Mercury concentrations and differences in isotopic niches of fish from upstream and downstream of an Amazon reservoir dam.

Reservoir construction promotes many environmental impacts, including the enhancement of mercury concentrations in fish. The processes that can influence mercury concentrations in fish in Amazonian reservoirs are still little explored in depth, especially when we consider the possible particularities of the ecosystems in question. This study aims to investigate how mercury concentrations in fish could be influenced by the Tucuruí dam, considering possible changes in their feeding and trophic position according to the dam position (up or downstream). Fish were sampled upstream and downstream of the Tucuruí reservoir, and total mercury (THg) and stable isotopes of carbon and nitrogen (δ15N and δ13C) were measured in muscles. We observed three different Hg bioaccumulation patterns influenced by the dam. These differences occurred due to species trophic niche changes corroborated by the isotope analysis. Higher THg concentrations downstream compared to those upstream ones were only observed for Geophagus proximus. On the contrary, Plagioscion squamosissimus, from downstream, presented lower concentrations than upstream ones. The isotopic niche of these two species presented different changes according to the sampled site. THg biomagnification was higher upstream compared to downstream, considering that the regression slope was approximately two times higher upstream versus downstream. THg concentrations in fish were explained by the differences in their feeding habits according to their location in relation to the dam. The difference in THg biomagnification was able to reflect differences in structure of the food web chain in ecosystems under the dam's influence.

Fate and Trophic Transfer of Rare Earth Elements in a Tropical Estuarine Food Web.

We sampled abiotic and food web components in an impacted estuarine system to assess the transfer and fate of rare earth elements (REE). REE (based on dry weight) were measured in sediments, suspended particulate matter (SPM), and organisms from different trophic levels. The highest ∑REE concentrations were measured in sediments (180 ± 4.24 mg kg-1) and SPM (163 ± 12.6 mg kg-1). Phytoplankton (45.7 ± 5.31 mg kg-1), periphyton (51.6 ± 1.81 mg kg-1), and zooplankton (68.5 ± 1.27 mg kg-1) are the major sources of exposure and transfer of REE to the food web. REE concentrations were several orders of magnitude lower in bivalves, crustaceans, and fish (6.01 ± 0.11, 1.22 ± 0.18, and 0.059 ± 0.003 mg kg-1, respectively) than in plankton. The ∑REE declined as a function of the trophic position, as determined by functional feeding groups and δ15N, indicating that REE were subject to trophic dilution. Our study suggests that the consumption of seafood is unlikely to be an important source of REE for humans. However, given the numerous sources of dietary introduction of REE, they should be monitored for a possible harmful cumulative effect. This study provides new key information on REE's baseline concentrations and trophic transfers and patterns.

Effects of illegal gold mining on Hg concentrations in water, Pistia stratiotes, suspended particulate matter, and bottom sediments of two impacted rivers (Paraíba do Sul River and Muriaé River), Southeastern, Brazil.

Recent reports of illegal small-scale alluvial gold mining activities (locally called garimpo) by miners working on rafts in the Paraíba do Sul River (PSR) and in one of its tributaries (Muriaé River (MR)) have raised concerns about Hg contamination. This study aimed to evaluate the impact of garimpo activities on Hg contamination in three environmental compartments. Water, sediment, and aquatic macrophytes (Pistia stratiotes) were sampled during the rainy season in PSR, forming a 106-km transect from the point where garimpo rafts were seen and/or seized by the Federal Police. They were also sampled in the MR. Total and dissolved mercury (Hg) concentrations in water and total Hg in the suspended particulate matter (SPM) sampled in the PSR increased by 1.7, 1.5, and 2.1 times at the points where the rafts were seen compared to the point immediately upstream. In the MR, Hg concentrations were higher than those in the PSR, but most values in the environmental compartments were below the safe limits (174-486 ng∙g-1, threshold and probable effect level, respectively), with the exception of Hg in the SPM of one of the MR sampling points (256 ng∙g-1) and the mining tailings (197 ng∙g-1). Sediment granulometry was exponentially associated with Hg concentrations in the sediment (R2 = 0.75, p < 0.0001) and is also essential to understand the physical impacts of garimpo on PSR. Future studies should focus on assessing the seasonal variability of Hg concentrations in the studied compartments, especially if garimpo is identified during the dry season.

