Epidural analgesia is one of the most effective methods available for the management of acute pain after major surgery, and has consistently been shown to provide better pain relief than parenteral opioid administration. Epidural analgesia will commonly be initiated and managed by an anesthesiologist. If it is to be used after spinal surgery, the surgeon may place the epidural catheter at the end of the operation. Epidural local anesthetics block the sympathetic nervous system. The resultant vasodilatation may unmask hypovolemia, leading to or at least contributing to hypotension, as the normal response to hypovolemia is peripheral vasoconstriction. Epidural opioids can provide good analgesia. However, most of the outcome improvements attributed to epidural analgesia are the result of the sympathetic blockade caused by local anesthetics and cannot be achieved by opioids alone. Nevertheless, combining low doses of opioids with low doses of local anesthetics maintains the benefits of the local anesthetic use and improves analgesia.