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: An initial dose of 0 . 1 microgram . kg - 1 . min - 1 of PGE1 ( 15 patients ) , or 10 micrograms . kg - 1 . min - 1 of TMP ( 15 patients ) was administered intravenously after the dural opening and the dose was adjusted to maintain the mean arterial blood pressure ( MAP ) at about 60 mmHg .
### Output Text:
An initial dose of 0 . 1 microgram . kg - 1 . min - 1 of <span class="chemical">PGE1</span> ( 15 patients ) , or 10 micrograms . kg - 1 . min - 1 of <span class="chemical">TMP</span> ( 15 patients ) was administered intravenously after the dural opening and the dose was adjusted to maintain the mean arterial blood pressure ( MAP ) at about 60 mmHg . 