Impact of Epidural Morphine on Shoulder Pain Following Thoracotomy.

This study is designed to assess the impact of epidural morphine on: * The incidence and severity of shoulder pain following a thoracotomy. * The need for additional analgesics, such as opioids for the relief of shoulder pain. * Its safety profile compared to epidural fentanyl following a thoracotomy. The basic hypothesis of this study is that an infusion of epidural bupivacaine and morphine initiated after the induction of anesthesia and continued until 72 hours postoperatively will reduce the incidence and severity of shoulder pain following a thoracotomy when compared to an epidural infusion of bupivacaine and fentanyl.