AMSTAR 2 for the Meta-Analysis, RoB 2 for the Trial: Appraising the Strongest Evidence on Preoperative Carbohydrate Drinks and Finding Where Its Weaknesses Lie
[Student Name]
University of Phoenix
DNP/710: Evidence-Based Practice Measurement and Clinical Inquiry
Week 4 Assignment
[Instructor Name]
[Date]
The appraisal is a model written for teaching purposes.
My search yielded nine studies on preoperative carbohydrate drinks. This paper appraises two of the most important with structured tools: the meta-analysis by Awad et al. (2013), which pooled randomized trials, and the trial by Hausel et al. (2001), which measured the comfort outcomes central to my question. Using tools matched to each design keeps the appraisal systematic rather than impressionistic.
Choosing the Tools
Shea et al. (2017) developed AMSTAR 2 to appraise systematic reviews of randomized and nonrandomized studies of health care interventions, updating the original AMSTAR because reviews increasingly include nonrandomized evidence and decision makers need to distinguish high-quality reviews. Sterne et al. (2019) replaced the original Cochrane risk-of-bias approach with RoB 2, which examines each randomized trial across five domains, each rated on a three-level scale that rolls up into an overall verdict for the trial.
The Meta-Analysis
Awad et al. (2013) included 21 randomized trials with 1,685 patients and found no overall difference in length of stay, but a reduction of about one day in patients undergoing major abdominal surgery. Preoperative carbohydrate treatment reduced postoperative insulin resistance and did not change complications. The authors judged the evidence low to moderate in quality because of heterogeneity.
AMSTAR 2 Appraisal
Research question and components: the PICO elements were stated, satisfied. Protocol: no registered protocol was reported, a critical weakness under AMSTAR 2. Study design selection: limited to randomized trials with a reason, satisfied. Search: multiple databases were searched, with reference checking, a partial yes. Duplicate selection and extraction: reported, satisfied. Excluded studies list: not provided, a weakness. Risk of bias assessment: performed, satisfied. Appropriate meta-analytic methods: random-effects models used with heterogeneity reported, satisfied. Consideration of risk of bias in interpretation: partly addressed through the authors' quality judgment. Heterogeneity discussed: yes, with subgroup analysis. Publication bias: assessed with funnel plots, satisfied. Conflicts of interest: reported.
Heterogeneity in Plain Terms
The reviewers reported an I-squared of 60% for length of stay in major abdominal surgery, meaning much of the variation between trials reflected real differences rather than chance. Differences in drinks, doses and surgeries likely explain it.
Overall AMSTAR 2 Rating
With one critical weakness, the lack of a registered protocol, and a noncritical weakness, the missing excluded-studies list, the review rates as low confidence under AMSTAR 2 rules. That does not make it useless; it means its conclusions should be held cautiously and checked against other reviews, such as the Cochrane review found in my search.
The meta-analysis answered a question about hospital days; my question was about thirst at noon, and only the trial measured that.
Relevance of the Meta-Analysis to My Question
Awad et al. (2013) focused on length of stay, insulin resistance and complications, not thirst, hunger or patient comfort. Its main benefit appeared in major abdominal surgery, while most of our patients have shorter orthopedic and general procedures, where no benefit in length of stay was shown. It supports safety, since complications did not increase, but does not directly answer my primary outcomes.
The Trial
The trial by Hausel et al. (2001) compared three preparations before elective surgery and tracked patient discomfort on visual analog scales at several time points. Its central finding for my question was that the carbohydrate drink eased hunger, anxiety and thirst compared with fasting, while gastric contents were not affected.
RoB 2 Appraisal
Randomization process: random allocation was reported, but the method of concealment was not fully described, some concerns. Deviations from intended interventions: the carbohydrate drink and placebo were designed to look alike, reducing performance bias, but the fasting group was open-label, some concerns for comparisons with fasting. Missing outcome data: few patients were lost, low risk. Measurement of the outcome: outcomes were self-reported, and patients in the fasted group knew they were fasting, which could influence their ratings, some concerns. Selection of the reported result: multiple scales were reported without a published protocol, some concerns.
Industry Involvement
The trial used a commercial carbohydrate drink, and some authors had links to its development. AMSTAR 2 asks reviews to report funding sources, and RoB 2 does not assess funding directly, but industry involvement is worth noting. It does not invalidate the findings, but it strengthens the case for weighing independent trials.
Overall RoB 2 Judgment
With some concerns in several domains, the overall judgment is some concerns rather than low risk. The comparison between the carbohydrate drink and placebo is more trustworthy than the comparison with fasting, since blinding was possible only for the first.
What Would Lower the Bias
A trial comparing a carbohydrate drink with an identical-looking placebo drink, with outcome assessors unaware of allocation and a registered protocol listing primary outcomes, would address most of the concerns identified. Some newer trials in my search meet these standards, and I will weigh them more heavily in the synthesis.
