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 emergency nurse ought to be familiar with some of the cardiovascular consequences of cocaine use .
### Output Text:
The emergency nurse ought to be familiar with some of the cardiovascular consequences of <span class="chemical">cocaine</span> use . 