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: Mean arterial pressure was decreased 30 + / - 8 per cent from control with infusion of fenoldopam ( 3 . 4 + / - 2 . 0 micrograms . kg - 1 . min - 1 ) and 34 + / - 4 per cent with infusion of sodium nitroprusside ( 5 . 9 micrograms . kg - 1 . min - 1 ) ( NS ) .
### Output Text:
Mean arterial pressure was decreased 30 + / - 8 per cent from control with infusion of <span class="chemical">fenoldopam</span> ( 3 . 4 + / - 2 . 0 micrograms . kg - 1 . min - 1 ) and 34 + / - 4 per cent with infusion of <span class="chemical">sodium</span> <span class="chemical">nitroprusside</span> ( 5 . 9 micrograms . kg - 1 . min - 1 ) ( NS ) . 