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 following case is a report of cauda equina syndrome possibly caused by epidural injection of triamcinolone and bupivacaine .
### Output Text:
The following case is a report of cauda equina syndrome possibly caused by epidural injection of <span class="chemical">triamcinolone</span> and <span class="chemical">bupivacaine</span> . 