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: All 24 patients with seizures received high doses of TXA intraoperatively ranging from 61 to 259 mg / kg , had a mean age of 69 . 9 years , and 21 of 24 had undergone open chamber rather than coronary bypass procedures .
### Output Text:
All 24 patients with seizures received high doses of <span class="chemical">TXA</span> intraoperatively ranging from 61 to 259 mg / kg , had a mean age of 69 . 9 years , and 21 of 24 had undergone open chamber rather than coronary bypass procedures . 