Group 1 will receive a single dose of intrathecal morphine (ITM, 4 µcg/kg, or ~0.1-0.3 mg morphine)[10, 12-14] before induction of general anesthesia, followed by postoperative patient-controlled morphine analgesia (IV-PCA) for postoperative pain. Intra-operatively, hemodynamic changes indicative of pain will be treated with intravenous remifentanil (see below).