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: Coronary blood flow , cardiac work and metabolism were studied in dogs under sodium nitroprusside ( SNP ) and trimetaphan ( TMP ) deliberate hypotension ( 20 % and 40 % mean pressure decrease from baseline ) .
### Output Text:
Coronary blood flow , cardiac work and metabolism were studied in dogs under <span class="chemical">sodium nitroprusside</span> ( <span class="chemical">SNP</span> ) and <span class="chemical">trimetaphan</span> ( <span class="chemical">TMP</span> ) deliberate hypotension ( 20 % and 40 % mean pressure decrease from baseline ) . 