Ultrasound-guided L5-S1 Placement of Labor Epidural Does not Improve Dermatomal Block in Parturients

Abstract

(Int J Obstet Anesth. 2019;38:52–58) While epidural analgesia is safe, effective and widely used, studies have shown failure rates of 0.9% to 23% for providing sufficient analgesia to women in labor. Sacral sparing is one of the common causes of failure with labor epidural analgesia. Identification of palpable landmarks is usually used to identify lumbar interspace levels during epidural procedures. The intercristal line has commonly been used to locate the L4-L5 interspace. However, this practice may be ineffective in parturients as this landmark is more cephalad in pregnant patients. In addition, studies have reported that the epidural insertion interspace is correctly identified by palpation of landmarks in only 14% to 29% of cases. The use of preprocedural ultrasound had been reported to decrease the number of puncture attempts and catheter manipulations in parturients undergoing neuraxial procedures. It has also been suggested that placement of an epidural at a lower lumbar level might decrease the risk of sacral sparing. This study aimed to investigate the effectiveness of obtaining an adequate sacral dermatomal block when prepuncture ultrasound was used to place an epidural catheter at the L5-S1 interspace, compared with using surface landmarks to place an epidural at the L3-L4 or L2-L3 interspace.