ISSN: 1676-4285

Fasting time and metabolic changes in elective surgeries: an integrative review Tempo de jejum e alterações metabólicas em cirurgias eletivas: revisão integrativa Tiempo de ayuno y cambios metabólicos en cirugías electivas: revisión integradora

Hadassa da Silva Caldeira de ABSTRACT Objective: To identify in the scientific production the occurrence of metabolic Moraes¹ changes in the postoperative period of elective surgeries and their relation with ORCID: 0000-0001-9812-835X preoperative fasting time. Method: An integrative review carried out from June to Cintia Silva Fassarella¹ July 2020 in the LILACS, MEDLINE, CINAHL, COCHRANE, SCOPUS, and EMBASE databases. Articles from 2015 to 2020 were selected. For the analysis of the ORCID: 0000-0002-2946-7312 evidence levels, the Oxford Centre for Evidence-Based Medicine categorization was Flavia Giron Camerini¹ followed. Results: A total of 10 scientific articles were selected. The metabolic ORCID: 0000-0002-4330-953X changes found were hyperglycemia, elevated serum levels of IL-6, cortisol, and valine, increased insulin resistance, decreased glutamic acid plasma levels, and Ricardo de Oliveira Meneses¹ increased IGF-1 levels with a reduction of IGFBP-3. Shortening the fasting time ORCID: 0000-0001-9962-2827 minimizes the patient's organic stress, with a reduction of metabolic changes, hospitalization time and morbidity. Conclusion: Preoperative fasting time longer Priscila Sanchez Bosco¹ than eight hours is related to metabolic changes in the postoperative period. Major ORCID: 0000-0001-8583-9371 surgeries present the greatest metabolic changes. KEYWORDS: Fasting; Metabolism; Elective Surgical Procedures; Patients. 1 State University of Rio de Janeiro RESUMO Objetivo: Identificar na produção científica a ocorrência de alterações metabólicas Editor: Paula Vanessa Peclat Flores no pós-operatório de cirurgias eletivas e sua relação com o tempo de jejum no pré- ORCID:0000-0002-9726-5229 operatório. Método: Revisão integrativa, realizada de junho a julho de 2020 nas bases de dados LILACS, MEDLINE, CINAHL, COCHRANE, SCOPUS e EMBASE. Foram selecionados artigos de 2015 a 2020. Para a análise dos níveis de evidência seguiu- Submission: 12/20/2020 se a categorização de Oxford Centre for Evidence-Based Medicine. Resultados: Approved: 03/18/2021 Foram selecionados 10 artigos científicos. As alterações metabólicas encontradas foram hiperglicemia, elevação dos níveis séricos de IL-6, cortisol e valina, aumento da resistência insulínica, queda dos níveis plasmáticos de ácido glutâmico e elevação dos níveis de IGF-1 com a redução de IGFBP-3. A abreviação do tempo de jejum minimiza o estresse orgânico ao paciente, com a redução das alterações metabólicas, tempo de internação e morbidade. Conclusão: O tempo de jejum pré-operatório superior a oito horas está relacionado a ocorrência de alterações metabólicas no pós-operatório. As cirurgias de grande porte apresentam as maiores alterações metabólicas. DESCRITORES: Jejum; Metabolismo; Procedimentos Cirúrgicos Eletivos; Pacientes.

RESUMEN Objetivo: Identificar en la producción científica la existencia de cambios metabólicos en el postoperatorio de cirugías electivas y su relación con el tiempo de ayuno en el período preoperatorio. Método: Revisión integradora, realizada de junio a julio de 2020 de las bases de datos LILACS, MEDLINE, CINAHL, COCHRANE, SCOPUS y EMBASE. Se seleccionaron artículos de 2015 a 2020. Para el análisis de los niveles de evidencia se siguió la categorización del Oxford Center for Evidence- Based Medicine. Resultados: Se seleccionaron 10 artículos científicos. Las alteraciones metabólicas encontradas fueron hiperglucemia, niveles séricos elevados de IL-6, cortisol y valina, aumento de la resistencia a la insulina, reducción de los niveles plasmáticos de ácido glutámico y aumento de los niveles de IGF-1 con disminución de IGFBP-3. La disminución del tiempo de ayuno minimiza el estrés orgánico del paciente, con una reducción de los cambios metabólicos, la duración de la estancia hospitalaria y la morbilidad. Conclusión: Existe una relación entre un tiempo de ayuno preoperatorio mayor a ocho horas y la presencia de cambios metabólicos en el postoperatorio. Las cirugías mayores muestran los mayores cambios metabólicos. DESCRIPTORES: Ayuno; Metabolismo; Procedimientos Quirúrgicos Electivos; Pacientes.

