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 creatine kinase peaked at 62 , 246 IU / L and the patient was treated with intravenous normal saline .
### Output Text:
The <span class="chemical">creatine</span> kinase peaked at 62 , 246 IU / L and the patient was treated with intravenous normal saline . 