Comparative metal accumulation and toxicogenetic damage induction in three neotropical fish species with distinct foraging habits and feeding preferences.

Environmental pollutants affect fish species differently because their routes of exposure make them more critical to a specific group regarding foraging habits or food preferences. However, the association between local problems and environmental conditions makes a particular species more suitable for use in monitoring programs. Thus, this study compared muscle accumulation of metals (Al, Ba, Cr, Cu, Fe, Mn, Ti and Zn) and toxicogenetic damage to three neotropical species from the Itapemirim River Basin (Brazil) with distinct foraging habits and feeding preferences: Geophagus brasiliensis (benthopelagic - omnivorous); Harttia sp. (benthic - detritivorous); and Leporinus copellandii (pelagic - omnivorous). There was seasonal influence on muscle metal concentrations: Ba and Mn concentrations in G. brasiliensis, Cr in Harttia sp. and Zn, Al and Fe in L. copellandii increased during the rainy season. G. brasiliensis was the most sensitive species, since it had a statistically higher prevalence of erythrocytic nuclear abnormalities, which was influenced by seasonality. This result might be an effect of its benthopelagic habits, which favors contact with a larger group of contaminants due to its interaction with both water column and sediment. The present study showed the differential sensitivity of fish species and that the combination of chemical analysis of pollutants with evaluation of toxicogenetic responses helps to choose the best species for field studies.

Relative effects of nutrient emission from intensive cage aquaculture on the semiarid reservoir water quality.

The effects of cage aquaculture on freshwater ecosystems are determined by multiple farming and environmental variables, and thus, the assessment of a wide range of abiotic and biotic variables enables better understanding of the impacts generated by this nutrient source. This study was carried out at Castanhão reservoir located in the State of Ceará, which is the largest Brazilian producer of Nile tilapia in cage systems, wherein about 8000 reservoirs provide a vast area to expand not only this important socio-economic but also pollution-prone activity. Nutrient mass budget, water quality monitoring, hydrodynamic characterization, and elemental/stable isotopic composition of end-member products were measured in cage aquaculture and other reservoir areas in order to determine the relative effects on reservoir conditions. Nutrient budgets showed that 34% of the artificial feed was lost to the water column but water quality monitoring and isotopic composition analysis suggested that the cages were not extensively impacting the water quality probably because of the physiographic and hydrodynamic features of the cage site.

Mismatch between sediment metal distribution and pollution source gradient: a case study of a small-size drainage basin (Southeastern Brazil).

Metal contamination in aquatic environments may occur when the anthropogenic emission exceeds the natural contribution although other factors might influence the metal distribution. In the small-size Macaé river basin, most of the metal emission was originated from anthropogenic sources suggesting a contamination status. Total and exchangeable metal concentrations were determined in sediments from the pristine upstream to the urban estuary and compared to the metal content in rocks to establish contamination and background concentrations. The enrichment of Pb in sediments compared to the regional background and high exchangeable concentrations suggest the influence of anthropogenic sources on Pb distribution. Al, Fe Mn, Zn, Ba, Cu, Cr, Ni concentrations in sediments were similar to the rock content and the values were considered regional background. Spatial distribution did not follow the whole-basin emission source gradient suggesting that despite actual anthropogenic sources, the sediment mineralogy and basin geomorphology might influence the sediment metal distribution.

Unveiling mercury levels: Trophic habits influence on bioaccumulation in two Otariid species.

