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: METHODS : Newborn piglets received levobupivacaine until cardiovascular collapse occurred .
### Output Text:
METHODS : Newborn piglets received <span class="chemical">levobupivacaine</span> until cardiovascular collapse occurred . 