairy effluent increased net GHG emissions more than urea during the fertigation period. Nevertheless, the net GHG emissions from the dairy effluent were lower than the theoretical CO2eq emission that would have been emitted during urea manufacturing or the longer storage of the effluent if it had not been used, showing the need for life-cycle assessments. Local-specific emission factors for N2O were determined (0.07%), which were substantially lower than the default value (0.5%) of IPCC 2019. Thus, the subsurface drip irrigation systems can lead to low GHG emissions, although further studies are needed.

Effects of condensed tannins on greenhouse gas emissions and nitrogen dynamics from urine-treated grassland soil.

Condensed tannins are a potentially important treatment option to mitigate N2O (nitrous oxide) and affect carbon dioxide (CO2) and methane (CH4) emissions; however, their effect has been poorly assessed. Here, we quantified the emissions of N2O, CH4, and CO2, soil N mineralization, and nitrification with increasing doses of condensed tannins added to the urine of cattle raised on pasture. The experiment consisted of incubation with doses of 0%, 0.5%, and 1.0% of condensed tannins added directly to the collected urine. The experimental design was completely randomized. Greenhouse gas fluxes were quantified for four weeks using static chambers and gas chromatography. The addition of condensed tannins increased N2O emissions (P < 0.05), with total emissions averaging 95.84 mg N-N2O kg-1, 265.30 mg N-N2O kg-1, and 199.32 mg N-N2O kg-1 dry soil in the treatments with 0%, 0.5%, and 1% tannins, respectively. Methane emissions were reduced with the addition of tannins (P < 0.05), with total emissions of 8.84 g CH4 kg-1, 1.87 g CH4 kg-1, and 3.34 g CH4 kg-1 dry soil in the treatments with 0%, 0.5%, and 1% tannins, respectively. Soil respiration increased with the addition of condensed tannins (P < 0.05), with total emissions of 3.80 g CO2 kg-1, 6.93 g CO2 kg-1, and 5.87 g CO2 kg-1 in dry soil, in the treatments with 0%, 0.5%, and 1% tannins, respectively. The addition of condensed tannins reduced N mineralization and nitrification. We found evidence that the use of condensed tannins might not be a suitable option to mitigate N2O emissions. However, soil CH4 emissions can be abated. The increases in soil respiration suggest that tannins affect soil microorganisms, and the effects on CH4 and N2O could be related to the variation in the soil microbiome, which requires further clarification.

Milk carbon footprint of silvopastoral dairy systems in the Northern Peruvian Amazon.

The objective of this study was to estimate the carbon footprint (CF) of milk production (in kg of CO2 equivalents (CO2e) per kg of fat and protein corrected milk (FPCM)) in dairy farms of the San Martín region, in the Peruvian Amazon. A cradle-to-farm gate characterization and analysis were carried out on eight representative dairy farms. Greenhouse gas (GHG) emissions were estimated using equations, following the 2019 refinement of the 2006 IPCC Guidelines. The results showed an average milk production of 9.7 ± 0.82 L milk/cow/day, Gyr x Holstein crosses as the predominant breed, use of cultivated grasses such as Brachiaria brizantha, living fences (Guazuma ulmifolia Lam) as the predominant silvopastoral arrangement, and low level of external inputs such as feed or grain additives. In relation to CF, an average value of 2.26 ± 0.49 kg CO2e/kg FPCM was obtained, with enteric fermentation being the most important source (1.81 ± 0.51 kg CO2e/kg FPCM), followed by manure management, land use, and energy/transport (0.26 ± 0.06, 0.14 ± 0.04, and 0.05 ± 0.04 kg CO2e/kg FPCM, respectively). Differences were found between farmers, obtaining lower CF values (1.76 vs 3.09 kg CO2e/kg FPCM) on farms with better feed quality, higher production levels, and a higher percentage of lactating animals compared to dry cows. It is concluded that dairy farms in the Peruvian Amazon region can reduce their emissions if they improve their current feeding practices.

