Anesthesiology Residents: EBM Review and Practice

Provides specialty based search examples for practicing the EBM steps related to asking clinical questions and acquiring evidence.

Clinical Scenario

The Anesthesiology Department has been  developing Enhanced Recovery After Surgery (ERAS) Clinical Pathways for specific surgeries. The pathways provide an evidence based perioperative care plan to guide a consistent approach to each aspect of patient management. The goal is to reduce complications and maximize recovery.

The research evidence for each element of patient care during the preoperative, intraoperative and postoperative period needs to be identified and assessed. Since the evidence base is constantly changing, the evidence will need to be reviewed on a regular basis. Therefore, a "best search" for each topic should be identified and saved so that it can be repeated as needed.

A demonstration search for the following clinical question will be explored in this example:

What effect does preoperative carbohydrate treatment, compared with placebo or preoperative fasting, have on postoperative recovery in adult patients undergoing surgery?

PICOTT Analysis of the Clinical Question

Patient / Problem Adult patient undergoing surgery
Intervention Preoperative carbohydrate
Comparison Placebo OR preoperative fasting
Outcome Postoperative recovery
Type of Question Therapy
Type of Study Systematic Review of RCTs > individual RCTs > cohort studies

PICOTT to Search

Select words from the PICOTT concepts to guide the development of a PubMed search. Remember:

  • Start with key concepts. You do not need to use all of the concepts or all the words.
  • Gender and specific age filters are usually added after a preliminary search unless they are central to the clinical question.
  • Consider alternate word formats and endings, especially for key concepts.
  • Consider synonyms.
  • Use an OR to combine alternate word endings, formats, synonyms. Enclose the set of related words in parentheses.
Question Search Terms
Adult patient undergoing surgery No search terms. The intervention includes the word preoperative and we do not need to duplicate this concept by also searching surgery.
Preoperative carbohydrate

(Preoperative OR Pre-operative) AND (Carbohydrate OR Carbohydrates)

Placebo OR preoperative fasting

No search terms. We are open to no comparison.
Note: Many clinical questions do not include a specific comparison.

Postoperative recovery (Postoperative OR Post-operative)
Study design filters Systematic Review of RCTs > individual RCTs > cohort studies


Preliminary search:
(Preoperative OR Pre-operative) AND (Carbohydrate OR Carbohydrates) AND (Postoperative OR Post-operative)

Evaluate the Search

Run the search in PubMed:

  • On 11/8/2018, this search found 3924 results.
  • Use Customize under Article Types to select Systematic Reviews. This selection limits results to 88, several of which are directly relevant.
  • But why are there so many that do not seem relevant? Some that do not even seem to include the word Carbohydrate? For example:
    Li GH, Hou DJ, Fu HD, Guo JY, Guo XB, Gong H. A review of prophylactic antibiotics use in plastic surgery in China and a systematic review. Int J Surg. 2014 Dec;12(12):1300-5. doi: 10.1016/j.ijsu.2014.10.029. Epub 2014 Oct 31. Review. PubMed PMID: 25448649

Check the Search Details (scroll down the right hand side, click See More):

(Preoperative[All Fields] OR Pre-operative[All Fields]) AND (("carbohydrates"[MeSH Terms] OR "carbohydrates"[All Fields] OR "carbohydrate"[All Fields]) OR ("carbohydrates"[MeSH Terms] OR "carbohydrates"[All Fields])) AND (("postoperative period"[MeSH Terms] OR ("postoperative"[All Fields] AND "period"[All Fields]) OR "postoperative period"[All Fields] OR "postoperative"[All Fields]) OR ("postoperative period"[MeSH Terms] OR ("postoperative"[All Fields] AND "period"[All Fields]) OR "postoperative period"[All Fields] OR ("post"[All Fields] AND "operative"[All Fields]) OR "post operative"[All Fields]))

  • PubMed tries to help your search by mapping terms to Medical Subject Headings (MeSH). If the MeSH term has narrower terms, it will also search all of those. When the MeSH term includes many narrower terms, they can make your search results very noisy. Look at the all Narrower Terms in the MeSH hierarchy for Carbohydrates (scroll down the page). Review: What are MeSH Terms?

