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: None of the patients experienced signs of exaggerated adrenergic response , which was defined as a systolic blood pressure of greater than 200 mm Hg or the occurrence of tachydysrhythmias ( excluding sinus tachycardia ) .
### Output Text:
None of the patients experienced signs of exaggerated adrenergic response , which was defined as a systolic blood pressure of greater than 200 mm Hg or the occurrence of tachydysrhythmias ( excluding sinus tachycardia ) . 