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 catheters were changed , and hemodynamics stabilized at lower catecholamine doses .
### Output Text:
The catheters were changed , and hemodynamics stabilized at lower <span class="chemical">catecholamine</span> doses . 