Update for nurse anesthetists evidence-based anesthesia: The use of preprocedural ultrasonography during labor to facilitate placement of an epidural catheter.

Placement of an epidural catheter in parturients can be challenging because the anatomic changes of pregnancy may make it difficult to palpate an ideal insertion point or detect loss of resistance. Preprocedural ultrasonography (U/S-P) is reported to facilitate placement of epidural catheters in parturients. U/S-P provides information on the ideal insertion point, angle of needle insertion, and estimated depth to the epidural space. The purposes of this course are to describe the technique, systematically review the literature, and discuss techniques for integrating U/S-P into practice. It provides evidence demonstrating that U/S-P is a useful adjunct for placement of epidural catheters in obstetrical patients, especially patients with presumed "difficult backs" or obesity.