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© Gland Surgery. All rights reserved. Gland Surg 2022;11(3):563-575 | https://dx.doi.org/10.21037/gs-22-49 Original Article The clinical effect and safety of new preoperative fasting time guidelines for elective surgery: a systematic review and meta-analysis Yuying He1, Rongrong Wang2, Fei Wang1, Lili Chen2, Tingting Shang1, Luya Zheng3 1Operating Room, Taizhou Hospital of Zhejiang Province Affiliated to Wenzhou Medical University, Taizhou, China; 2Nursing Department, Taizhou Hospital of Zhejiang Province Affiliated to Wenzhou Medical University, Taizhou, China; 3Service Center, Taizhou Hospital of Zhejiang Province Affiliated to Wenzhou Medical University, Taizhou, China Contributions: (I) Conception and design: Y He, L Zheng; (II) Administrative support: R Wang; (III) Provision of study materials or patients: F Wang, L Chen, T Shang, L Zheng; (IV) Collection and assembly of data: All authors; (V) Data analysis and interpretation: Y He, R Wang, F Wang, L Chen, T Shang; (VI) Manuscript writing: All authors; (VII) Final approval of manuscript: All authors. Correspondence to: Luya Zheng. Service Center, Taizhou Hospital of Zhejiang Province Affiliated to Wenzhou Medical University, No. 150 Ximen Street, Linhai, Taizhou, China. Email:
[email protected]. Background: Traditional fasting and no drinking schemes (fasting for 8–12 hours and no drinking for 4–6 hours) affect the metabolism of the body. The new guidelines put forward by the American Association of Anesthesiologists (fasting for 6 hours, no drinking for 2 hours) obviously reduce the time of fasting and no drinking, but the clinical efficacy and safety need to be further confirmed. In this study, a meta-analysis of randomized controlled trials (RCTs) using the new guidelines and traditional protocols was conducted to provide an evidence-based foundation for elective surgery. Methods: The articles were searched in PubMed, EBSCO, MEDLINE, Science Direct, Cochrane Library, CNKI, China Biomedical Resources Database, Wanfang Database, Weipu, and Western Biomedical Journal Literature Database. RCTs related to fasting before surgery during the screening period were selected. Chinese and English search keywords included elective surgery, preoperative, fasting and no drinking, patient comfort, thirst, hunger, collapse, hypoglycemia, preoperative gastric volume, preoperative gastric juice pH, and intraoperative gastric volume. The RevMan 5.3 software provided by Cochrane collaboration network was used to evaluate the quality of included documents. Two professionals independently screened the literature, extracted data, and assessed the risk of bias. Results: A total of 6 studies were included. The incidence of hunger in patients undergoing elective surgery in the experimental group and control group was significantly different [Z=3.90; relative risk (RR) =0.58; 95% confidence interval (CI): 0.44, 0.76; P<0.0001]. the="" incidence="" of="" thirst="" was="" significantly="" different="" between="" the="" experimental="" group="" and="" control="" group="" (z="7.22;" rr="0.21;" 95%="" ci:="" 0.13,="" 0.32;=""><0.00001). discussion:="" meta-analysis="" results="" confirmed="" that="" the="" new="" guidelines="" can="" significantly="" reduce="" the="" hunger="" and="" thirst="" of="" patients,="" improve="" their="" satisfaction="" after="" surgery,="" and="" can="" be="" applied="" clinically.="" keywords:="" elective="" surgery;="" new="" guidelines;="" no="" drinking="" and="" fasting;="" clinical="" effect;="" meta-analysis="" submitted="" jan="" 05,="" 2022.="" accepted="" for="" publication="" mar="" 01,="" 2022.="" doi:="" 10.21037/gs-22-49="" view="" this="" article="" at:="" https://dx.doi.org/10.21037/gs-22-49="" 575="" https://crossmark.crossref.org/dialog/?doi="10.21037/gs-22-49" he="" et="" al.="" meta-analysis="" on="" preoperative="" fasting="" time="" in="" new="" guidelines564="" ©="" gland="" surgery.="" all="" rights="" reserved.="" gland="" surg="" 2022;11(3):563-575="" |="" https://dx.doi.org/10.21037/gs-22-49="" introduction="" fasting="" and="" drinking="" before="" elective="" surgery="" is="" to="" reduce="" the="" volume="" and="" acidity="" of="" stomach="" contents,="" prevent="" vomiting="" during="" anesthesia="" and="" aspiration="" pneumonia="" caused="" by="" aspiration="" of="" stomach="" contents,="" so="" long-term="" fasting="" and="" drinking="" before="" surgery="" is="" a="" routine="" clinical="" plan="" (1).="" for="" patients="" undergoing="" nerve="" block="" anesthesia,="" they="" are="" conscious="" after="" anesthesia.="" however,="" once="" nausea="" and="" vomiting="" are="" induced,="" there="" is="" a="" risk="" of="" aspiration.="" for="" patients="" under="" general="" anesthesia,="" the="" risk="" of="" aspiration="" increases.="" therefore,="" it="" is="" necessary="" to="" implement="" fasting="" and="" drinking="" before="" operation="" (2,3).="" at="" present,="" chinese="" textbooks="" still="" hold="" the="" traditional="" view="" as="" to="" the="" time="" of="" water="" fasting:="" adult="" elective="" surgery="" patients="" should="" fast="" for="" 8–12="" hours="" and="" should="" not="" drink="" 4="" hours="" before="" surgery.