Loss of Resistance, w/wo Stimulation, For Epidural Placement

All subjects will receive a thoracic epidural catheter placement at the level appropriate for their surgery and will be randomized to either have the epidural placed with a loss of resistance technique alone or loss of resistance technique with confirmation by nerve stimulation. In the traditional loss of resistance technique group, the epidural catheter will be placed after achieving loss of resistance to air. In the electrical stimulation group, following the location of the epidural space with a loss of resistance technique (using air), nerve stimulation will be utilized to elicit a myotomal contraction of the abdominal or thoracic wall. Nerve stimulation will be started at a pulse width of 0.3 ms and a frequency of 1 Hz and a current of 0.2mA.