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: In the lateral position with operative side down , patients recived 10 mg ( 2mls ) of 0 . 5 % hyperbaric bupivacaine through a 25 - gauge spinal needle .
### Output Text:
In the lateral position with operative side down , patients recived 10 mg ( 2mls ) of 0 . 5 % hyperbaric <span class="chemical">bupivacaine</span> through a 25 - gauge spinal needle . 