R S U i F H P a b c d e f g h i R A h 0 B ev Bras Anestesiol. 2017;67(4):376---382 REVISTA BRASILEIRA DE ANESTESIOLOGIA Publicação Oficial da Sociedade Brasileira de Anestesiologia www.sba.com.br CIENTIFIC ARTICLE se of ultrasound for gastric volume evaluation after ngestion of different volumes of isotonic solution� lora Margarida Barra Bisinottoa,b,c,d,∗, Aline de Araújo Navese, ellen Moreira de Limaf,g, Ana Cristina Abdu Peixotoe,h, Gisele Caetano Maiab, aulo Pacheco Resende Juniorb, Laura Bisinotto Martins i, Luciano A. Matias da Silveirab Sociedade Brasileira de Anestesiologia, Rio de Janeiro, RJ, Brazil Universidade Federal do Triângulo Mineiro (UFTM), Hospital de Clínicas, Uberaba, MG, Brazil Universidade Estadual Paulista ‘‘Júlio de Mesquita Filho’’ (UNESP), Botucatu, SP, Brazil Universidade Federal do Triângulo Mineiro (UFTM), Disciplina de Anestesiologia, Uberaba, MG, Brazil Universidade Federal do Triângulo Mineiro (UFTM), Serviço de Radiologia e Diagnóstico, Uberaba, MG, Brazil Universidade Federal do Triângulo Mineiro (UFTM), Serviço de Radiologia e Diagnóstico, Uberaba, MG, Brazil Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG), Belo Horizonte, MG, Brazil Universidade Federal do Triângulo Mineiro (UFTM), Programa de Pós-Graduação em Ciências da Saúde, Uberaba, MG, Brazil Universidade de Ribeirão Preto (UNAERP), Curso de Graduação em Medicina, Ribeirão Preto, SP, Brazil eceived 29 January 2016; accepted 26 July 2016 vailable online 9 April 2017 KEYWORDS Bronchoaspiration; Gastric ultrasound; Preoperative fasting Abstract Background and objectives: The current preoperative fasting guidelines allow fluid intake up to 2 h before surgery. The aim of this study was to evaluate the gastric volume of volunteers after an overnight fast and compare it with the gastric volume 2 h after ingestion of 200 and 500 mL of isotonic solution, by means of ultrasound assessment. Method: Eighty volunteers underwent gastric ultrasound at three times: after 8 h of fasting; 2 h after ingestion of 200 mL isotonic saline, followed by the first scan; and on another day, 2 h after ingestion of 500 mL of the same solution after an overnight fast. The evaluation was quan- titative (antrum area and gastric volume, and the ratio of participants’ gastric volume/weight) and qualitative (absence or presence of gastric contents on right lateral decubitus and supine positions. A p-value < 0.05 was considered significant). Results: There was no difference in quantitative variables at measurement times (p > 0.05). Five volunteers (6.25%) had a volume/weight over 1.5 mL kg−1 at fasting and 2 h after ingestion of 200 mL and 6 (7.5%) after 500 mL. Qualitatively, the presence of gastric fluid occurred in more volunteers after fluid ingestion, especially 500 mL (18.7%), although not statistically significant. � Study performed at the Hospital de Clínicas da Universidade Federal do Triângulo Mineiro (UFTM), Uberaba, MG, Brazil. ∗ Corresponding author. E-mail: flora@mednet.com.br (F.M. Bisinotto). ttp://dx.doi.org/10.1016/j.bjane.2017.03.001 104-0014/© 2016 Sociedade Brasileira de Anestesiologia. Published by Elsevier Editora Ltda. This is an open access article under the CC Y-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). dx.doi.org/10.1016/j.bjane.2017.03.001 http://www.sba.com.br http://crossmark.crossref.org/dialog/?doi=10.1016/j.bjane.2017.03.001&domain=pdf mailto:flora@mednet.com.br dx.doi.org/10.1016/j.bjane.2017.03.001 http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ Use of ultrasound for gastric volume evaluation after ingestion of solution 377 Conclusion: Ultrasound assessment of gastric volume showed no significant difference, both qualitative and quantitative, 2 h after ingestion of 200 mL or 500 mL of isotonic solution com- pared to fasting, although gastric fluid content has been identified in more volunteers, especially after ingestion of 500 mL isotonic solution. © 2016 Sociedade Brasileira de Anestesiologia. Published by Elsevier Editora Ltda. