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: The current sedation protocol progressively increased the rate of successful sedation ( able to complete the imaging study ) when using dexmedetomidine alone from 91 . 8 % to 97 . 6 % ( P = 0 . 009 ) , reducing the requirement for adjuvant pentobarbital in the event of sedation failure with dexmedetomidine alone and decreased the mean recovery time by 10 min ( P < 0 . 001 ) .
### Output Text:
The current sedation protocol progressively increased the rate of successful sedation ( able to complete the imaging study ) when using <span class="chemical">dexmedetomidine</span> alone from 91 . 8 % to 97 . 6 % ( P = 0 . 009 ) , reducing the requirement for adjuvant <span class="chemical">pentobarbital</span> in the event of sedation failure with <span class="chemical">dexmedetomidine</span> alone and decreased the mean recovery time by 10 min ( P < 0 . 001 ) . 