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

Hadassa da Silva Caldeira de Moraes1, Cintia Silva Fassarella1, Flavia Giron Camerini1, Ricardo de Oliveira Meneses1, Priscila Sanchez Bosco1

1 State University of Rio de Janeiro, RJ, Brazil

ABSTRACT

Objective: To identify in the scientific production the occurrence of metabolic changes in the postoperative period of elective surgeries and their relation with preoperative fasting time. Method: An integrative review carried out from June to July 2020 in the LILACS, MEDLINE, CINAHL, COCHRANE, SCOPUS, and EMBASE databases. Articles from 2015 to 2020 were selected. For the analysis of the evidence levels, the Oxford Centre for Evidence-Based Medicine categorization was followed. Results: A total of 10 scientific articles were selected. The metabolic changes found were hyperglycemia, elevated serum levels of IL-6, cortisol, and valine, increased insulin resistance, decreased glutamic acid plasma levels, and increased IGF-1 levels with a reduction of IGFBP-3. Shortening the fasting time minimizes the patient's organic stress, with a reduction of metabolic changes, hospitalization time and morbidity. Conclusion: Preoperative fasting time longer than eight hours is related to metabolic changes in the postoperative period. Major surgeries present the greatest metabolic changes.

Keywords: Fasting; Metabolism; Elective Surgical Procedures; Patients. 

INTRODUCTION

Preoperative fasting, required for carrying out surgical procedures, has been widely discussed in the last few years. In general, the traditional fasting practice corresponds to a period between eight and twelve hours of complete liquid and food restriction, and it can exceed twelve hours due to delays in the surgical schedule, cancellation of surgeries, or other factors(1).

An extended preoperative fasting period can promote sensations of thirst, anxiety and headache, which can negatively interfere with the postoperative period. In addition to that, extended fasting leads to metabolic stress triggered by the surgical trauma, generating an increase in insulin resistance and the occurrence of catabolic reactions in the organism, culminating in a longer hospitalization period and higher levels of postoperative complications(1).

Currently, new multi-professional and institutional protocols and guidelines have indicated the reduction of the traditional fasting practice as a strategy to accelerate postoperative recovery, based on the principles of the evidence-based practice(2). In 2001, the Enhanced Recovery After Surgery (ERAS), a European program on postoperative care, established a safe protocol with preoperative measures to optimize the nutritional aspects and implement carbohydrate-rich solutions in the preoperative period(2).

In Brazil, the Accelerated Total Postoperative Recovery (Aceleração da Recuperação Total Pós-Operatória, ACERTO) project was instituted. Created in 2005, the project suggests offering a maltodextrin solution up to two hours before the surgical procedure(3). Guidelines such as those set up by the European Society of Anaesthesiology (ESA) recommend solid food restriction to start between six and eight hours before anesthetic induction(4).

Shortening fasting time by the intake/administration of a carbohydrate-rich solution up to two hours before the surgery, as well as early feeding in the postoperative period, provides the patient with greater comfort and can optimize the reestablishment of the physiological functions, promoting a rapid restoration of the bowel functions, better glycemic control, and a reduction of surgical site infections in the postoperative period. However, the implementation of protocols aimed at this behavior still faces resistance in the assistance practice(2).

This research is justified as it supports the systematization and redirection of safe and quality assistance, as well as it leads the design of protocols aimed at patient safety and at the consolidation of new preoperative conducts, consequently improving the quality of the assistance provided to the surgical patient. Thus, this study has as its objective to identify in the scientific production the occurrence of metabolic changes in the postoperative period of elective surgeries and their relation with the fasting time in the preoperative period.

METHOD

This is an integrative review. Six stages were followed(5) to elaborate this study. To guide the formulation of the research question, carried out in the first stage of the study, the PICo strategy was used, a methodology employed to elaborate the question for evidence search in the literature, intended to non-clinical studies, as it is the case of this study. Thus, the research question was structured in three elements(6): P (Patients); I (Fasting) and (Metabolism); Co (Elective Surgical Procedures). The following question was considered as the study question: “What are the metabolic changes that occur in the postoperative period of elective surgeries and their relation with the preoperative fasting time?”

