PubMed and CINAHL can be searched for guidelines that were published in journal articles.
PubMed: Run your search, then select "guideline" under "additional filters." You may need to refresh your results to apply the filter after clicking "show."
CINAHL: Run your search, then choose "show more" under "limit to" menu on the left side of the screen. Under "publication type" choose "practice guideline."
Consider also searching sites of professional organizations (for example, the American Academy of Pediatrics) or national non-profit organizations such as the American Heart Associations.