Pasture management and greenhouse gases emissions

Pastures are important environments worldwide because they offer many ecosystem services and sustain meat and milk production. However, pastures ecosystems are responsible for greenhouse gas (GHG) emission. The major GHGs include CO2, CH4, and N2O. The present review summarizes GHG emission from pasture ecosystems and discusses strategies to mitigate this problem. In pastures, emissions originate from animal excretion, fertilization, and organic matter decomposition. Emissions of specific gases can be measured based on certain factors that were recently updated by the United Nation's Intergovernmental Panel on Climate Change in 2019. Urine is the main source of N2O emission. Forage structure is an important factor driving GHG transport. Forage fiber content and animal intake are the key drivers of enteric CH4 emission, and the introduction of forage legumes in pasture systems is one of the most promising strategy to mitigate GHG emission.

Greenhouse gas emissions from cattle dung depositions in two Urochloa forage fields with contrasting biological nitrification inhibition (BNI) capacity.

Grazing-based production systems are a source of soil greenhouse gas (GHG) emissions triggered by excreta depositions. The adoption of Urochloa forages (formerly known as Brachiaria) with biological nitrification inhibition (BNI) capacity is a promising alternative to reduce nitrous oxide (N2O) emissions from excreta patches. However, how this forage affects methane (CH4) or carbon dioxide (CO2) emissions from excreta patches remains unclear. This study investigated the potential effect of soils under two Urochloa forages with contrasting BNI capacity on GHG emissions from cattle dung deposits. Additionally, the N2O and CH4 emission factors (EF) for cattle dung under tropical conditions were determined. Dung from cattle grazing star grass (without BNI) was deposited on both forage plots: Urochloa hybrid cv. Mulato and Urochloa humidicola cv. Tully, with a respectively low and high BNI capacity. Two trials were conducted for GHG monitoring using the static chamber technique. Soil and dung properties and GHG emissions were monitored in trial 1. In trial 2, water was added to simulate rainfall and evaluate GHG emissions under wetter conditions. Our results showed that beneath dung patches, the forage genotype influenced daily CO2 and cumulative CH4 emissions during the driest conditions. However, no significant effect of the forage genotype was found on mitigating N2O emissions from dung. We attribute the absence of a significant BNI effect on N2O emissions to the limited incorporation of dung-N into the soil and rhizosphere where the BNI effect occurs. The average N2O EFs was 0.14%, close to the IPCC 2019 uncertainty range (0.01-0.13% at 95% confidence level). Moreover, CH4 EFs per unit of volatile solid (VS) averaged 0.31 g CH4 kgVS-1, slightly lower than the 0.6 g CH4 kgVS-1 developed by the IPCC. This implies the need to invest in studies to develop more region-specific Tier 2 EFs, including farm-level studies with animals consuming Urochloa forages to consider the complete implications of forage selection on animal excreta based GHG emissions.

Biochar impacts on soil chemical properties, greenhouse gas emissions and forage productivity: A field experiment.

Biochar is a promising alternative to agricultural productivity and climate change mitigation. However, quantitative data are needed to better understand the productivity and greenhouse gas (GHG) emissions from agricultural fields amended with biochar. To assess the impacts of the four biochars on soil properties, forage productivity, and GHG emissions, a 1-year field experiment was conducted in a Humic Haploxerands (Andisol). Three manure-derived biochars and one wood residue biochar (all pyrolyzed at 550 °C) were applied at rates of 1% (equivalent to 11 t ha-1) in two parallel and independent experiments. The changes in (i) soil chemical properties and yield of Sorghum sudangrass (S. bicolor×S. bicolor var. Sudanese) and (ii) soil CO2 and N2O emissions were monitored. Two controls, with and without NPK, were included. The added amendments produced from residues of poultry and pig systems increased soil pH by 0.73 and 0.19 units, respectively. Increased sorghum yield were associated with fertilizer and the liming potential of the added biochar. Soil total carbon (TC) increased with the addition of different biochars, especially during the wood biochar treatment. Biochar application, regardless of the feedstock, had no significant impact on the cumulative soil CO2 emitted after a year. Soil N2O fluxes decreased (23%-50%) in treatments containing biochars with low mineral N contents and high C stability (i.e., low H:OC and Cox:TC ratios). NPK treatment resulted in the highest N2O emissions. Wood residue-derived biochar has a great potential in mitigating climate change, reducing soil N2O emissions, and promoting soil C storage. Manure-derived biochars could be instrumental in circular economy livestock systems, where pyrolyzed animal manure can satisfy the demand for nutrients and/or liming of Andisols under sustainable forage models.