In the second stage, the following inclusion criteria were determined: studies in adults over 18 years old, which address the issue of metabolic changes related to extended preoperative fasting in elective surgeries; methodological-based studies of experimental or quasi-experimental design; and time-series or control cases, indexed in the databases. As filters, “articles published in English, Spanish or Portuguese, produced in the last five years (2015-2020)” were used, seeking the most updated evidence on the theme. Articles with no clear method outlining, theses and dissertations, and articles not available in full for consultation were excluded, as well as protocols, Guidelines, and secondary-source studies. In the case of duplicate articles, only one copy was used.

The eligibility criteria were applied in the abstracts. 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 Evidence-Based Medicine(7) 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 non-systematic 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) and main results.

To reduce the number of interpretation errors of the results and outlining of the analyzed studies (bias), the search was carried independently by evaluators in the same databases and with the same descriptors, in the end presenting 100% agreement in the findings. In addition to that, two reviewers verified the validation of the methodological quality in an independent manner. There was no disagreement between them.

RESULTS

A total of 10 articles that met the inclusion criteria previously established were analyzed for this integrative review. The selection process of the articles was described through a flowchart, as recommended in the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA)(8), which can be seen 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%) were identified in PubMed and two (20%) were simultaneously found in EMBASE, Scopus, and the BVS. As for the year of publication, 40% (four articles) date from 2019. Among the articles analyzed, only one (10%) was developed in Brazil. The others correspond to international publication articles, as shown in Figure 2, with the features of the selected studies.

Figure 2: Summary of the selected articles. Rio de Janeiro, RJ, Brazil, 2020.

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 when evaluating the influence of shortened fasting, comparing groups in conventional preoperative fasting (8 to 12 hours) to groups subjected to shortened fasting time upon ingestion of a carbohydrate solution within two hours before the surgical procedure, according to what is proposed by programs for the optimization of postoperative recovery(9-15,18), while the other studies investigated the metabolic changes only in patients with extended fasting time, with no comparative analysis(16,17).

The results of the studies show the relation between the preoperative fasting time and the metabolic changes observed in the postoperative period, when the metabolic markers involved in the organic processes of response to surgical trauma oscillate, enhanced by the catabolic reactions promoted by the extended fasting time. The main clinical markers investigated and the respective metabolic changes found in the studies are described in Figure 3.

Figure 3: Metabolic changes and the relation with preoperative fasting time. Rio de Janeiro, RJ, Brazil, 2020

Source: Authors, 2020.

DISCUSSION

From the analysis of the selected articles, the results found were stratified into two categories according to the study objective.

1. Metabolic changes in the postoperative period of elective surgeries:

In the analysis of the primary results of the studies, glucose and insulin oscillated similarly, with an increase in the serum levels at the immediate postoperative period and a progressive drop in the first 24 hours in patients subjected to extended preoperative fasting(9,18).

When comparing the effects of conventional fasting to shortened fasting in the preoperative period of laparoscopic cholecystectomy, one study observed glucose and insulin increases in both; however, with no influence of the preoperative fasting time on the metabolic condition of the patients during and after the procedure(9).

Similar results were found in another study with patients subjected to laparoscopic cholecystectomy. No significant differences were found between the groups, a postoperative glycemic increase being found in both, with values between 129.67 ± 18.6 mg/dL in the traditional fasting group (>8 hours) and 124.34 ± 20.62 mg/dL in the shortened fasting group(19).

In major procedures such as non-laparoscopic gynecological surgeries, the glycemic increase was more expressive. In Brazil, a study identified a 55.19% increase in the postoperative glycemic level of patients in extended fasting, whereas in the shortened fasting group the glycemic increase was 32.53%, showing that shortening the preoperative fasting time reduces the organic answer to the trauma(20).

In fact, the metabolic changes provoked by extended preoperative fasting are proportional to the magnitude of the surgery, being more expressive in major surgical procedures(21).

In addition to changes in the postoperative glycemic levels, alterations in the secretion of the cortisol hormone are identified. Among the analyzed studies, two verified a significant increase in the cortisol serum levels in the immediate postoperative period of major and medium-size surgeries(9,11).