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by- nc-nd/4.0/). PALAVRAS-CHAVE Broncoaspiração; Ultrassonografia gástrica; Jejum pré-operatório Uso da ultrassonografia para avaliação do volume gástrico após ingestão de diferentes volumes de solução isotônica Resumo Justificativa e objetivos: As diretrizes recentes de jejum pré-operatório permitem a ingestão de líquidos até 2 horas antes da cirurgia. O objetivo do presente estudo foi, por meio de ultra- ssonografia gástrica, avaliar o volume gástrico de voluntários após jejum noturno e comparar com o volume gástrico duas horas após a ingestão de 200 e 500 ml de solução isotônica. Método: Foram submetidos à ultrassonografia gástrica 80 voluntários em três momentos: após jejum de 8 horas; 2 horas após a ingestão de 200 ml de solução isotônica, seguida do primeiro exame; e, em outro dia, 2 horas após a ingestão de 500 ml da mesma solução, após jejum noturno. A avaliação foi quantitativa (área do antro e volume gástricos e relação volume gástrico/peso dos participantes) e qualitativa, pela ausência ou presença de conteúdo gástrico nas posições de decúbito lateral direito e supina. Foi considerado significante p < 0,05. Resultados: Não houve diferença nas variáveis quantitativas nos três momentos estudados (p > 0,05). Cinco voluntários (6,25%) apresentaram um volume/peso superior a 1,5 ml.kg−1 em jejum e 2 horas após a ingestão de 200 ml e seis (7,5%) após 500 ml. Qualitativamente, a presença de líquido gástrico ocorreu em mais voluntários após a ingestão de líquidos, principalmente de 500 ml (18,7%), embora sem significância estatística. Conclusão: O volume gástrico pela ultrassonografia não apresenta diferença significativa tanto qualitativa quanto quantitativa, 2 horas após a ingestão de 200 ml ou de 500 ml de solução isotônica em comparação com o jejum, embora conteúdo líquido gástrico tenha sido identificado em mais voluntários, principalmente após a ingestão de 500 ml de solução isotônica. © 2016 Sociedade Brasileira de Anestesiologia. Publicado por Elsevier Editora Ltda. Este é um artigo Open Access sob uma licença CC BY-NC-ND (http://creativecommons.org/licenses/by- nc-nd/4.0/). v 2 c a f m g a i a s d h t a r v Introduction Aspiration of gastric contents is a major cause of morbid- ity and mortality during general anesthesia, as well as in the intensive care unit.1---3 The risk of mortality is up to 5% and it is involved in over 9% of all deaths related to anesthesia.4,5 The presence of gastric contents at the time of anesthesia induction is an important risk factor for its occurrence, which makes the dietary restriction rule before anesthesia essential for patient safety. Although there is a controversy about the gastric residual volume, which is considered critical because this volume itself increases the risk of aspiration, studies have shown that healthy patients under fasting often have residual volume above 1.5 mL kg−1 without significantly increased risk for aspiration.6---8 During the 1980s, a patient undergoing extended periods of fasting before elective procedures was a routine practice, which still remains in various institutions. The preoper- ative fasting recommendations have become increasingly more liberal, so that the current guidelines for preopera- tive fasting9,10 encourage the ingestion of clear liquids in g a t olumes from 100 mL to unlimited quantities for adults up to h before surgery. This approach aims to reduce patient dis- omfort and hemodynamic complications during induction of nesthesia, which are often related to dehydration resulting rom prolonged fasting.11,12 The non-adherence to recom- endations may reflect a medical preference or flaws in the uidelines themselves, such as not determining the allowed mount of liquid. The clinical access to the risk of aspiration s limited due to the lack of validated non-invasive tests to ssess gastric contents. The increased use of portable ultra- ound in surgical centers aroused interest in its use as a iagnostic method for gastric content evaluation. Studies ave shown the feasibility of using ultrasound to evaluate he gastric content by measuring the antral cross-sectional rea (ACSA).13---17 Perlas et al.15 reported an almost linear elationship between ACSA and gastric volume in healthy olunteers. The aim of this study was to evaluate by ultrasound the astric volume of healthy volunteers after an overnight fast nd compare it with the gastric volume 2 h after the inges- ion of isotonic solution in different volumes. http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ 3 M A m - c d a t ( p i d s q m ( 8 i i t w o i i c p r T s b t d w t w t i a t p l c t m m T t c w s i s c i t G s a s a t c o u i f t b � ( a o S r u p 8 Q v a s t t p t t c f s d R T t w are shown in Table 1. The results of gastric content qualita- tive assessment are shown in Table 2. None of the volunteers had solid content during the examination. Regarding qualita- tive assessment of gastric contents according to the groups, Table 1 Demographic data of study participants. Mean ± standard deviation Age (years) 33.98 ± 10.73 Weight (kg) 69.82 ± 12.55 Height (m) 1.67 ± 0.09 BMI (kg m−2) 24.86 ± 3.85 Sex Male 24 78 ethod fter obtaining approval from the Ethics Research Com- ittee of the Universidade Federal do Triângulo