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: PATIENTS AND METHODS : We performed a double - blind , randomized controlled trial at an academic medical center of elderly patients ( > or = 65 years ) without preoperative delirium or severe dementia who underwent hip fracture repair under spinal anesthesia with propofol sedation .
### Output Text:
PATIENTS AND METHODS : We performed a double - blind , randomized controlled trial at an academic medical center of elderly patients ( > or = 65 years ) without preoperative delirium or severe dementia who underwent hip fracture repair under spinal anesthesia with <span class="chemical">propofol</span> sedation . 