Consistency Across the Two Studies
Both studies found no increase in harm from the carbohydrate drink: the trial showed unchanged gastric contents, and the meta-analysis showed no change in complications. Consistency on safety, from studies with different designs and different weaknesses, is reassuring for a change that asks anesthesiologists to relax a long-held rule.
Applicability
The trial enrolled elective surgery patients similar to ours and measured the outcomes I care about most. Its results apply reasonably well to my population, though it was a single-center trial from 2001 and practice has changed since.
Appraising the Cochrane Review Briefly
The Cochrane review by my search's anchor authors fared better on AMSTAR 2, with a published protocol and comprehensive search. Its own risk-of-bias assessment judged the great majority of included trials weak in some respect, chiefly because patients and assessors knew who received the drink when rating subjective outcomes. That finding echoes my RoB 2 judgment of the Hausel trial and suggests that the field as a whole shares this weakness.
Why Structured Tools Matter
Before this course, I would have summarized the meta-analysis as showing benefit and moved on. Working through each AMSTAR 2 domain showed that the review lacked a registered protocol and did not list excluded studies, weaknesses I would not have noticed. Structured tools make appraisal consistent and reveal problems that a quick reading misses.
Summary of the Appraisal
The meta-analysis supports safety and a modest benefit in major surgery but has low confidence under AMSTAR 2 and addresses different outcomes. The trial directly supports reduced thirst, hunger and anxiety, with some concerns about bias from unblinded comparisons and self-reported outcomes. Together, they suggest benefit and no harm, with uncertainty about size.
Conclusion
Structured appraisal with AMSTAR 2 and RoB 2 showed that the strongest evidence on preoperative carbohydrate drinks has real weaknesses: a meta-analysis without a registered protocol and focused on different outcomes, and a trial with some concerns about bias. The evidence still points toward benefit for comfort and no increase in complications, which I will synthesize with the remaining studies next week.
References
Awad, S., Varadhan, K. K., Ljungqvist, O., & Lobo, D. N. (2013). A meta-analysis of randomised controlled trials on preoperative oral carbohydrate treatment in elective surgery. Clinical Nutrition, 32(1), 34-44. https://doi.org/10.1016/j.clnu.2012.10.011
Hausel, J., Nygren, J., Lagerkranser, M., Hellström, P. M., Hammarqvist, F., Almström, C., Lindh, A., Thorell, A., & Ljungqvist, O. (2001). A carbohydrate-rich drink reduces preoperative discomfort in elective surgery patients. Anesthesia and Analgesia, 93(5), 1344-1350. https://doi.org/10.1097/00000539-200111000-00063
Shea, B. J., Reeves, B. C., Wells, G., Thuku, M., Hamel, C., Moran, J., Moher, D., Tugwell, P., Welch, V., Kristjansson, E., & Henry, D. A. (2017). AMSTAR 2: A critical appraisal tool for systematic reviews that include randomised or non-randomised studies of healthcare interventions, or both. BMJ, 358, Article j4008. https://doi.org/10.1136/bmj.j4008
Sterne, J. A. C., Savović, J., Page, M. J., Elbers, R. G., Blencowe, N. S., Boutron, I., Cates, C. J., Cheng, H.-Y., Corbett, M. S., Eldridge, S. M., Emberson, J. R., Hernán, M. A., Hopewell, S., Hróbjartsson, A., Junqueira, D. R., Jüni, P., Kirkham, J. J., Lasserson, T., Li, T., . . . Higgins, J. P. T. (2019). RoB 2: A revised tool for assessing risk of bias in randomised trials. BMJ, 366, Article l4898. https://doi.org/10.1136/bmj.l4898
How this DNP 710 Week 4 example is structured
The DNP/710 Week 4 work usually appraises evidence with structured tools. This paper matches each tool to the study design, applies its domains with reasons and ends with a judgment about how much confidence the evidence deserves for the specific PICOT question. Students search this week as DNP 710 Week 4, DNP710 Wk 4 or DNP/710 Wk 4; all three are the same assignment.
DNP/710 Week 4 questions, answered
What does DNP/710 Week 4 usually ask for?
Many sections ask students to critically appraise evidence for their PICOT question using structured tools and to summarize strengths, weaknesses and applicability.
What is AMSTAR 2?
A critical appraisal tool for systematic reviews that include randomized or nonrandomized studies of health care interventions, with critical domains such as protocol registration, adequacy of the search and consideration of risk of bias.
What does the RoB 2 tool assess?
Risk of bias in randomized trials across five domains: the randomization process, deviations from intended interventions, missing outcome data, measurement of the outcome and selection of the reported result.
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