Moraes HSC, Fassarella CS, Camerini FG, Meneses RO, Bosco PS. Fasting time and metabolic changes in elective surgeries: an integrative review. Online Braz J Nurs [Internet]. 2020 [cited year month day]; 20:e20216480. Available from: https://doi.org/10.17665/1676-4285.20216480 INTRODUCTION carbohydrate-rich solutions in the

Preoperative fasting, required for carrying out preoperative period(2). surgical procedures, has been widely In Brazil, the Accelerated Total Postoperative discussed in the last few years. In general, the Recovery (Aceleração da Recuperação Total traditional fasting practice corresponds to a Pós-Operatória, ACERTO) project was period between eight and twelve hours of instituted. Created in 2005, the project complete liquid and food restriction, and it can suggests offering a maltodextrin solution up to exceed twelve hours due to delays in the two hours before the surgical procedure(3). surgical schedule, cancellation of surgeries, or Guidelines such as those set up by the other factors(1). European Society of Anaesthesiology (ESA)

An extended preoperative fasting period can recommend solid food restriction to start promote sensations of thirst, anxiety and between six and eight hours before anesthetic headache, which can negatively interfere with induction(4). the postoperative period. In addition to that, Shortening fasting time by the extended fasting leads to metabolic stress intake/administration of a carbohydrate-rich triggered by the surgical trauma, generating solution up to two hours before the surgery, an increase in insulin resistance and the as well as early feeding in the postoperative occurrence of catabolic reactions in the period, provides the patient with greater organism, culminating in a longer comfort and can optimize the reestablishment hospitalization period and higher levels of of the physiological functions, promoting a postoperative complications(1). rapid restoration of the bowel functions, better

Currently, new multi-professional and glycemic control, and a reduction of surgical institutional protocols and guidelines have site infections in the postoperative period. indicated the reduction of the traditional However, the implementation of protocols fasting practice as a strategy to accelerate aimed at this behavior still faces resistance in postoperative recovery, based on the the assistance practice(2). principles of the evidence-based practice(2). In This research is justified as it supports the

2001, the Enhanced Recovery After systematization and redirection of safe and

Surgery (ERAS), a European program on quality assistance, as well as it leads the postoperative care, established a safe protocol design of protocols aimed at patient safety with preoperative measures to optimize the and at the consolidation of new preoperative nutritional aspects and implement conducts, consequently improving the quality

of the assistance provided to the surgical

patient. Thus, this study has as its objective to filters, “articles published in English, Spanish identify in the scientific production the or Portuguese, produced in the last five years occurrence of metabolic changes in the (2015-2020)” were used, seeking the most postoperative period of elective surgeries and updated evidence on the theme. Articles with their relation with the fasting time in the no clear method outlining, theses and preoperative period. dissertations, and articles not available in full

for consultation were excluded, as well as

METHOD protocols, Guidelines, and secondary-source

This is an integrative review. Six stages were studies. In the case of duplicate articles, only followed(5) to elaborate this study. To guide one copy was used. the formulation of the research question, The eligibility criteria were applied in the carried out in the first stage of the study, the abstracts. The selection of the articles was

PICo strategy was used, a methodology initially carried out by a previous reading of employed to elaborate the question for the abstract, in order to verify its relation with evidence search in the literature, intended to the topic, so that full reading could be non-clinical studies, as it is the case of this initiated. The search was carried out in the study. Thus, the research question was following databases: Latin American and structured in three elements(6): P (Patients); I Caribbean Literature in Health

(Fasting) and (Metabolism); Co (Elective Sciences (Literatura Latino-Americano e do

Surgical Procedures). The following question Caribe em Ciências da Saúde, LILACS) via the was considered as the study question: “What Virtual Health Library (Biblioteca Virtual em are the metabolic changes that occur in the Saúde, BVS), International Literature in Health postoperative period of elective surgeries and Sciences (MEDLINE) via PUBMED, SciVerse their relation with the preoperative fasting Scopus (SCOPUS), Cumulative Index to time?” Nursing and Allied Health Literature (CINAHL)

