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 20 deaths , 52 hemorrhagic and thromboembolic complications , and 21 surgical procedures to manage the complications confirm the seriousness of the disorder .
### Output Text:
The 20 deaths , 52 hemorrhagic and thromboembolic complications , and 21 surgical procedures to manage the complications confirm the seriousness of the disorder . 