In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: The aim of this study is to investigate and compare the protective effects of isotonic sodium chloride with sodium bicarbonate infusion and isotonic sodium chloride infusion with diltiazem , a calcium channel blocker , in preventing CIN .
### Output Text:
The aim of this study is to investigate and compare the protective effects of isotonic <span class="chemical">sodium chloride</span> with <span class="chemical">sodium bicarbonate</span> infusion and isotonic <span class="chemical">sodium chloride</span> infusion with <span class="chemical">diltiazem</span> , a <span class="chemical">calcium</span> channel blocker , in preventing CIN . 