In the second stage, the following inclusion via CAFe, Cochrane Library (COCHRANE) via criteria were determined: studies in adults CAFe, and Excerpta Medica over 18 years old, which address the issue of Database (EMBASE) via CAFe. metabolic changes related to extended The following DeCS/MESH/Emtree thesaurus preoperative fasting in elective surgeries; were used for the study: methodological-based studies of experimental Pacientes/Patients/Patient, Jejum/Fasting, or quasi-experimental design; and time-series Metabolismo/Metabolism and Procedimentos or control cases, indexed in the databases. As cirúrgicos eletivos/Elective Surgical

Procedures/Elective Surgery. The definition of In the fourth stage, the selected texts were controlled descriptors was referenced under read and interpreted by completing an the Health Sciences Descriptors in Health instrument previously elaborated by the

Sciences (Descritores em Ciências da author to obtain the information needed to

Saúde, DeCS) and Medical Subject analyze the metabolic changes in the

Headings (MESH) terms. postoperative period of patients subjected to

Due to the specific features of each database, extended preoperative fasting. For each the search strategies were adapted according primary study included, a synthesis chart was to the objective and inclusion criteria of this elaborated containing the following study. The search for the articles took place information: author(s), year of publication, from June to July 2020. type of study, level of evidence, objective(s)

Initially, isolated descriptors were used to and main results. search for the articles with the aid of the To reduce the number of interpretation errors

Boolean operator OR; however, a high number of the results and outlining of the analyzed was obtained for the objective of this study. studies (bias), the search was carried

To enhance the search, the Boolean operator independently by evaluators in the same

AND was included, in addition to OR, along databases and with the same descriptors, in with the association of four descriptors. the end presenting 100% agreement in the

In the third stage, the full texts were findings. In addition to that, two reviewers evaluated by two reviewers regarding their verified the validation of the methodological methodological validity. The studies were quality in an independent manner. There was classified in relation to the evidence level, no disagreement between them. according to the Oxford Centre for Evidence-

Based Medicine(7) categorization, classified as RESULTS

1A (systematic review), 1B (randomized A total of 10 articles that met the inclusion clinical trial), 2A (systematic review of cohort criteria previously established were analyzed studies), 2B (cohort study and randomized for this integrative review. The selection clinical trial of lower quality), 2C (research process of the articles was described through results), 3A (systematic review of case-control a flowchart, as recommended in the Preferred study), 3B (case-control study), 4 (case Reporting Items for Systematic reviews and report), and 5 (specialist opinion and non- Meta-Analyses (PRISMA)(8), which can be seen systematic review). in Figure 1.

Figure 1: PRISMA flowchart (adapted) to the study selection and inclusion process. Rio de Janeiro, RJ, Brazil,

2020.

Regarding the databases, four articles (40%) 2019. Among the articles analyzed, only one were identified in PubMed and two (20%) (10%) was developed in Brazil. The others were simultaneously found in EMBASE, correspond to international publication

Scopus, and the BVS. As for the year of articles, as shown in Figure 2, with the publication, 40% (four articles) date from features of the selected studies.

Figure 2: Summary of the selected articles. Rio de Janeiro, RJ, Brazil, 2020. Author/Year/Country Type of Evidence Objective Main findings study Level (Oxford Centre for Evidence- Based Medicine) Pędziwiatr M, Pisarska Randomized 1B To establish the The study analyzed 40 M, Matłok M, Major P, clinical trial influence of the patients. Hyperglycemia Kisielewski M, Wierdak preoperative intake and an increase in the M, et al.(9) of a carbohydrate- cortisol levels were 2015 rich solution on the found in the immediate Poland insulin resistance postoperative period,