Mineiro -- register 1.144.018 of June 19, 2015 --- and an informed onsent, this prospective cross-sectional study was con- ucted with 80 healthy volunteers. Inclusion criteria were ge between 18 and 60 years, American Society of Anes- hesiologists (ASA) physical status I and II, body mass index BMI) under 30 kg m−2 and ability to understand the study rotocol and the informed consent. Any condition that might nterfere with the gastric emptying time, such as pregnancy, iabetes, or presence of gastrointestinal disease, was con- idered an exclusion criterion. The volunteers underwent abdominal ultrasound for uantitative and qualitative analysis of gastric contents easured in three times. The first measurement time named fasting) was after an overnight period of at least h. The second time (named 200 mL + fasting) was 2 h after ngesting 200 mL of isotonic solution, which was ingested mmediately after the ultrasound examination at the first ime. The third measurement time (named 500 mL + fasting) as performed on another day. After a minimum period f 8 h of overnight fast, the volunteers ingested 500 mL of sotonic solution and after 2 h underwent ultrasound exam- nation. All isotonic solutions were the same and contained arbohydrates (8.4 g), sodium (57 mg), chloride (49 mg), otassium (46 mg), flavoring and preservatives agents, calo- ie content of 36 kcal per 200 mL, and were refrigerated. here was no restriction on ambulation after ingestion of olutions. The ultrasound assessment of gastric content was made y a professional of the Department of Radiology of the insti- ution. Tests were performed using the technique previously escribed,13---18 with a convex probe (2---5 MHz). Volunteers ere initially examined in the supine position, followed by he right lateral decubitus (RLD) position. The transducer as placed in the sagittal plane in the epigastric region and hen the antrum and gastric body were scanned by mov- ng the transducer from right to left, in order to obtain n overall qualitative impression of the cavity and gas- ric contents. A better view of the antrum is obtained in arasagittal plane just to the right of the midline. The liver eft lobe was taken as reference, previously, and the pan- reas, posteriorly. Inferior vena cava is located posterior o the pancreas. The antrum has a wall characterized by ultiple layers and its visibility was evaluated in a binary anner (visible or not) in both positions, supine and RLD. he same sonographer performed the qualitative and quan- itative assessments of the gastric antrum. The antrum was onsidered empty when showing the anterior and posterior alls juxtaposed and regarded as containing liquid when howing a cavity view with hypoechoic content inside and ts distended walls. The antrum was judged as having a olid content when appearing distended with content with haracteristics similar to ‘‘frosted glass’’ or an echogenic mage similar to liver parenchyma. Based only on this quali- ative analysis of the antrum, the patients were classified as rade zero: empty antrum in both supine and RLD positions, uggesting an empty stomach; Grade 1: presence of liquid pparent only in RLD, suggesting small amount of fluid in the tomach; Grade 2: presence of liquid contents in both supine F.M. Bisinotto et al. nd RLD positions, suggesting the presence of increased gas- ric volume. For quantitative analysis, we measured the antral ross-sectional area (ACSA) using the technique described riginally by Bolondi18 and, subsequently, by Perlas et al.13---15 sing the outer wall of the stomach. ACSA was measured n RLD using two perpendicular diameters of the antrum, rom serosa to serosa, longitudinal or craniocaudal (CC), and he anteroposterior (AP) using the ellipse formula developed y Bolondi et al.,18 in which ACSA = ((CC × AP) × �)/4, with -value = 3.14. After ACSA calculation, the stomach total volume ‘‘expected volume’’) was estimated for each subject using mathematical model previously tested and validated by ther authors,15 in which: tomach volume (mL) = 27 + 14.6 ACSA (cm2) − 1.28 age (years) With the expected volume calculation, was obtained the elationship between the volume and weight (vol/wt) of vol- nteers were obtained. Friedman ANOVA was used for statistical analysis. Sam- le size (n = 80) was calculated to obtain 95% confidence, 0% power test, and root mean square error (RMSE) = 0.25. uantitative variables, antral gastric area (cm2), gastric olume (mL), and the relationship between gastric volume nd weight (vol/wt) of subjects (mL kg−1) were initially ubjected to a descriptive analysis using measures of cen- rality and dispersion. These variables comparison