In the clinical practice, high cortisol levels in surgical patients can influence the postoperative insulin resistance levels and glycemic changes(22). The increase of the cortisol secretion arises from the neuro-endocrine response produced by the organism after the surgical trauma, which corroborates the results found. They excessively stimulate the catabolic state that contributes to perioperative hyperglycemia and severe complications, such as diabetic ketoacidosis, or a non-ketotic hyperglycemic hyperosmolar state(23).

Insulin resistance develops during the surgery and is present for a long time in the postoperative period(23). It can last up to three weeks after the performance of elective surgeries, with greater intensity on the first and second day of the postoperative period(24).

Another biomarker with possible relevance in the metabolic state of surgical patients is interleukin-6 (IL-6), a pro-inflammatory cytokine that mediates the immune response and acts on several cell types. It presents a positive correlation with insulin resistance and is found at high levels in chronic diseases like DM2(23).

One of the selected articles evaluated the effect of the ingestion of preoperative oral carbohydrates on insulin resistance and on the response to surgical stress after lumbar discectomy, using interleukin-6 as marker, verifying that the IL-6 plasma levels increased considerably after 24 hours of skin incision in the group subjected to conventional fasting(11).

A European research study, upon evaluation of the IL-6 levels in 137 patients in the pre- and postoperative periods, verified a high level of IL-6 (≥ 432 pg/mL), as well as a 3 times higher risk of postoperative complications and an increase in hospitalization time. Outcomes such as pneumonia, sepsis, anastomotic dehiscence, wound infection, mortality, and re-surgery were found(25).

Changes in the IGF-1 (insulin-like growth factor) and IGFBP-3 (IGF-1 binding protein 3) serum levels were also detected among patients with preoperative fasting times longer than eight hours. In the postoperative period of abdominal surgeries, 18 patients had a significant reduction in the IGF-I levels and in IGFBP-3 proteolysis, with a consequent increase in insulin resistance(10).

In contrast, patients in shortened fasting had an increase in IGF-I and in IGFBP-3 proteolysis, that is, lower circulating levels of free IGFBP-3 in plasma, indicating that the increased availability of IGF-I and the effects of IGF-I on glucose uptake are involved in the hormone mechanisms for a lower insulin resistance after the surgical trauma(10).

Another study identified a reduction in the IGFB-3 circulating levels by analyzing 80 patients subjected to mastectomy with reduced fasting time and who received a carbohydrate solution two hours before the surgery(26). Despite these findings, there is a scarcity of updated studies addressing the effects of extended preoperative fasting on the IGF-1 and IGBP-3 levels and the consequences of these changes in the postoperative outcome in different medical specialties.

Metabolic effects of extended fasting on the valine and glutamic acid levels were reported in one of the studies included in this review, in which 50 patients in preoperative fasting for more than 16 hours, subjected to gastrointestinal surgery, presented an expressive increase in the plasma concentration of valine and a reduction in the postoperative glutamic acid levels(17).

A possible mechanism that causes the decline in glutamic acid throughout extended fasting is the hepatic catabolism of glutamic acid, intensified in this condition by an increase in the activity of glutamate dehydrogenase, an important enzyme in the hepatic regulation of nitrogen and energy metabolism, catalyzing one of the most relevant anaplerotic reactions(27).

In contrast, the valine levels increased as fasting time advanced, which can be explained by an increase in the degradation of muscle protein to provide the hepatic gluconeogenesis with substrates throughout the fasting period, since valine oxidation is increased in times of inadequate supply of amino acids(17).

No recent reports were found in the literature on the influence of valine and glutamic acid on the postoperative period and its relation with fasting time. Considering the results obtained by the analyzed study(17). The publication of new studies that investigate the influence of preoperative fasting time on the valine and the glutamic acid levels, as well as the metabolic impact on the postoperative recovery, becomes relevant.