Synthesis of poly (N-vinyl pyrrolidone) (PVP) nanogels by gamma irradiation using different saturation atmospheres

Nanogels are internally crosslinked particles of nanometric size used in various fields e.g. as such as carriers in drug delivery systems. They can be produced using ionizing radiation in dilute aqueous solutions. This method is carried out in a pure polymer-solvent system, avoiding the addition of any additives such as monomers, surfactants, catalysts and crosslinking agents and no further purification step is necessary. Poly(N-vinyl pyrrolidone) (PVP K-90) nanogels were prepared by gamma irradiation in an aqueous solution. The samples were prepared in triplicate in multipurpose cobalt-60 gamma irradiator using 1, 10, 25 and 100 mM PVP solutions. Samples were irradiated in argon and nitrous oxide conditions with doses from 1 kGy up to 25 kGy with 10 kGy/h dose rate. The mean particle size (Rh) was determined by Dynamic Light Scattering (DLS) and radius of gyration (Rg) and weight-average molecular weight (Mw) by Static Light Scattering (SLS). These samples were morphologically characterized using Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM). Samples prepared with 100 mM PVP K-90 solution formed macroscopic gels, in the samples obtained with 25 mM PVP K-90 solution there was a prevalence of intermolecular crosslinking. On the other hand, in the samples generated with 10 mM PVP K-90 solution, there was a predominance of intramolecular crosslinking demonstrated in the tendency to: decrease in the radius of gyration (Rg), in the constancy of the weight-average molecular weight (Mw), in the increase in polymer coil density (ρcoil), in the Rg/Rh ratio (shape factor) around 1.0 indicating homogenous, internally cross-linked spheres, in the high relief spherical structures observed in the AFM images and in the spherical particles with high contrast observed in the TEM images. The saturation of the samples with nitrous oxide doubled formation of hydroxyl radicals, favoring the generation of polymeric radicals. Higher average number of radicals in each macromolecule contributed to the higher number of intramolecular crosslinks.

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

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 biochemical 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.

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.

Maize-Brachiaria intercropping: A strategy to supply recycled N to maize and reduce soil N2O emissions?

Nitrogen use in agriculture directly impacts food security, global warming, and environmental degradation. Forage grasses intercropped with maize produce feed for animals and or mulch for no-till systems. Forage grasses may exude nitrification inhibitors. It was hypothesized that brachiaria intercropping increases N recycling and maize grain yield and reduces nitrous oxide (N2O) emissions from soil under maize cropping. A field experiment was set up in December 2016 to test three cropping system (maize monocropped, maize intercropped with Brachiaria brizantha or with B. humidicola) and two N rates (0 or 150 kg ha-1). The grasses were sown with maize, but B. humidicola did not germinate well in the first year. B. brizantha developed slowly during the maize cycle because of shading but expanded after maize was harvested. The experiment was repeated in 2017/2018 when B. humidicola was replanted. N2O and carbon dioxide (CO2) emissions, maize grain yield and N content were measured during the two seasons. After the first maize harvest, the above- and below-ground biomass, C and N content of B. brizantha grown during fall-winter, and the biological nitrification inhibition potential of B. brizantha were evaluated. Maize yield responded to N fertilization (5.1 vs. 9.8 t ha-1) but not to brachiaria intercropping. B. brizantha recycled approximately 140 kg N ha-1 and left 12 t dry matter ha-1 for the second maize crop. However, the 2017/18 maize yields were not affected by the N recycled by B. brizantha, whereas N2O emissions were higher in the plots with brachiaria, suggesting that part of the recycled N was released too early after desiccation. Brachiarias showed no evidence of causing nitrification inhibition. The strategy of intercropping brachiarias did not increase maize yield, although it added C and recycled N in the system.