between ime points (fasting, 200 mL + fasting, 500 mL + fasting) was erformed using Friedman’s nonparametric ANOVA, due to he non-normality in data assessed by the Shapiro---Wilk est. Regarding the groups qualitative evaluation of gastric ontents, an association analysis using the �2 test was per- ormed, followed by a residue analysis when the �2 test was ignificant. The significance level for the inferential proce- ures was 5%. esults he study included 84 volunteers and 80 completed all ests (240 tests), without any adverse event or delay that ould undermine the results. Participants’ characteristics Female 56 BMI, body mass index. Use of ultrasound for gastric volume evaluation after ingestion of solution 379 Table 2 Distribution of study participants regarding quali- tative assessment of gastric contents and groups. Grade 0 Grade 1 Grade 2 Fasting 65 (81.25%) 11 (13.75%) 4 (5%) 200 mL + 2 h 55 (68.75%) 14 (17.5%) 11 (13.75%) 240 F as tin g 20 0 m L + 2 h fa st in g 50 0 m L + 2 h fa st in g Friedman ANOVA ( p = 0.58) Times G as tr ic v ol um e (m L) 220 200 180 160 140 120 100 80 60 40 20 0 –20 Median 25%-75% Min-Max Figure 2 Box-plot showing the median and interquartile r ( ( r o o r 500 mL + 2 h 57 (71.25%) 8 (10%) 15 (18.75%) p = 0.07, �2 stat = 8.8. there was a higher number of subjects with Grade zero in fasting group (81.25%), Grade 1 in 200 mL + fasting group (17.5%), and Grade 2 in 500 mL + fasting group (18.75%), sug- gesting that a larger volume ingested results in increased gastric contents after 2 h of fasting. However, this associa- tion was not statistically significant (p = 0.07). There was no difference at any time point regarding the results of quantitative assessment, antral area, gastric volume, and volume/weight ratio at the three measure- ment times (p > 0.05) (Figs. 1---3). Five volunteers (6.25%) had a volume/weight ratio over 1.5 mL kg−1, both at fast- ing and 200 mL + fasting periods, and six patients (7.5%) at 500 mL + fasting (Fig. 3). None of them was the same subject in the different situations. Discussion The aim of this study was to evaluate the gastric content in healthy volunteers using real-time ultrasound. The qualita- tive evaluation results showed an increase in the percentage of subjects with liquid content 2 h after the intake of fluids, particularly with 500 mL volume in 15 subjects (18.75%) seen in the supine and RLD positions, which supports an expected gastric volume of 180 ± 83 mL.19 In the gastric volume Friedman ANOVA ( p = 0.69) Times G as tr ic a nt ra l a re a (c m 2 ) N ig ht fa st in g 20 0 m L + 2 h fa st in g 50 0 m L + 2 h fa st in g 18 16 14 12 10 8 6 4 2 0 Median 25%-75% Min-Max Figure 1 Box-plot showing the median and interquartile range for the gastric antral area in the three measurement times (p > 0.05). o s o F r m t ange for gastric volume in the three measurement times p > 0.05). antral area, expected gastric volume, and volume/weight atio) quantitative evaluation, the results obtained after the vernight fasting period did not differ from those after 2 h f ingesting 200 mL or 500 mL volumes. Additionally, these esults also confirmed the existence of variable quantities f gastric volume after the fasting period, which in some ubjects was over 1.5 mL kg−1. Gastric sonography is a novel point-of-care application f diagnostic ultrasound, which allows anesthesiologists to 3.5 5 (6.25%) F as tin g 20 0 m L + 2 h fa st in g 50 0 m L + 2 h fa st in g 5 (6.25%) 6 (7.5%) Friedman ANOVA (p = 0.58 ) Times G as tr ic v ol um e/ w ei gh t ( m L. kg –1 ) 3.0 2.5 2.0 1.5 1.0 0.5 0.0 –0.5 Median 25%-75% Min-Max igure 3 Box-plot showing the median and interquartile ange for the gastric volume/weight ratio (vol/wt) in the three easurement times (p > 0.05). At all times, it is observed that here are volunteers with vol/wt ratio > 1.5 mL kg−1. 3 e r m v f m e o t h g f n f H t o t a c c o w c a n a u r A i t o t t a r t f s l a i f a b 5 a i p a a f f i t t u f d s o t e i b 2 t f v f u f s s a u e q u w ( fi G p a s o a v i s o e a t c o t l a s q c g t 9 d a T a m o c a t 80 valuate patients’ gastric content and volume and thus the isk of aspiration at bedside, in addition to help decision aking for anesthetic and airway management. It has been alidated15 and also considered highly reproducible.20 Aspiration of gastric contents is one of the most eared anesthetic complications and is still considered a ajor cause of morbidity and mortality related to gen- ral anesthesia.20 Described almost 70 years ago in one f the most widely cited articles of the medical litera- ure, Mendelson,21,22 who described aspiration in obstetrics, elped in