Q. I need articles from EBSCO CINAHL on the use beta blockers for critical care patients

The approach is just to type in your two concepts, beta blockers AND critical care patients and select the best results from the list.

Here are some more things to keep in mind:

1. You can limit to full text under the Limit Your Results box. 
2. You can also narrow down by date. If you are a nursing student, you should not use anything older than 5 years
3. You can also use Subject: Major Heading under the Narrow Results by box. Look for the closest fit to your topic and you'll have fewer articles to look through, and they will all be closer to what you want.
4. You can narrow down even more by selecting a specific age group or gender under the Narrow Results by box, if it is relevant to your research.