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: Fentanyl did reduce minor intraoperative movement but had no sevoflurane - sparing effect and increased respiratory depression , hypotension and bradycardia .
### Output Text:
<span class="chemical">Fentanyl</span> did reduce minor intraoperative movement but had no <span class="chemical">sevoflurane</span> - sparing effect and increased respiratory depression , hypotension and bradycardia . 