Revise the Search

  • The mapping to MeSH for Carbohydrates is not helpful in this search. You can turn off the mapping to MeSH by adding [text word] after Carbohydrate in your search. This will tell PubMed to search only the exact word you enter in the titles, abstracts or MeSH terms.
    (Preoperative OR Pre-operative) AND (Carbohydrate[text word] OR Carbohydrates[text word]) AND (Postoperative OR Post-operative)
  • This search finds 558 results and 25 systematic reviews that seem much more relevant.

Select Articles

Filter Results to Systematic Reviews

The systematic review filter applies a broad search for results that may be true systematic reviews. You need to read the abstracts to identify articles that are about your clinical question and are true systematic reviews. It may be possible to identify higher quality systematic reviews from the abstracts.

The most recent directly relevant high quality systematic reviews in this result set are:

  • Amer MA, Smith MD, Herbison GP, Plank LD, McCall JL. Network meta-analysis of the effect of preoperative carbohydrate loading on recovery after elective surgery. Br J Surg. 2017 Feb;104(3):187-197. doi: 10.1002/bjs.10408. Epub 2016 Dec 21. Review. PubMed PMID: 28000931.
  • Smith MD, McCall J, Plank L, Herbison GP, Soop M, Nygren J. Preoperative carbohydrate treatment for enhancing recovery after elective surgery. Cochrane Database Syst Rev. 2014 Aug 14;8:CD009161. doi: 10.1002/14651858.CD009161.pub2. Review. PubMed PMID: 25121931.

Filter for more recent RCTs

When you find a high quality systematic review you should still look for more recent RCTs. The Amer meta-analysis reports that the last search was conducted in June 2016, so filter the search for RCTs and select any that were published after May 2016. Remember, the default order to display results in PubMed is by publication date.

  • Çakar E. The effect of preoperative oral carbohydrate solution intake on patient comfort: A randomized controlled study. Journal of perianesthesia nursing. 12/2017;32(6):589-599. doi: 10.1016/j.jopan.2016.03.008. PubMed PMID: 29157765.
  • Gomes PC, Caporossi C, Aguilar-Nascimento JE, Silva AM, Araujo VM. Residual gastric volume evaluation with ultrasonography after ingestion of carbohydrate- or carbohydrate plus glutamine-enriched beverages: a randomized, crossover clinical trial with healthy volunteers. Arq Gastroenterol. 2017 Jan-Mar;54(1):33-36. doi: 10.1590/S0004-2803.2017v54n1-06. PubMed PMID: 28079236.
  • Dilmen OK, Yentur E, Tunali Y, Balci H, Bahar M. Does preoperative oral carbohydrate treatment reduce the postoperative surgical stress response in lumbar disc surgery? Clin Neurol Neurosurg. 2017 Feb;153:82-86. doi: 10.1016/j.clineuro.2016.12.016. Epub 2016 Dec 29. PubMed PMID: 28073036.

Critical appraisal

How to appraise an article

Once you have gathered the evidence, you will need to appraise the evidence for its relevance, reliability, validity, and applicability​

Ask questions like:Appraisal Questions

Relevance:  ​
  • Is the research method/study design appropriate for answering the research question?​
  • Are specific inclusion / exclusion criteria used? ​
Reliability:  ​
  • Is the effect size practically relevant? How precise is the estimate of the effect? Were confidence intervals given?  ​
Validity: ​
  • Were there enough subjects in the study to establish that the findings did not occur by chance?    ​
  • Were subjects randomly allocated? Were the groups comparable? If not, could this have introduced bias?  ​
  • Are the measurements/ tools validated by other studies?  ​
  • Could there be confounding factors?   ​
Applicability:  ​
  • Can the results be applied to my organization and my patient?   ​

Use appraisal tools

Worksheets & Checklists
EBM calculators
EBM calculation table
Types of common EBM calculations include:
  • Control Event Rate (CER)
  • Experimental Event Rate (EER)
  • Relative Risk (RR)
  • Relative Risk Reduction (RRR)
  • Absolute Risk Reduction (ARR)
  • Number Needed to Treat (NNT)
  • Confidence Interval (CI)

You can learn how to calculate these manually through the University of Alberta's EBM Toolkit or use Evidence-Based Medicine Toolbox's EBM Calculators & Vanderbilt's Power & Sample Size Calculator