The purpose of this study is to evaluate the best pain medication to be infused in the epidural catheter. At CHOP, the medication infused in the epidural catheter following a chest operation in neonates is a local anesthetic (bupivacaine). However, even with this continuous infusion, neonates still require multiple doses of intravenous opioids (i.e. morphine) because of persistent or constant pain. The administration of intravenous opioids in neonates can have many side effects, such as respiratory depression (reduced breathing rate), sedation, urinary retention (inability to pass urine), itching, nausea and vomiting It has been well documented that by adding a small dose of any opioid to a local anesthetic given through an epidural catheter, the feeling of postoperative pain can be significantly improved in older children and in adults. It is not known whether the addition of an opioid to a local anesthetic is beneficial in neonates. In this study, we are comparing the standard local anesthetic (bupivacaine) with a combination of bupivacaine and a small dose of an opioid (fentanyl).