Mercury, a toxic metal released by various human activities, exerts environmental stress through its bioaccumulation and biomagnification, particularly in marine habitats. South American fur seals (Arctocephalus australis) and sea lions (Otaria flavescens) reproduce on the Atlantic coast of Uruguay. As top predators, they can accumulate toxic levels of mercury and are often used as sentinel species for monitoring ecosystem health. Fur seals prey on pelagic species, such as fish and squid, while sea lions consume coastal-benthic prey. We analyzed the total mercury concentration (THg) in hair and the trophic habits (δ13C and δ15N) of females from both species. The average THg concentration in adult female sea lions (30.5 ± 9.3 µg/g dry weight) was significantly higher than in fur seals (6.3 ± 2.5 µg/g dry weight). Additionally, the mean δ15N and δ13C values were significantly higher in sea lion (δ15N: 19.2 ± 0.6‰, δ13C: -13.8 ± 0.2‰) compared to fur seals (δ15N: 16.5 ± 0.5‰, δ13C: -15.5 ± 0.6‰). Our results suggest that different trophic levels and feedings areas affect the THg concentration in Uruguayan Otariids. Notably, at the intraspecific level, the THg concentration in sea lions increased with δ13C values, suggesting a link to coastal feeding habits. This indicates that coastal feeding behaviors, compared to feeding in pelagic environments, enhance mercury bioaccumulation in Otariids along the Uruguayan coast, with the discharge of freshwater from the Río de la Plata (one of the largest estuaries in South America) basin identified as a potential mercury source. THg concentrations found in female sea lion hair are the highest reported in Otariids globally. Mercury levels exceeded toxic thresholds observed in other mammals and could pose significant health risks. Our findings may explain why sea lions were particularly affected by the avian influenza outbreak in Uruguay compared to fur seals. Monitoring the declining sea lion population is crucial, making our results significant for integrated conservation and management strategies.

First record of mercury concentrations and stable isotopes (13C & 15N) in albacore (Thunnus alalunga) from the Western Equatorial Atlantic Ocean.

This paper reports the first record of total mercury (THg) concentrations in albacore (Thunnus alalunga), one of the main tuna species caught from the Western Equatorial Atlantic Ocean and presents a preliminary comparison with other regions and tuna species. Mean, standard deviation and range of concentrations in T. alalunga (515 ± 145 ng g-1 ww; 294-930 ng g-1 ww) with 92 % being of methyl-Hg, are higher than in albacore from other Atlantic Ocean subregions despite their smaller body size. These concentrations are similar to those from the Pacific and Indian oceans, but lower than in the Mediterranean. Compared to other sympatric tuna species, concentrations are higher than those in T. albacares and similar to T. obesus. These results are discussed considering the potential differences in stable isotope values (13C and 15N) of T. alalunga populations from multiple oceanic areas and compared to other tuna species worldwide.

Geochemical fractionation of trace metals and ecological risk assessment of surface sediments in Sepetiba Bay, Brazil.

The Sepetiba Bay (Southeast Brazil) is a known Cd- and Zn-contaminated site that received spills of a large slag pile leachate from a Zn smelter. With important harbors, Sepetiba Bay demands periodic dredging operations which affect the mobility of the metals. The main goal of this work was to assess metal mobility in sediments and its associated toxicity in a fictive dredging area, to evaluate the risks of the operation. To achieve this goal, 18 superficial sediment samples were collected and characterized for pH and Eh. Sediments were analyzed for grain size, organic carbon, and total nitrogen, and metal mobility was evaluated with a sequential extraction procedure, proposed by the European Community Bureau of Reference (BCR). The results demonstrate that Cd and Zn are mainly associated with the exchangeable fraction (mean concentrations 1.4 mg kg-1 and 149.4 mg kg-1, respectively) and reducible fractions (mean concentrations 0.3 mg kg-1 and 65.5 mg kg-1, respectively), while Fe, Cr, Cu, Ni, and Al were associated with the residual fraction. Metals in the residual fraction are probably associated with the mineral lattice of the sediment and should not represent an environmental risk for the biota. The application of the enrichment factor and three risk assessment indexes (Risk Assessment Code, Risky Pollution Index, and Bioavailability Risk Assessment Index) show that the sediments are considerably enriched in metals that constitute a relevant risk for the sediment biota. In the case of dredging operations, Cd and Zn should be released to the overlying waters and be available to organisms, threatening the whole ecosystem. The proposed approach was shown to be much more precise than what is frequently presented in the Environmental Impact Assessments that only consider the threshold limits of the legislation.