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.

Nitrous oxide as an adjunctive therapy in major depressive disorder: a randomized controlled double-blind pilot trial

Objective: Major depressive disorder (MDD) is related to glutamatergic dysfunction. Antagonists of glutamatergic N-methyl-D-aspartate receptor (NMDAR), such as ketamine, have antidepressant properties. Nitrous oxide (N2O) is also a NMDAR antagonist. Thus, this study aimed to evaluate the effects of augmenting antidepressant treatment with N2O. Methods: This double blind, placebo-controlled randomized parallel pilot trial was conducted from June 2016 to June 2018 at the Hospital das Clínicas, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo. Twenty-three subjects with MDD (aged 18 to 65, on antidepressants, with a score > 17 on the 17-item-Hamilton Depression Rating Scale [HAM-D17]) received 50% N2O (n=12; 37.17±13.59 years) or placebo (100% oxygen) (n=11; 37.18±12.77 years) for 60 minutes twice a week for 4 weeks. The primary outcome was changes in HAM-D17 from baseline to week 4. Results: Depressive symptoms improved significantly in the N2O group (N2O: from 22.58±3.83 to 5.92±4.08; placebo: from 22.44±3.54 to 12.89±5.39, p < 0.005). A total of 91.7% and 75% of the N2O group subjects achieved response (≥ 50% reduction in HAM-D17 score) and remission (HAM-D17 < 7), respectively. The predominant adverse effects of N2O treatment were nausea, vomiting, and headache. Conclusion: N2O treatment led to a statistically significant reduction in HAM-D17 scores compared to placebo. Clinical trial registration: Brazilian Register of Clinical Trials, RBR-5rz5ch

Improved accuracy and reduced uncertainty in greenhouse gas inventories by refining the IPCC emission factor for direct N2 O emissions from nitrogen inputs to managed soils.

Most national GHG inventories estimating direct N2 O emissions from managed soils rely on a default Tier 1 emission factor (EF1 ) amounting to 1% of nitrogen inputs. Recent research has, however, demonstrated the potential for refining the EF1 considering variables that are readily available at national scales. Building on existing reviews, we produced a large dataset (n = 848) enriched in dry and low latitude tropical climate observations as compared to former global efforts and disaggregated the EF1 according to most meaningful controlling factors. Using spatially explicit N fertilizer and manure inputs, we also investigated the implications of using the EF1 developed as part of this research and adopted by the 2019 IPCC refinement report. Our results demonstrated that climate is a major driver of emission, with an EF1 three times higher in wet climates (0.014, 95% CI 0.011-0.017) than in dry climates (0.005, 95% CI 0.000-0.011). Likewise, the form of the fertilizer markedly modulated the EF1 in wet climates, where the EF1 for synthetic and mixed forms (0.016, 95% CI 0.013-0.019) was also almost three times larger than the EF1 for organic forms (0.006; 95% CI 0.001-0.011). Other factors such as land cover and soil texture, C content, and pH were also important regulators of the EF1 . The uncertainty associated with the disaggregated EF1 was considerably reduced as compared to the range in the 2006 IPCC guidelines. Compared to estimates from the 2006 IPCC EF1 , emissions based on the 2019 IPCC EF1 range from 15% to 46% lower in countries dominated by dry climates to 7%-37% higher in countries with wet climates and high synthetic N fertilizer consumption. The adoption of the 2019 IPCC EF1 will allow parties to improve the accuracy of emissions' inventories and to better target areas for implementing mitigation strategies.

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)