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 , a bolus of epinephrine injected through an alternative catheter provoked a hypertensive crisis .
### Output Text:
However , a bolus of <span class="chemical">epinephrine</span> injected through an alternative catheter provoked a hypertensive crisis . 