Bupivacaine is a local anesthetic commonly used to manage postoperative pain. Liver resection patients typically have an epidural catheter placed preoperatively through which they receive a continuous infusion of bupivacaine and hydromorphone for up to 5 days postoperatively. The liver metabolizes bupivacaine, and produces proteins that bind with bupivacaine to take it out of circulation and thereby reduce its toxicity. Because a portion of the liver is being removed due to pre-existing liver disease, investigators hypothesize that liver resection patients have an impaired ability to clear bupivacaine from circulation that may increase their susceptibility to bupivacaine toxicity. To assess this, investigators will measure free and bound bupivacaine in liver resection patients postoperatively to determine whether bupivacaine reaches toxic levels. Investigators will also quantify binding protein levels to determine if these levels are reduced after surgery, which could contribute to the elevated bupivacaine levels in these patients. Finally, investigators will monitor patients for signs and symptoms associated with bupivacaine toxicity.