Fasting time and metabolic changes in elective surgeries: an integrative review

s. The selection of the articles was initially carried out by a previous reading of the abstract, in order to verify its relation with the topic, so that full reading could be initiated. The search was carried out in the following databases: Latin American and Caribbean Literature in Health Sciences (Literatura Latino-Americano e do Caribe em Ciências da Saúde, LILACS) via the Virtual Health Library (Biblioteca Virtual em Saúde, BVS), International Literature in Health Sciences (MEDLINE) via PUBMED, SciVerse Scopus (SCOPUS), Cumulative Index to Nursing and Allied Health Literature (CINAHL) via CAFe, Cochrane Library (COCHRANE) via CAFe, and Excerpta Medica Database (EMBASE) via CAFe. The following DeCS/MESH/Emtree thesaurus were used for the study: Pacientes/Patients/Patient, Jejum/Fasting, Metabolismo/Metabolism and Procedimentos cirúrgicos eletivos/Elective Surgical Procedures/Elective Surgery. The definition of controlled descriptors was referenced under the Health Sciences Descriptors in Health Sciences (Descritores em Ciências da Saúde, DeCS) and Medical Subject Headings (MESH) terms. Due to the specific features of each database, the search strategies were adapted according to the objective and inclusion criteria of this study. The search for the articles took place from June to July 2020. Initially, isolated descriptors were used to search for the articles with the aid of the Boolean operator OR; however, a high number was obtained for the objective of this study. To enhance the search, the Boolean operator AND was included, in addition to OR, along with the association of four descriptors. In the third stage, the full texts were evaluated by two reviewers regarding their methodological validity. The studies were classified in relation to the evidence level, according to the Oxford Centre for EvidenceBased Medicine categorization, classified as 1A (systematic review), 1B (randomized clinical trial), 2A (systematic review of cohort studies), 2B (cohort study and randomized clinical trial of lower quality), 2C (research results), 3A (systematic review of case-control study), 3B (case-control study), 4 (case report), and 5 (specialist opinion and nonsystematic review). In the fourth stage, the selected texts were read and interpreted by completing an instrument previously elaborated by the author to obtain the information needed to analyze the metabolic changes in the postoperative period of patients subjected to extended preoperative fasting. For each primary study included, a synthesis chart was elaborated containing the following information: author(s), year of publication, type of study, level of evidence, objective(s)