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: Independent predictors of postoperative seizures included age , female sex , redo cardiac surgery , calcification of ascending aorta , congestive heart failure , deep hypothermic circulatory arrest , duration of aortic cross - clamp and tranexamic acid .
### Output Text:
Independent predictors of postoperative seizures included age , female sex , redo cardiac surgery , calcification of ascending aorta , congestive heart failure , deep hypothermic circulatory arrest , duration of aortic cross - clamp and <span class="chemical">tranexamic acid</span> . 