The introduction of local anesthetics and other medications into the epidural space is a principal technique in provision of anesthesia in many procedures. Typically the anesthetist accesses the epidural space blindly using palpation and visualization of external landmarks and then uses a needle to get to the epidural space. The investigators propose a prospective study of use of ultrasound in a large heterogeneous group of surgical candidates to define the relationship between the actual needle depth (ND) to the epidural space and measured ultrasound depth (UD). Establishing correctly the depth to the epidural space via ultrasound is a component of ultrasound imaging that might improve current technique, and might lead to faster performance of the epidural. Use of ultrasound may also improve the efficacy and safety of epidural placement.