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: CONCLUSIONS : The utilization of phenylephrine to correct hypotension induced by anesthesia has a negative impact on S ( c ) O ( 2 ) while ephedrine maintains frontal lobe oxygenation potentially related to an increase in CO .
### Output Text:
CONCLUSIONS : The utilization of <span class="chemical">phenylephrine</span> to correct hypotension induced by anesthesia has a negative impact on S ( c ) O ( 2 ) while <span class="chemical">ephedrine</span> maintains frontal lobe oxygenation potentially related to an increase in CO . 