the formation of anesthetic management through enerations. And ‘‘nothing by mouth’’ (NPO), empirically, or longer than 8---12 h has become a standard practice in the ame of security. The reason why such long periods of liquid asting were introduced into clinical practice is uncertain. owever, at a time in which pulmonary aspiration was one of he main causes of anesthetic mortality, the extrapolation f results of studies with rhesus monkeys to women arbi- rarily defined as at risk for aspiration those who presented gastric volume above 25 mL (0.4 mL kg−1) and pH < 2.5; the oncept of critical volume and pH was introduced.23 That laim later found support in another experiment carried ut on rhesus monkeys in which acid solution (0.4 mL kg−1) ith pH = 1.26 was instilled into the animal bronchi via tra- heotomy, resulting in cardiac arrest.19 Further studies,24,25 lso with monkeys, have shown that higher volumes were eeded to result in severe pneumonitis and death and, gain, extrapolation to humans increased the critical vol- me from 25 mL to 50 mL (0.8 mL kg−1), which significantly educed the number of patients considered ‘‘at risk’’. lthough this volume is probably considered insufficient by tself to lead to pulmonary aspiration, the combination of his critical volume with other factors, such as hiatal hernia r inadequate anesthesia, may be enough to cause aspira- ion with lung injury.26 Until then patients were subjected o prolonged fasting periods. And for about 20 years, the pproaches related to preoperative fasting began to be eviewed.7 Thus, current guidelines9,10 recommend clear liquids up o 2 h before surgery, which is a compromise between com- ort, cooperation and hydration, on the one hand, and ecurity on the other. And our results of quantitative ana- yzes supported exactly these guidelines, showing that 2 h fter clear fluid intake there was no significant changes n gastric contents compared to fasting over 8 h. Another requent question of all professionals working with surgery nd fast recommendation concerns the volume that can e ingested. Our study found that ingestion of 200 mL or 00 mL showed no difference in gastric residual volume fter a period of 2 h fasting, compared to overnight fast- ng. Although fluid intake is qualitatively associated with the resence of gastric fluid content, the volume was increased fter the ingestion of 500 mL. The stomach has many complex functions. It serves as reservoir for everything we eat, efficiently macerates ood, starts the early stages of digestion and then care- ully and slowly, almost methodically, releases its contents nto the small intestine. Solids follow a zero-order emp- ying kinetics. That is, at a constant speed according to he number of calories (about 200 kcal h−1).27---29 Clear liq- ids follow a dramatically different path, emptying quickly rom the stomach, following a first order kinetics27 (i.e., a c a c s F.M. Bisinotto et al. ecline described by an exponential curve). Some liquids uch as water and 0.9% saline have a very short half-life f about 10 min, and effectively only have a flush through he stomach.27,30 However, high-calorie liquids have a slower mptying rate, such as solid foods. In this study we used an sotonic energy value of 36 kcal per 200 mL. Thus, the num- er of calories ingested was 36 kcal by subjects who received 00 mL and 90 kcal by those who received 500 mL. All were at he same temperature and there was no rest after ingestion, actors that could alter gastric emptying. Because the same olunteers were tested in the three time points, individual actors did not influence the results obtained. Thus, the vol- me and the energy value of the ingested solution were the actors that influenced the results. Although there was no ignificant quantitative difference in the results obtained by tatistical comparison of the measurement times, there was n increase in the number of volunteers with gastric vol- me Grade 2 in the qualitative evaluation after 200 mL and, specially, after 500 mL compared with 8 h fasting. In this ualitative evaluation, the presence of some amount of liq- id inside the stomach should be considered even in patients ho fasted for more than 8 h. In this study, five volunteers 6.25%) (Fig. 3) had volumes greater than 1.5 mL kg−1 in the rst evaluation and four of them (5%) were classified as rade 2. These volumes are considered common in fasting atients, and considered safe.15 Oral and gastric secretions re constantly added to the stomach, which always contains ome amount of liquid. Saliva production occurs at a rate f 0.4---1.0 mL kg h−1, with endogenous gastric secretion in similar production rate.31 