Ultrasound Determination of Needle Depth in Epidurals in Adult Patients

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.

The null hypothesis of this study is that ultrasound depth is similar to the needle depth in
adult non parturient patients undergoing lumbar and thoracic epidurals. A parturient in this
case is defined as a female currently near or going through labor.