and cortisol levels in with a decrease within patients subjected 24 hours. The most to elective expressive changes laparoscopic were found in the cholecystectomy. patients with longer fasting time (> 8 hours). Bang P, Thorell A, Case-control 3B To investigate the 18 patients were Carlsson-Skwirut C, study hypothesis that analyzed. The oral Ljungqvist O, Brismar shortened fasting carbohydrate solution K, Nygren J.(10) promotes ingested by the patients 2016 proteolysis of serum in the 2 hours prior to Sweden IGFBP-3-PA the surgery promoted (Insulin-like growth an 18% improvement in factor binding insulin sensibility, protein -3), greater IGFBP-3 increases the proteolysis, and greater bioavailability of bioavailability of the circulating IGF-I circulating IGF-I in the (insulin-like growth postoperative period. factor), and The patients subjected preserves insulin to extended sensibility when preoperative fasting compared to the presented greater effects of extended postoperative insulin fasting on elective resistance. colorectal surgery. Dilmen OK, Yenturb E, Case-control 1B To evaluate the The study evaluated 43 Tunalia Y, Balcic H, study metabolic effects of ASA I-II patients. Bahar M.(11) shortened fasting Groups of patients in 2017 by the intake of a extended and shortened Turkey preoperative preoperative fasting carbohydrate were compared. The solution in lumbar was an increase in the disc surgery. cortisol and IL-6 levels in the postoperative period both in patients in extended fasting and in those in shortened fasting, with no significant difference. The study found that, regardless of the fasting time, insulin resistance was present in the postoperative period of lumbar disc surgeries. Kreutzenberg S, Vigili Prospective 2B To identify the A total of 38 patients D, Avogaro A.(12) cohort study serum levels of (16 with diabetes and 2017 3BOHB in patients 22 without diabetes) Italy with and without were recruited for the type 2 diabetes study. A positive (DM2), before and correlation was after an elective detected between coronary fasting time and fasting angiography; to plasma glucose levels detect the changes (the longer the fasting

in the 3BOHB levels time, the greater the during the postoperative procedure and to hyperglycemia perform possible condition). On the other associations hand, there was no between 3BOHB association between and the clinical fasting time and 3BOHB parameters/results levels. obtained. Burstal RJ, Reilly JR, Prospective 2B To investigate In total, 100 patients Burstal B.(13) cohort study ketonemia and the were evaluated. No 2018 relation between relation was observed Australia beta- between fasting time hydroxybutyrate, and the ketone or glycemia, and glucose levels. preoperative fasting Hyperketonemia was in non-diabetic identified in three of the adults subjected to 100 patients, one of extended fasting for whom ingested a elective or ketogenic supplement emergency the night before the surgeries. surgery. No patient in extended fasting showed beta- hydroxybutyrate levels suggestive of ketoacidosis. Hosny H, Desa MI, El- Case-control 2B To compare the The study was carried Siory W, Abdel-Monem study metabolic effects of out with 63 patients. A. (14) shortened fasting The most expressive 2018 by means of a metabolic changes were London preoperative found in patients in infusion of a lipid or extended fasting. The carbohydrate FFA, insulin, glucose, emulsion to the triglycerides, and VLDL conventional levels were significantly preoperative fasting lower in the group (> 8 hours) on the subjected to the shorter postoperative fasting time and that insulin and free received the fatty acid (FFA) preoperative lipid levels in obese infusion. patients subjected to myocardial revascularization. Reis PGA, Polakowski C, Case-control 2B To evaluate the 33 patients were Lopes M, Bussyguin DS, study influence of included (15 in Ferreira RP, Preti VB. shortened shortened fasting and (15) preoperative fasting 18 in conventional 2019 on the outcomes of fasting). Shorter time to Brazil patients subjected fully reach full feeding to colorectal cancer was required in patients surgery. in shortened fasting when compared to those in extended fasting (10 versus 16 days), noting that the

shorter the fasting time, the better the nutritional metabolic recovery in postoperative patients.