="" however,="" it="" has="" been="" clinically="" discovered="" in="" recent="" years="" that="" preoperative="" fasting="" time="">10 hours and no drinking time >6 hours can cause adverse reactions such as thirst, hunger, anxiety, dehydration, and hypoglycemia in patients (4-6). Therefore, the American Society of Anesthesiology (ASA) and Enhanced Recovery After Surgery (ERAS) revised the preoperative fasting guidelines in 1999 and 2012, respectively, to shorten the preoperative fasting and no drinking time (7). The new index stipulates that patients undergoing elective surgery can consume sugar-free transparent liquids such as tea, water, and juice 2 hours before surgery. Patients can also eat easily digestible foods such as milk and bread 6 hours before surgery, and can eat normally 8 hours before surgery (8-10). Anesthesiologists’ associations in many countries recommend that patients who undergo elective/limited operation can take appropriate amount of clear fluid orally 2 hours before operation. Some medical units in China also try to put this fasting scheme into practice, but the current situation of clinical application lacks evidence-based basis. Systematic evaluation and meta-analysis are the most commonly used research methods in evidence-based medicine and are the best source of scientific evidence (11). Meta-analysis is a statistical method that combines multiple similar studies with different results from a systematic review into a quantitative indicator (12-14). A systematic review is a comprehensive collection of all relevant studies worldwide, with strict evaluation of all included studies one by one, combined analysis and evaluation of all research results, and meta-analysis when necessary. This is performed to draw a comprehensive conclusion and approach the real scientific evidence, while minimizing bias as much as possible (15-18). The innovation of this study lies in the meta-analysis of RCTs by Cochrane systematic evaluation method through comprehensive retrieval of related studies, aiming to prove that the new guideline scheme can reduce the hunger and thirst of patients, shorten the clinical effect and safety of fasting time in clinical work, and provide sufficient evidence for clinical practice. We present the following article in accordance with the PRISMA reporting checklist (available at https://gs.amegroups.com/article/ view/10.21037/gs-22-49/rc). Methods Article retrieval Articles were searched in PubMed, EBSCO, MEDLINE, Science Direct , Cochrane Library, CNKI, China Biomedical Resources Database, Wanfang Database, Weipu, and Western Biomedical Journal articles database. The articles were RCTs related to fasting and no drinking before elective surgery published from the establishment of the database to May 22, 2021. Journals were manually searched to avoid omissions. The search terms for English databases were “elective surgery”, “preoperative”, “fasting and water deprivation”, and “patients are comfortable”. The Chinese search keywords included “elective surgery”, “preoperative”, “fasting and no drinking”, and “patient comfort”. The search terms on observation indicators for English databases were as follows: thirst, hunger, collapse, hypoglycemia, preoperative gastric volume, preoperative gastric juice pH, and intraoperative gastric volume. The Chinese search keywords were as follows: thirst, hunger, collapse, hypoglycemia, preoperative gastric volume, preoperative gastric fluid pH, postoperative insulin resistance, and intraoperative gastric volume. Search terms and observation index search terms were freely combined to conduct multiple searches and to include more relevant reference articles. Then, search engines were adopted to track each article. Finally, the relevant researchers who published the articles were contacted to obtain the latest research progress. Inclusion and exclusion criteria of the included articles The inclusion criteria of the articles were as follows: articles which were prospective RCTs, limited to Chinese and English only; articles in which the subjects were patients undergoing elective surgery, and the anesthesia method https://gs.amegroups.com/article/view/10.21037/gs-22-49/rc https://gs.amegroups.com/article/view/10.21037/gs-22-49/rc Gland Surgery, Vol 11, No 3 March 2022 565 © Gland Surgery. All rights reserved. Gland Surg 2022;11(3):563-575 | https://dx.doi.org/10.21037/gs-22-49 was general anesthesia; articles in which the intervention measures of the experimental group were preoperative fasting for 6–12 hours and no drinking for 2–3 hours, and articles in which the intervention measures of the control group were traditional fasting for 8–12 hours and no drinking for more than 4 hours; and articles whose outcome indicators included more than one of the following items: thirst, hunger, collapse, hypoglycemia, preoperative gastric volume, preoperative gastric pH, postoperative insulin resistance, and intraoperative gastric volume. The fasting interventions given to the experimental group and the control group were the same, and the key difference between the two was the length of fasting time. Articles meeting the following criteria were excluded: articles which were non-prospective RCTs; articles which were case reports, reviews, conference abstracts, and other non-research articles; articles with children as the research subjects; articles in which the research subjects underwent non-general anesthesia; and articles whose author could not be contacted for the latest data. Clinical outcome indicators The clinical outcome indicators included thirst, hunger, collapse, hypoglycemia, preoperative gastric volume, preoperative gastric pH, intraoperative gastric volume, and postoperative insulin resistance. Data extraction Two professionals were required to use a unified Microsoft Excel spreadsheet (Microsoft, USA) to independently filter articles and extract data, and then cross-checked them. If they encountered differences, it could be resolved through discussion. The main data extracted included: general information of the articles such as title, first author, country, published journal, and publication date; basic information of the research subjects such as gender, age, and sample size; specific operation and follow-up time of intervention measures; extraction of outcome indicators such as thirst, hunger, collapse, hypoglycemia, preoperative gastric volume, preoperative gastric juice pH, postoperative insulin resistance, and intraoperative gastric volume. Evaluation of the risk of bias Two professionals strictly followed the five evaluation criteria of RCTs to repeatedly evaluate the risk of bias of the articles included in the study. If there were any differences, it was resolved through discussion. The evaluation criteria included whether the randomization method was correct; whether allocation concealment was strictly implemented; whether the blinding method was used; whether there was loss to follow-up; whether the number of cases and the age situation were comparable;