Acute toxicity bioassay with the amphipod, Grandidierella bonnieroides S. after exposure to sediments from an urban estuary (Macaé River Estuary, RJ, Brazil).

Acute toxicity to Grandidierella bonnieroides and physicochemical analysis were used for quality assessment of the sediment of the Macaé River urban estuary, located in the Brazilian coast where rapid socioeconomic growth has been induced by offshore oil and gas exploration at the Campos Basin. Sediment samples were collected during four events in four sampling sites of the estuary and also in a control site. Organism mortality after exposure to the estuarine sediments was, on average, 30 % a value higher than in the control site where it was 10 %. This result together with the physicochemical analysis suggests an initial toxicity condition of the sediments from this aquatic coastal environment.

Global decrease in blood lead concentrations due to the removal of leaded gasoline.

Lead (Pb) is a chemical element with extreme toxicity that is classified as one of the ten chemicals of most significant concern to human health. The main problem involving Pb is its use as a fuel additive (tetraethyllead - TEL) at a global level, which raised the atmospheric Pb concentrations. It is estimated that between 80 and 90% of the atmospheric Pb in large cities came from the use of TEL, and as a consequence, it was also the main source responsible for human exposure to the element. Therefore, this work aimed to evaluate, through a systematic review, the blood concentrations of Pb in scientific articles published in the first two decades of the 2000s to compare the global and regional trends of each continent over time. Our data show the importance of removing TEL in decreasing human exposure to Pb worldwide. We observed exponentially decreasing blood Pb concentrations over the years after additive removal on all continents, resulting in a global trend which TEL's use was the major process governing human exposure worldwide. In addition, the results also showed that, despite the removal of Pb additives lowering levels of human blood Pb, the general population remains exposed to the element through exogenous and endogenous sources. The exhaust Pb particles were deposited into the environment in proportion to the traffic flows, and the legacy of Pb in the environment requires novel primary prevention remedy to curtail exposure.

The Paraíba do Sul River Basin and its coastal area as a study model of the mercury cycle: A meta-analytical review of three decades of research.

The Paraíba do Sul River (PSR) Basin is a crucial drainage basin in Southeast Brazil, being the most industrialized and densely populated region in the country. Over the last three decades, the basin has been the subject of numerous studies due to its long history of mercury (Hg) contamination. This makes the PSR Basin an excellent model to evaluate Hg cycling, which is a priority for signatory countries of the Minamata Convention, which includes Brazil. This review compiled data on Hg from five environmental compartments (animals, plants, sediment, suspended particulate matter (SPM), and water), three different sectors (upper, middle, and lower) and five different ecosystems (reservoir, mangrove, fluvial, estuarine, and coastal) from 60 published studies, aiming to understand the Hg cycling through meta-analyses. The highest concentrations of Hg were observed in the upper and middle sectors of the basin, which are areas with high industrialization and urbanization levels. Among the evaluated ecosystems, hydropower reservoirs showed the highest medians and were also frequent in the upper and middle portions of the PSR basin. Over the years, all environmental compartments showed a decline in Hg concentrations due to the implementation of federal and state environmental policies. The main source of Hg for the basin was Hg-rich soils from past activities (such as artisanal small-scale gold mining and the use of organomercurial fungicides in sugarcane plantations). These results can assist decision-makers in the management of the basin's ecosystems and can also be used to evaluate the effectiveness of implementing the Minamata Convention in the region.

Land-use changes in Amazon and Atlantic rainforests modify organic matter and black carbon compositions transported from land to the coastal ocean.

