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: After 3 h , these responders randomly received 1 or 2 mg / kg bupivacaine or saline over 5 min , followed by 10 micrograms . kg - 1 . min - 1 epinephrine .
### Output Text:
After 3 h , these responders randomly received 1 or 2 mg / kg <span class="chemical">bupivacaine</span> or saline over 5 min , followed by 10 micrograms . kg - 1 . min - 1 <span class="chemical">epinephrine</span> . 