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: MEASUREMENTS AND MAIN RESULTS : A total of 342 patients ( 105 dexmedetomidine and 237 propofol ) were included in the analysis , with 190 matched ( 95 in each group ) by propensity score .
### Output Text:
MEASUREMENTS AND MAIN RESULTS : A total of 342 patients ( 105 <span class="chemical">dexmedetomidine</span> and 237 <span class="chemical">propofol</span> ) were included in the analysis , with 190 matched ( 95 in each group ) by propensity score . 