This study assessed black carbon (BC) dynamics, concentrations, and the organic matter (OM) isotopic carbon composition in northeastern South America drainage basin coastal sediments. Paraíba do Sul (PSR; Atlantic Rainforest, Brazil) coastal sediments displayed more 13C-enriched values (-22.6 ± 1.3 ‰ [n = 13]) than Amazon and Sinnamary (Amazon Rainforest in French Guiana and Brazil) sediments (-25.0 ± 3.1 ‰ [n = 14] and - 26.1 ± 1.0 ‰ [n = 6], respectively), indicating that local land-use basin changes have altered the OM composition, i.e., from natural C3 plant to C4 plants contributions. BC contents normalized to total organic carbon (TOC) content were 0.32 ± 0.24 (n = 8), 0.73 ± 0.67 (n = 6), and 0.95 ± 0.74 (n = 13) mg g-1 TOC for Amazon, Sinnamary and PSR samples, respectively, with BC sources appearing to differ according to different drainage basin vegetation covers. With increasing distance from the river mouths, BC contents exhibited different trends between the coastal zones, with values increasing for the PSR and decreasing values for the Amazon samples. BC distribution in Sinnamary coastal sediments did not display specific patterns. Regarding the Amazon coastal zone, BC contents decreased while the B6CA:B5CA ratios did not show a pattern, which could indicate that BC in the area originates from river transport (aged BC) and that the hydrophobic component of dissolved BC is removed. The BC content mostly increased in the PSR coastal zone, while the B6CA:B5CA ratios were not altered for the entire gradient, indicating the BC stability and possible atmospheric deposition of soot. Our findings indicate that different sources, transformation processes, and hydrological conditions affect BC contents within coastal zones. Continuous land cover changes in both the Amazon and Atlantic Rainforests may result in large-scale marine carbon cycling impacts.

Trace metal concentration along the Brazilian coast: An assessment of the influence of the Doce River plume.

The Fundão Dam rupture released tons of iron ore tailings into the environment. This study analyzes the long-term impacts and provides a possible scenario of Doce River (DR) plume dispersion. For this, water and surface sediment were collected in November 2019 along three Brazilian states to determine metal concentrations and δ13C and δ15N compositions. The δ13Csediment values of the DR plume showed a dispersion pattern mainly to the north but also in areas closer to the south of the DR mouth. Furthermore, the most negative values of δ13C and δ15N were observed in mud, followed by suspended particulate matter, sediment and the dissolved fraction, indicating that geological matrices are involved in the transport of organic matter coupled to metals to the ocean and pointing to the DR as the main source of metals in the region. Thus, this study highlights the need for continuous studies to monitor the environmental and biological conditions in these areas.

Evaluating total mercury and methylmercury biomagnification using stable isotopes of carbon and nitrogen in fish from the Madeira River basin, Brazilian Amazon.

The isotopic signatures of carbon in primary consumer fish species in the Madeira River basin (Western Amazon) follow a pattern, with basal species feeding mainly on C3 (e.g., vascular plants and phytoplankton). In this study with 196 specimens of 19 fish species and six trophic guilds, significant differences were found between the two main groups of primary consumers (herbivores and detritivores) in the Madeira River basin. The mercury and δ15N data indicated that the fish specimens collected in Puruzinho and Cuniã Lakes provided greater trophic magnification factors (TMFs) for this metal than those found in the corresponding rivers. In relation to total mercury (0.09-2.07 µg g-1) and methylmercury (0.05-1.91 µg g-1) concentrations, the piscivorous/carnivorous species exceeded the values recommended by the World Health Organization, with a [MeHg:THg] ratio of about 80%. Preventive and educational practices should be adopted to reduce the possible toxic effects of Hg in the riverside population, for whom fish constitutes the main protein source. Also, biomonitoring of the fish species in the Madeira River should be conducted on an ongoing basis to detect possible alterations in mercury concentrations.

Metal concentrations in the whole blood of farmers in southeast Brazil.