This explains the presence of arying amounts of liquid shown by ultrasonography in fast- ng volunteers, which were also seen after 2 h of isotonic olution ingestion, irrespective of the volume. Although there are numerous studies on the safety f drinking clear liquids up to 2 h before surgery and stablishment of preoperative fasting guidelines, many nesthesiologists and surgeons are still unsure of the prac- ice. Therefore, noninvasive assessments at the bedside that ould determine the volume of gastric contents in the peri- perative period would be of interest to assist in assessing he risk of pulmonary aspiration. Until recently there was a ack of a non-invasive diagnostic method that could promptly ssess gastric content and be applied perioperative. Ultra- ound is the first non-invasive technique that provides both uantitative and qualitative validated information of gastric ontents at bedside.12---15 Several studies suggest that the astric antrum is the stomach region that is more amenable o ultrasound examination.13,17,32 It can be identified in 8---100% of cases.14,16,33 Several mathematical models were eveloped for gastric volume calculation using the gastric ntrum image and calculating its cross-sectional area.14---16 his method can predict volumes of 0---500 mL and applies to dult patients with body mass index under 40 kg cm−2. The argin of error in measurements is only ±6 mL.15 There are ther methods to assess gastric emptying, but are not appli- able to the perioperative period.34,35 Gamma scintigraphy is noninvasive method considered a gold standard.35,36 It has he drawbacks of cost, use of radiation, and is not a practi- al exam. Ultrasonography is a very interesting technique. In ddition to measuring the gastric antrum, which allows the alculation of gastric volume through the formula used, a imple graduation of 0---2 may also be used for content eval- ion o 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 Use of ultrasound for gastric volume evaluation after ingest uation. Perlas et al.,13 in a study that evaluated the gastric volume in fasting patients, found 3.5% of subjects examined with the stomach classified as Grade 2, while in the present study we found 5%. The portability and convenience of these devices, combined with the low cost, allow its use at bedside and various types of diagnostic approaches, such as gastric evaluation. After years of uncertainty, studies have shown sufficient evidence of its accuracy and reproducibility. Although it has some limitations, as with all ultrasound techniques, which is dependent on the equipment quality and also the operator, the antrum is not identifiable in all patients and several steps need to be performed system- atically to obtain reliable results, besides not having the ability to evaluate the pH. The present study was conducted with healthy volunteers and, thus, the results may not be extrapolated to patients with chronic diseases or taken med- ications that alter the digestive system motility. For such patients, the fasting recommendations should be tailored. We conclude that in fasting healthy volunteers after receiving 200 mL or 500 mL of isotonic solution and remain- ing 2 h fasting, the gastric antral area, stomach expected volume, and gastric volume/weight show no significant dif- ferences compared to the same data after a minimum fasting period of 8 h in the sonographic evaluation. However, qual- itatively, there is an increase in the percentage of subjects with detectable liquid contents in both supine and right lat- eral decubitus positions 2 h after ingesting both 200 mL and especially 500 mL compared to fasting. Conflicts of interest The authors declare no conflicts of interest. Acknowledgements Gilberto Araújo Pereira, Professor of Biostatistics of the Nursing Course of UFTM. References 1. Ng A, Smith G. Gastroesophageal reflux and aspiration of gastric contents in anesthetic practice. Anesth Analg. 2001;93:494---513. 2. Neelakanta G, Chikyarappa A. 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http://refhub.elsevier.com/S0104-0014(17)30019-2/sbref0360 http://refhub.elsevier.com/S0104-0014(17)30019-2/sbref0360 http://refhub.elsevier.com/S0104-0014(17)30019-2/sbref0360 http://refhub.elsevier.com/S0104-0014(17)30019-2/sbref0360 http://refhub.elsevier.com/S0104-0014(17)30019-2/sbref0360 http://refhub.elsevier.com/S0104-0014(17)30019-2/sbref0360 http://refhub.elsevier.com/S0104-0014(17)30019-2/sbref0360 Use of ultrasound for gastric volume evaluation after ingestion of different volumes of isotonic solution Introduction Method Results Discussion Conflicts of interest Acknowledgements References