Yeniay O, Tekgul ZT, Prospective 2B To measure the 211 patients were Okur O, Koroglu N. (16) observational preoperative fasting investigated. The mean 2019 study time comparing it to fasting times were Turkey the period of the 12 ± 2.8 and day in which the 95 ± 2.1 hours in the procedure was morning group, and carried out 15.5 ± 3.4 and (morning, 12.7 ± 4.4 in the afternoon, and afternoon group for night), and to food and liquid, evaluate the effect respectively. ECG of fasting on the changes were vital parameters significantly more and frequent in the group electrocardiogram with longer in aged patients preoperative fasting subjected to time. elective surgery under spinal anesthesia. Wuensch T, Quint J, Prospective 2B To investigate 50 patients were Mueller V, Mueller A, observational plasma markers investigated. The Wizenty J, Kaffarnik M, study. sensible to the patients with et al.(17) preoperative fasting preoperative fasting 2019 time that allow for time over 16 hours Germany the metabolic presented an increase characterization of in the plasma levels of surgical patients for valine, leucine, serine, a preoperative a-amino butyric acid, metabolic free fatty acids, and 3- preparation hydroxy butyric acid. optimized in Only valine and patients subjected glutamic acid appear as to gastrointestinal independent metabolic tract elective markers for a precise surgery. prediction of changes related to extended fasting (in this case, more than or equal to 20 hours) Liu B, Wang Y, Liu S, Randomized 1B To compare the The study evaluated Zhao T, Zhao B, Jiang clinical trial metabolic effects 120 patients. The X, et al.(18) induced by the patients with longer 2019 shortened preoperative fasting China preoperative time presented an fasting, with increase in the glycemic ingestion of an oral levels and greater carbohydrate insulin resistance when solution two hours compared to those with

before the surgical shorter fasting time. procedure and the Better glucose extended homeostasis was preoperative fasting achieved in patients lasting more than who ingested the oral eight hours in carbohydrate solution elective craniotomy. during the preoperative period. Source: Authors, 2020. IGFBP-3: Type 3 IGF-I binding protein; IGF-I: type 1 insulin-like growth factor; FFA: free fatty acid; VLDL: very low-density lipoprotein; 3BOHB: 3-hydroxybutyrate.

Eight studies (80%) found metabolic changes The results of the studies show the relation when evaluating the influence of shortened between the preoperative fasting time and the fasting, comparing groups in conventional metabolic changes observed in the preoperative fasting (8 to 12 hours) to groups postoperative period, when the metabolic subjected to shortened fasting time upon markers involved in the organic processes of ingestion of a carbohydrate solution within two response to surgical trauma oscillate, hours before the surgical procedure, according enhanced by the catabolic reactions promoted to what is proposed by programs for the by the extended fasting time. The main clinical optimization of postoperative recovery(9-15,18), markers investigated and the respective while the other studies investigated the metabolic changes found in the studies are metabolic changes only in patients with described in Figure 3. extended fasting time, with no comparative analysis(16,17).

Figure 3: Metabolic changes and the relation with preoperative fasting time. Rio de Janeiro, RJ, Brazil, 2020. Metabolic Fasting Main changes Marker time Glucose ≥ 8 hours (1) Progressive increase in serum glucose level from intraoperative to the first three hours after elective craniotomy. (2) Progressive increase in the glucose level from the immediate postoperative period, decreasing 24 hours after laparoscopic cholecystectomy. Plasma ≥ 8 hours (1) Increase in the insulin level during the intraoperative period, insulin decreasing progressively from 2 hours post-procedure, returning to the baseline levels three hours after the craniotomy. (2) Progressive increase in the insulin level from the immediate postoperative period up to 24 hours after the laparoscopic cholecystectomy. Cortisol ≥ 8 hours (1) Increase in the cortisol plasma levels two hours after the skin incision in lumbar discectomy. (2) Increase in plasma cortisol immediately after the laparoscopic

cholecystectomy, with an expressive decrease 24 hours after procedure conclusion. IGF-I ≥ 8 hours A significant decrease in IGF-I and in the IGFBP-3 proteolysis, with a IGFBP-3-PA consequent increase in postoperative insulin resistance in patients subjected to abdominal surgery.

Valine ≥ 16-20 Increase in the postoperative valine plasma concentration in patients hours subjected to gastrointestinal tract surgery. Glutamic ≥ 16-20 Reduction in glutamic acid plasma levels in patients subjected to Acid hours gastrointestinal tract surgery.

Interleukin 6 ≥ 8 hours Increase in the IL-6 levels in the lumbar discectomy immediate (IL-6) postoperative period. Source: Authors, 2020.

DISCUSSION cholecystectomy. No significant differences

From the analysis of the selected articles, the were found between the groups, a results found were stratified into two postoperative glycemic increase being found in categories according to the study objective. both, with values between

129.67 ± 18.6 mg/dL in the traditional fasting

1. Metabolic changes in the postoperative group (>8 hours) and 124.34 ± 20.62 mg/dL period of elective surgeries: in the shortened fasting group(19).