In this study, we measured Ni, Co, Cd, and Pb concentrations in the whole blood of farmers from southeast Brazil to address the factors influencing human exposure in this population. The factors included smoking, alcohol consumption, aging, body composition, gender, and feeding preferences, which were measured through carbon and nitrogen isotopic composition. We also calculated and compared the reference values (RVs) of the measured elements to evaluate ongoing exposure levels. We observed the influence of lifestyle habits on metal exposure; Cd levels were statistically higher in smokers, and alcohol consumption affected only Pb concentrations, with an association also observed with the frequency of alcohol ingestion. The metal levels were positively associated with both isotope values, indicating that feeding may be the dominant source of these elements in this population. We also observed the effect of endogenous sources measured through age, as increased Pb concentrations in both genders and higher Cd levels in older women, which is related to bone, kidney, and liver accumulation. The body mass index was negatively associated with Ni, Co, and Cd in women and positively in men. The negative associations may indicate that body fat may act as a reservoir for metals, reducing their availability in the blood in individuals with higher body mass and possibly influencing the assessment of exposure levels. The evaluated population presented elevated RVs for all elements: Ni 36, Co 3.3, Cd 16, and Pb 149 µg L-1. These values point to higher exposure in this population compared to other studies in Brazil and worldwide. These results emphasize an urgent need for monitoring programs for toxic substances in Brazil and evaluating possible health effects, given the ongoing environmental exposure associated with endogenous exposure and lifestyle habits that promote higher metal levels in this population.

Machine learning sheds light on physical-chemical and biological parameters leading to Abrolhos coral reef microbialization.

Microbes play a central role in coral reef health. However, the relative importance of physical-chemical and biological processes in the control of microbial biomass are unknown. Here, we applied machine learning to analyze a large dataset of biological, physical, and chemical parameters (N = 665 coral reef seawater samples) to understand the factors that modulate microbial abundance in the water of Abrolhos reefs, the largest and richest coral reefs of the Southwest Atlantic. Random Forest (RF) and Boosted Regression Tree (BRT) models indicated that hydrodynamic forcing, Dissolved Organic Carbon (DOC), and Total Nitrogen (TN) were the most important predictors of microbial abundance. The possible cumulative effects of higher temperatures, longer seawater residence time, higher nutrient concentration, and lower coral and fish biomass observed in coastal reefs resulted in higher microbial abundance, potentially impacting coral resilience against stressors.

Effects of dams on As and Hg concentrations in three southeastern Brazil fluvial systems: Ocean inputs, sources and seasonal dynamics among environmental compartments.

Damming rivers for hydropower generation interferes in the flow of water bodies and, consequently, in trace element biogeochemistry and transport. This study focused on the effects of dams on the seasonal dynamics of arsenic (As) and mercury (Hg) in three fluvial systems (Itabapoana River, Flechas Channel and Paraíba do Sul River) and on the input of these elements to the ocean. The elements were evaluated in suspended particulate matter (SPM), surface sediments, and the roots of the aquatic macrophyte Eichhornia crassipes. Our results showed that the proximity of the dams in the Flechas Channel and Rio Itabapoana in relation to their mouth (distances of 4 km and 58 km, respectively) changed As and Hg seasonal dynamics in the environmental compartments analyzed, with the Flechas Channel being the most impacted area. In contrast, the lower part of the Paraíba do Sul River that has more distant dams to its mouth (distance of 184 km) did not show such marked changes, suggesting that most of the inputs are coming from the long river reach. The isotopic and elemental composition of organic matter indicated the soils of native forests as the main source of trace elements to the water bodies. Flow rate was the main driver controlling As and Hg ocean inputs, with higher inputs observed in the Paraíba do Sul River (9.69 and 0.59 t∙year-1, respectively) compared to the other assessed fluvial systems. Also, this study demonstrated that, if a dam is closer to the mouth of a river, less contaminants will be input.

Mangrove microbiome reveals importance of sulfur metabolism in tropical coastal waters.

Mangroves under macro-tidal regimes are global carbon sequestration hotspots but the microbial drivers of biogeochemical cycles remain poorly understood. Here, we investigate the drivers of mangrove microbial community composition across a porewater-creek-estuary-ocean continuum. Observations were performed on the Amazon region in one of the largest mangrove systems worldwide with effective sequestration of organic carbon buried in soils and dissolved carbon via outwelling to the ocean. The potential export to the adjacent oceanic region ranged from 57 to 380 kg of dissolved and particulate organic carbon per second (up to 33 thousand tons C per day). Macro tides modulated microbial communities and their metabolic processes, e.g., anoxygenic phototrophy, sulfur, and nitrogen cycling. Respiration, sulfur metabolism and dissolved organic carbon (DOC) levels were linked to functional groups and microbial cell counts. Total microbial counts decreased and cyanobacteria counts peaked in the spring tide. The microbial groups driving carbon, nitrogen, sulfur and methane cycles were consistent across all spatial scales. Taxonomic groups engaged in sulfur cycling (Allochromatium, Desulfovibrio, and Thibacillus) within mangroves were abundant at all scales. Tidally-driven porewater exchange within mangroves drove a progressive increase of sulfur cycle taxonomic groups and their functional genes both temporally (tidal cycles) and spatially (from mangrove porewater to continental shelf). Overall, we revealed a unified and consistent response of microbiomes at different spatial and temporal scales to tidally-driven mangrove porewater exchange.

