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: We assessed the effects of ouabain ( 0 . 015 mg / kg body weight ) on hemodynamic , volumetric , and metabolic parameters in 11 patients with severe chronic coronary artery disease without clinical congestive heart failure .
### Output Text:
We assessed the effects of <span class="chemical">ouabain</span> ( 0 . 015 mg / kg body weight ) on hemodynamic , volumetric , and metabolic parameters in 11 patients with severe chronic coronary artery disease without clinical congestive heart failure . 