In the analysis of the primary results of the In major procedures such as non-laparoscopic studies, glucose and insulin oscillated gynecological surgeries, the glycemic increase similarly, with an increase in the serum levels was more expressive. In Brazil, a study at the immediate postoperative period and a identified a 55.19% increase in the progressive drop in the first 24 hours in postoperative glycemic level of patients in patients subjected to extended preoperative extended fasting, whereas in the shortened fasting(9,18). fasting group the glycemic increase was

When comparing the effects of conventional 32.53%, showing that shortening the fasting to shortened fasting in the preoperative fasting time reduces the organic preoperative period of laparoscopic answer to the trauma(20). cholecystectomy, one study observed glucose In fact, the metabolic changes provoked by and insulin increases in both; however, with extended preoperative fasting are proportional no influence of the preoperative fasting time to the magnitude of the surgery, being more on the metabolic condition of the patients expressive in major surgical procedures(21). during and after the procedure(9). In addition to changes in the postoperative

Similar results were found in another study glycemic levels, alterations in the secretion of with patients subjected to laparoscopic the cortisol hormone are identified. Among the

analyzed studies, two verified a significant carbohydrates on insulin resistance and on the increase in the cortisol serum levels in the response to surgical stress after lumbar immediate postoperative period of major and discectomy, using interleukin-6 as marker, medium-size surgeries(9,11). verifying that the IL-6 plasma levels increased

In the clinical practice, high cortisol levels in considerably after 24 hours of skin incision in surgical patients can influence the the group subjected to conventional postoperative insulin resistance levels and fasting(11). glycemic changes(22). The increase of the A European research study, upon evaluation of cortisol secretion arises from the neuro- the IL-6 levels in 137 patients in the pre- and endocrine response produced by the organism postoperative periods, verified a high level of after the surgical trauma, which corroborates IL-6 (≥ 432 pg/mL), as well as a 3 times the results found. They excessively stimulate higher risk of postoperative complications and the catabolic state that contributes to an increase in hospitalization time. Outcomes perioperative hyperglycemia and severe such as pneumonia, sepsis, anastomotic complications, such as diabetic ketoacidosis, dehiscence, wound infection, mortality, and or a non-ketotic hyperglycemic hyperosmolar re-surgery were found(25). state(23). Changes in the IGF-1 (insulin-like growth

Insulin resistance develops during the surgery factor) and IGFBP-3 (IGF-1 binding protein 3) and is present for a long time in the serum levels were also detected among postoperative period(23). It can last up to three patients with preoperative fasting times longer weeks after the performance of elective than eight hours. In the postoperative period surgeries, with greater intensity on the first of abdominal surgeries, 18 patients had a and second day of the postoperative period(24). significant reduction in the IGF-I levels and in

Another biomarker with possible relevance in IGFBP-3 proteolysis, with a consequent the metabolic state of surgical patients is increase in insulin resistance(10). interleukin-6 (IL-6), a pro-inflammatory In contrast, patients in shortened fasting had cytokine that mediates the immune response an increase in IGF-I and in IGFBP-3 and acts on several cell types. It presents a proteolysis, that is, lower circulating levels of positive correlation with insulin resistance and free IGFBP-3 in plasma, indicating that the is found at high levels in chronic diseases like increased availability of IGF-I and the effects

DM2(23). of IGF-I on glucose uptake are involved in the

One of the selected articles evaluated the hormone mechanisms for a lower insulin effect of the ingestion of preoperative oral resistance after the surgical trauma(10).

Another study identified a reduction in the protein to provide the hepatic gluconeogenesis

IGFB-3 circulating levels by analyzing 80 with substrates throughout the fasting period, patients subjected to mastectomy with since valine oxidation is increased in times of reduced fasting time and who received a inadequate supply of amino acids(17). carbohydrate solution two hours before the No recent reports were found in the literature surgery(26). Despite these findings, there is a on the influence of valine and glutamic acid on scarcity of updated studies addressing the the postoperative period and its relation with effects of extended preoperative fasting on the fasting time. Considering the results obtained