Reducing care time after implementing protocols for acute ischemic stroke: a systematic review.

BACKGROUND: The treatment of acute ischemic stroke with cerebral reperfusion therapy requires rapid care and recognition of symptoms. OBJECTIVE: To analyze the effectiveness of implementing protocols for acute ischemic stroke in reducing care time. METHODS: Systematic review, which was performed with primary studies in Portuguese, English, and Spanish published between 2011 and 2020. INCLUSION CRITERIA: study population should comprise people with acute ischemic stroke and studies should present results on the effectiveness of using urgent care protocols in reducing care time. The bibliographic search was conducted in June 2020 in the LILACS, MEDLINE, Embase, Scopus, CINAHL, Academic Search Premier, and SocINDEX databases. The articles were selected, and data were extracted by two independent reviewers; the synthesis of the results was performed narratively. The methodological quality of articles was evaluated through specific instruments proposed by the Joanna Briggs Institute. RESULTS: A total of 11,226 publications were found, of which 35 were included in the study. Only one study reported improvement in the symptoms-onset-to-door time after protocol implementation. The effectiveness of the therapeutic approach protocols for ischemic stroke was identified in improving door-to-image, image-to-needle, door-to-needle and symptoms-onset-to-needle times. The main limitation found in the articles concerned the lack of clarity in relation to the study population. CONCLUSIONS: Several advances have been identified in in-hospital care with protocol implementation; however, it is necessary to improve the recognition time of stroke symptoms among those who have the first contact with the person affected by the stroke and among the professionals involved with the prehospital care.

ANTECEDENTES: O tratamento do acidente vascular cerebral (AVC) isquêmico com terapia de reperfusão requer rápido atendimento e reconhecimento dos sintomas. OBJETIVO: Analisar a efetividade da implementação de protocolos para AVC isquêmico agudo na redução do tempo de atendimento. MéTODOS: Revisão sistemática realizada com estudos primários em português, inglês e espanhol publicados entre 2011 e 2020. Critérios de inclusão: a população do estudo foi constituída por pessoas com AVC isquêmico agudo e estudos que apresentassem resultados sobre a efetividade da implantação de protocolos no tempo de atendimento. A pesquisa bibliográfica foi realizada em junho de 2020 nas bases de dados LILACS, MEDLINE, Embase, Scopus, CINAHL, Academic Search Premier e SocINDEX. A seleção dos artigos e a extração dos dados foram feitas por dois revisores independentes; a síntese dos resultados foi feita de forma narrativa. A qualidade metodológica dos artigos foi avaliada por meio de instrumentos do Joanna Briggs Institute. RESULTADOS: Foram encontradas 11.226 publicações, das quais 35 foram incluídas no estudo. Apenas um estudo relatou melhora no tempo início dos sintomas-porta após a implementação do protocolo, no entanto, foi efetiva na melhora dos tempos porta-imagem, imagem-agulha, porta-agulha e início dos sintomas-agulha. A principal limitação encontrada nos artigos diz respeito à falta de clareza quanto à população de estudo. CONCLUSõES: Vários avanços foram identificados no atendimento intra-hospitalar com implantação de protocolo; porém, é necessário melhorar o tempo de reconhecimento dos sintomas do AVC entre aqueles que têm o primeiro contato com a pessoa acometida e entre os profissionais envolvidos com o atendimento pré-hospitalar.