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: After administration of phenylephrine , MAP increased ( 51 + / - 12 to 81 + / - 13 mmHg ; P < 0 . 001 ; mean + / - SD ) .
### Output Text:
After administration of <span class="chemical">phenylephrine</span> , MAP increased ( 51 + / - 12 to 81 + / - 13 mmHg ; P < 0 . 001 ; mean + / - SD ) . 