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 cumulative bupivacaine dose given at those time points was higher in Group P . Plasma bupivacaine levels were significantly lower in Group P than in Group C . Bupivacaine levels in the brain and heart were significantly lower in Group P and Group L than in Group C .
### Output Text:
The cumulative <span class="chemical">bupivacaine</span> dose given at those time points was higher in Group P . Plasma <span class="chemical">bupivacaine</span> levels were significantly lower in Group P than in Group C . <span class="chemical">Bupivacaine</span> levels in the brain and heart were significantly lower in Group P and Group L than in Group C . 