IGF-1 and IGBP-3 levels and the by the analyzed study(17). The publication of consequences of these changes in the new studies that investigate the influence of postoperative outcome in different medical preoperative fasting time on the valine and specialties. the glutamic acid levels, as well as the

Metabolic effects of extended fasting on the metabolic impact on the postoperative valine and glutamic acid levels were reported recovery, becomes relevant. in one of the studies included in this review, in which 50 patients in preoperative fasting for 2. Relation of the postoperative metabolic more than 16 hours, subjected to changes with preoperative fasting time: gastrointestinal surgery, presented an Extended preoperative fasting enhances the expressive increase in the plasma metabolic response to the surgical trauma(4). concentration of valine and a reduction in the The American Society of postoperative glutamic acid levels(17). Anesthesiologists (ASA) recommends the

A possible mechanism that causes the decline conducts established by the ERAS and in glutamic acid throughout extended fasting ACERTO multimodal protocols, anticipating is the hepatic catabolism of glutamic acid, fasting by ingesting clear liquids up to two intensified in this condition by an increase in hours and light meals up to six hours for the activity of glutamate dehydrogenase, an healthy patients before elective surgical important enzyme in the hepatic regulation of procedures that need general/local anesthesia nitrogen and energy metabolism, catalyzing or sedation/analgesia(28). one of the most relevant anaplerotic The ten articles reviewed addressed fasting reactions(27). time in their studies, in which six used the

In contrast, the valine levels increased as case-control method to compare which results fasting time advanced, which can be explained were more beneficial to the patient(9-14). These by an increase in the degradation of muscle are studies coming from different nations,

which demonstrates that the shortening of of the preoperative fasting time obtained for preoperative fasting is still little practiced, minor surgeries was 15 hours, while for even with the advent of studies that prove its medium-complexity surgeries was 13.5 hours, effectiveness. which demonstrates non-conformity with the

In the case-control studies that compared new guidelines. The study also found that patients in traditional fasting (more than 8 malnourished patients presented longer pre- hours) to patients in shortened fasting (six and postoperative fasting and hospitalization hours for solids and two hours for liquids), it time when compared to those well- was possible to note that the fasting time nourished(31). reflects the reality of many hospital In Argentina, the fasting time established by institutions, where the relation between time institutions also surpasses the and the fasting prescribed and practiced is recommendations of the current guidelines. In disproportionate(29). In these articles, it was a study with 139 patients, the mean of the evidenced that fasting with a mean of two preoperative fasting time prescribed was 12.5 hours for clear fluids, including carbohydrate- hours, both for solids and liquids, while the rich beverages, reduced the postoperative actual fasting had a mean of 14 hours for solid metabolic changes(9-14). food, being longer than prescribed. In

In fact, the reduction in fasting time promotes comparison to the recommendation of the a safer and more beneficial postoperative AAARBA (Asociación de Anestesia, Analgesia y period to the patients. When observing the Reanimación de Buenos Aires) guidelines, implementation of the ERAS protocols to prescribed fasting exceeded the 4.5-hour hepatic surgery in a Brazilian tertiary care recommendation for solids and 10.5 for center, in the group of patients subjected to liquids, not fitting into the current

ERAS, a reduction in preoperative fasting time recommendations(32). was observed (six hours for solids and two One of the articles selected, published in hours for liquids) and, consequently, a two- Germany, reports the length of preoperative day reduction in the postoperative fasting for a mean time that varied between hospitalization time(30). 16 and 20 hours(16). Another study from

The fasting time recommended by the studies Turkey compared the time of the day in which was at least eight hours for food and liquid. In the surgery was carried out to the effect of

Brazil, when evaluating the clinical, surgical, fasting time on an elective surgery. The and nutritional profile of 140 surgical patients fasting means were 12 ± 2.8 and admitted in a reference hospital, the median 9.5 ± 2.1 hours in the morning group and

15.5 ± 3.4 and 12.7 ± 4.4 in the afternoon The results found in this study corroborate for group for solids and liquids, respectively. The a reformulation of the care practices for the greatest changes occurred in the group with surgical patient, by reducing preoperative longer fasting time(16). fasting time, providing the patient with

Therefore, preoperative fasting time has a greater comfort and well-being, reducing direct relation proportional to the occurrence sensations of thirst and hunger, in addition to of postoperative metabolic changes. a safer clinical/metabolic post-surgery

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