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: These results may suggest that NO is a proconvulsant mediator in lidocaine - induced convulsions .
### Output Text:
These results may suggest that <span class="chemical">NO</span> is a proconvulsant mediator in <span class="chemical">lidocaine</span> - induced convulsions . 