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: Following successful completion of VCUG and a 60 - min recovery period , the patient ' s level of consciousness and vital signs returned to presedation levels .
### Output Text:
Following successful completion of VCUG and a 60 - min recovery period , the patient ' s level of consciousness and vital signs returned to presedation levels . 