2. Relation of the postoperative metabolic changes with preoperative fasting time

Extended preoperative fasting enhances the metabolic response to the surgical trauma(4). The American Society of Anesthesiologists (ASA) recommends the conducts established by the ERAS and ACERTO multimodal protocols, anticipating fasting by ingesting clear liquids up to two hours and light meals up to six hours for healthy patients before elective surgical procedures that need general/local anesthesia or sedation/analgesia(28).

The ten articles reviewed addressed fasting time in their studies, in which six used the case-control method to compare which results were more beneficial to the patient(9-14). These are studies coming from different nations, which demonstrates that the shortening of preoperative fasting is still little practiced, even with the advent of studies that prove its effectiveness.

In the case-control studies that compared patients in traditional fasting (more than 8 hours) to patients in shortened fasting (six hours for solids and two hours for liquids), it was possible to note that the fasting time reflects the reality of many hospital institutions, where the relation between time and the fasting prescribed and practiced is disproportionate(29). In these articles, it was evidenced that fasting with a mean of two hours for clear fluids, including carbohydrate-rich beverages, reduced the postoperative metabolic changes(9-14).

In fact, the reduction in fasting time promotes a safer and more beneficial postoperative period to the patients. When observing the implementation of the ERAS protocols to hepatic surgery in a Brazilian tertiary care center, in the group of patients subjected to ERAS, a reduction in preoperative fasting time was observed (six hours for solids and two hours for liquids) and, consequently, a two-day reduction in the postoperative hospitalization time(30).

The fasting time recommended by the studies was at least eight hours for food and liquid. In Brazil, when evaluating the clinical, surgical, and nutritional profile of 140 surgical patients admitted in a reference hospital, the median of the preoperative fasting time obtained for minor surgeries was 15 hours, while for medium-complexity surgeries was 13.5 hours, which demonstrates non-conformity with the new guidelines. The study also found that malnourished patients presented longer pre- and postoperative fasting and hospitalization time when compared to those well-nourished(31).

In Argentina, the fasting time established by institutions also surpasses the recommendations of the current guidelines. In a study with 139 patients, the mean of the preoperative fasting time prescribed was 12.5 hours, both for solids and liquids, while the actual fasting had a mean of 14 hours for solid food, being longer than prescribed. In comparison to the recommendation of the AAARBA (Asociación de Anestesia, Analgesia y Reanimación de Buenos Aires) guidelines, prescribed fasting exceeded the 4.5-hour recommendation for solids and 10.5 for liquids, not fitting into the current recommendations(32).

One of the articles selected, published in Germany, reports the length of preoperative fasting for a mean time that varied between 16 and 20 hours(16). Another study from Turkey compared the time of the day in which the surgery was carried out to the effect of fasting time on an elective surgery. The fasting means were 12 ± 2.8 and 9.5 ± 2.1 hours in the morning group and 15.5 ± 3.4 and 12.7 ± 4.4 in the afternoon group for solids and liquids, respectively. The greatest changes occurred in the group with longer fasting time(16).

Therefore, preoperative fasting time has a direct relation proportional to the occurrence of postoperative metabolic changes. Shortening preoperative fasting minimizes postoperative metabolic changes, promoting greater comfort and less organic stress to the patient, as well as a reduction in hospitalization time and morbidity(15,16,24).

This study has as a limitation the time frame of publications within the last five years, which made it impossible to select some articles found. The expansion of Brazilian studies on this study object is recommended.

CONCLUSION

The main metabolic changes found were hyperglycemia, increase in the IL-6, cortisol, and valine levels, increase in insulin resistance, reduction in the glutamic acid plasma levels and increase in the IGF-1 levels with a reduction of IGFBP-3.

A direct relation was verified between preoperative fasting time and the occurrence of postoperative metabolic changes. The studies show that reducing preoperative fasting time minimizes postoperative metabolic changes, promoting less organic stress to the patient, and a reduction in hospitalization time and morbidity.

The results found in this study corroborate for a reformulation of the care practices for the surgical patient, by reducing preoperative fasting time, providing the patient with greater comfort and well-being, reducing sensations of thirst and hunger, in addition to a safer clinical/metabolic post-surgery outcome.

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Received: 12/20/2020

Revised: 02/24/2021

Approved: 03/18/2021