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: We recorded time to first dysrhythmia occurrence , respective times to 25 % and 50 % reduction of the heart rate ( HR ) and mean arterial pressure , and time to asystole and total amount of bupivacaine consumption .
### Output Text:
We recorded time to first dysrhythmia occurrence , respective times to 25 % and 50 % reduction of the heart rate ( HR ) and mean arterial pressure , and time to asystole and total amount of <span class="chemical">bupivacaine</span> consumption . 