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: Assessing their overall satisfaction , 89 . 7 % would choose propofol anaesthesia again .
### Output Text:
Assessing their overall satisfaction , 89 . 7 % would choose <span class="chemical">propofol</span> anaesthesia again . 