Dose-response meta-analysis is being increasingly applied in evidence production and clinical decision. The research method, synthesizing certain dose-specific effects across studies with the same target question by a certain types of weighting schedule to get a mean dose-response effect, is to reflect the dose-response relationship between certain exposure and outcome. Currently, the most popular method for dose-response meta-analysis is based on the classical "two-stage approach", with the advantage that it allows fixed- or random-effect model, according to the amount of heterogeneity in the model. There are two types of random-effect model available for dose-response meta-analysis, that is, the generally model and the coefficient-correlation-adjusted model. In this article, we briefly introduce two models and illustrate how they are applied in Stata software, which is expected to provide theoretical foundation for evidence-based practice.
ObjectiveTo systematically review the efficacy and safety of different non-peros (NPO) times [( trial group: preoperative solid fast, 6 hours; fluid fast 2–3 hours) vs. (control group: preoperative solid fast, 12 hours; fluid fast 4–6 hours)] in elective general anesthesia patients in China.MethodsRandomized controlled trials (RCTs) and quasi-RCT of NPO time in elective general anesthesia patients were searched and retrieved through online databases (PubMed, Cumulative Index to Nursing and Allied Health, Embase, Cochrane Library, China Biology Medicine database, China National Knowledge Internet, VIP, WanFang, SUMsearch, and Google search engine) and related literatures were reviewed up to April 25th, 2018. Two investigators independently screened literatures, extracted data, and evaluated the risk of bias assessment tools for RCT using the Version 5.1.0 of Cochrane Handbook for Systematic Reviews of Interventions. Then, Meta-analysis was performed using RevMan 5.3 software.ResultsA total of 16 RCTs involving 2 722 elective general anesthesia patients (1 372 in the trial group and 1 350 in the control group) were included. The Meta-analysis showed that: the preoperative residual gastric volume [mean difference (MD)=–1.45 mL, 95% confidence interval (CI) (–2.88, –0.01) mL, P=0.05], the incidence of preoperative hypoglycemia [odds ratio (OR)=0.12, 95%CI (0.05, 0.28), P<0.000 01, the incidence of preoperative thirst [OR=0.15, 95%CI (0.11, 0.21), P<0.000 01], the incidence of preoperative hunger [OR=0.13, 95%CI (0.10, 0.18), P<0.000 01], the incidence of preoperative flustered tiredness [OR=0.11, 95%CI (0.07, 0.17), P<0.000 01], and the incidence of preoperative anxiety [OR=0.21, 95%CI (0.12, 0.37), P<0.000 1] in the trial group were significantly lower than those in the control group. There was no statistically significant difference in the intra-operative residual gastric volume between the two groups (P>0.05), and no intra-operative vomiting or aspiration took place in either group. The recovery time of exhaust and defecate of anus [MD=–8.71 hours, 95%CI (–11.43, –6.00) hours, P<0.000 01] in the trial group was significantly shorter than control group, and there was no statistically significant differences in the incidence of postoperative pneumonia, postoperative nausea, postoperative vomiting, or the postoperative thirsty and hungry between the two groups (P>0.05).ConclusionsCurrent evidence shows that, compared with the control group, the trial group could decrease the incidences of preoperative hypoglycemia, thirst, hunger, flustered tiredness and anxiety, and shorten the recovery time of exhaust and defecate of anus for postoperative patients, without increasing incidences of intraoperative or postoperative adverse reactions. Due to the limited quantity and quality of the included studies, the above conclusions still need to be verified by carrying out more large-scale samples and high-quality RCTs studies.