NSG/455 Week 2: Database Search Strategy and Levels of Evidence, sample paper

A Documented Search for Saline Versus Heparin Locks in Implanted Ports: Databases, Terms, Limits, and the Level of Each Source Found

[Student Name]

University of Phoenix

NSG/455: Evidence-Based Practice and Statistics

Week 2 Assignment

[Instructor Name]

[Date]

The infusion center is a composite written for a model paper. Search counts shown are illustrative; a search run on another date will return different numbers.

Week 1 ended with a question comparing saline and heparin port locks for adult oncology outpatients, judged by occlusion and bloodstream infection across the months a port stays in place. This paper documents the search for evidence and rates the level of each source retained. A search that cannot be repeated cannot be trusted, so every choice below is written down as if someone else will run it tomorrow.

Databases

Four sources were searched. The Cochrane Library was searched first, because a systematic review, if one exists, summarizes the trial evidence. PubMed, which indexes MEDLINE, was searched for trials and reviews in medicine and oncology. CINAHL was searched for nursing literature, including practice reports and studies conducted by nurses. Finally, the website of the Infusion Nurses Society was checked for current standards of practice.

Search Terms by PICOT Element

Terms were identified for each element of the question.

Population: implanted ports, using the subject heading Vascular Access Devices and keywords such as "implanted port," "totally implantable venous access device," "port-a-cath" and "TIVAD."

Intervention: saline, using the subject heading Sodium Chloride and keywords "saline," "normal saline" and "0.9% sodium chloride."

Comparison: heparin, using the subject heading Heparin and keywords "heparin lock" and "heparinized saline."

Outcome: occlusion and infection, using the subject heading Catheter Obstruction and keywords "occlusion," "patency," "catheter-related bloodstream infection" and "CRBSI."

The outcome terms were used cautiously, because adding them can exclude relevant articles that report outcomes without using those words in the title or abstract.

Boolean Structure and Limits

Synonyms within each element were combined with OR, and elements were combined with AND: (population terms) AND (saline terms) AND (heparin terms). The outcome block was added only in a second, narrower search. Limits were adults, English language and publication from 2005 onward, with a separate check for older landmark trials cited in reviews. No limit on study design was applied at first, so that reviews, trials and guidelines would all appear.

Problems Met and How the Search Was Adjusted

The first run of the search in PubMed returned more than 900 records, most about peripheral intravenous catheters, dialysis catheters and pediatric lines. Three adjustments narrowed it without losing relevant studies. First, the broad subject heading for all catheters was replaced with the more specific heading for vascular access devices combined with port keywords. Second, the saline and heparin blocks were required to appear in the title or abstract, which removed articles that mentioned the solutions only in passing. Third, a NOT operator was tested to exclude "hemodialysis," but it was removed after it excluded a relevant trial that mentioned dialysis patients as an exclusion criterion; instead, dialysis studies were excluded during screening. A librarian at the hospital reviewed the final strategy and suggested adding "port-a-cath" and "Portacath" as spelling variants, which found two additional records. Recording these adjustments explains why the final strategy looks the way it does and prevents another searcher from repeating the same errors.

Results and Screening

In the illustrative search recorded for this paper, the Cochrane Library returned one directly relevant review; PubMed returned 146 results; and CINAHL returned 61 results. After removing duplicates, 173 records were screened by title and abstract. Records were excluded if they studied children only, peripheral intravenous catheters, dialysis catheters or peripherally inserted central catheters only, or did not compare heparin and saline. Twenty-two full texts were reviewed, and nine were retained. The four most important are described below.

Levels of Evidence

Each retained source was rated on the seven-level scale in Melnyk and Fineout-Overholt (2023). Pooled analyses of randomized trials sit at the top as Level I, single randomized trials are Level II, and the levels then step down through nonrandomized controlled studies, cohort and case-control studies, reviews of descriptive or qualitative work and single descriptive or qualitative studies, to expert committee opinion at Level VII.

Level I. The highest-level source is a Cochrane review that pooled randomized trials of heparin versus saline locks for adult central venous catheters (López-Briz et al., 2018). Because its population includes implanted ports along with other central catheters, its applicability to ports alone must be considered in appraisal.

Level II. Goossens et al. (2013), a randomized, open, non-inferiority trial comparing normal saline with diluted heparin to lock non-valved implanted ports in adults with cancer, directly matches the PICOT population and question. Dal Molin et al. (2015), a multicenter randomized trial comparing normal saline with heparin solution to lock implanted ports, adds a second trial in the target population.

Level VII. The Infusion Nurses Society standards of practice (Gorski et al., 2021) are developed by an expert committee and graded by the strength of their supporting evidence. They represent authoritative guidance but rank low as original evidence.

The remaining five sources were smaller trials and observational studies, rated at Levels II and IV, and will be included in the appraisal matrix in Week 4.

Reflections on the Search

Two lessons emerged. First, the Cochrane review's broader population means the two port-specific trials are especially important, even though they rank below the review. Second, searching CINAHL added practice reports from nurses that showed how centers had implemented saline locks, which will help with the practice change even though those reports are low on the hierarchy.

Conclusion

A documented search of the Cochrane Library, PubMed, CINAHL and professional standards, using subject headings and keywords for each PICOT element, Boolean logic and explicit limits and exclusions, identified a Level I systematic review, two Level II randomized trials in patients with implanted ports and a Level VII practice standard. Rating each source's level sets up the appraisal to come, where the question will be not only how strong each source is but how well it fits this infusion center's patients.

References

Dal Molin, A., Clerico, M., Baccini, M., Guerretta, L., Sartorello, B., & Rasero, L. (2015). Normal saline versus heparin solution to lock totally implanted venous access devices: Results from a multicenter randomized trial. European Journal of Oncology Nursing, 19(6), 638-643. https://doi.org/10.1016/j.ejon.2015.04.001

Goossens, G. A., Jerome, M., Janssens, C., Peetermans, W. E., Fieuws, S., Moons, P., Verschakelen, J., Peerlinck, K., Jacquemin, M., & Stas, M. (2013). Comparing normal saline versus diluted heparin to lock non-valved totally implantable venous access devices in cancer patients: A randomised, non-inferiority, open trial. Annals of Oncology, 24(7), 1892-1899. https://doi.org/10.1093/annonc/mdt114

Gorski, L. A., Hadaway, L., Hagle, M. E., Broadhurst, D., Clare, S., Kleidon, T., Meyer, B. M., Nickel, B., Rowley, S., Sharpe, E., & Alexander, M. (2021). Infusion therapy standards of practice, 8th edition. Journal of Infusion Nursing, 44(1S), S1-S224. https://doi.org/10.1097/NAN.0000000000000396

López-Briz, E., Ruiz Garcia, V., Cabello, J. B., Bort-Martí, S., Carbonell Sanchis, R., & Burls, A. (2018). Heparin versus 0.9% sodium chloride locking for prevention of occlusion in central venous catheters in adults. Cochrane Database of Systematic Reviews, 2018(7), Article CD008462. https://doi.org/10.1002/14651858.CD008462.pub3

Melnyk, B. M., & Fineout-Overholt, E. (2023). Evidence-based practice in nursing & healthcare: A guide to best practice (5th ed.). Wolters Kluwer.