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: However , shortly after the use of intravenous calcium chloride , the refractory hypotension and complete heart block resolved .
### Output Text:
However , shortly after the use of intravenous <span class="chemical">calcium chloride</span> , the refractory hypotension and complete heart block resolved . 