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: The haemodynamic effects of adding 15 , 20 or 25 mg of ephedrine to 200 mg of propofol were compared to control in 40 ASA 3 / 4 patients over 60 years presenting for genito - urinary surgery .
### Output Text:
The haemodynamic effects of adding 15 , 20 or 25 mg of <span class="chemical">ephedrine</span> to 200 mg of <span class="chemical">propofol</span> were compared to control in 40 ASA 3 / 4 patients over 60 years presenting for genito - urinary surgery . 