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: Liver transplantation for acutely ill patients with fulminant liver failure carries high intraoperative and immediate postoperative risks .
### Output Text:
Liver transplantation for acutely ill patients with fulminant liver failure carries high intraoperative and immediate postoperative risks . 