Needle bevel direction and headache after inadvertent dural puncture

To study the effect of needle bevel direction on the incidence and severity of headache following inadvertent dural puncture occurring during the identification of the epidural space, the authors randomly assigned obstetric anesthesia residents to identify epidural space with the bevel of the epidural needle oriented either parallel or perpendicular to the longitudinal dural fibers. If dural puncture occurred, an observer unaware of the needle bevel direction, daily assessed the presence and severity of any subsequent headache. Of the 1,558 women who received epidural analgesia during this study, 41 women suffered dural puncture, 20 with the needle bevel oriented perpendicular to the longitudinal dural fibers and 21 with the needle bevel inserted parallel to the dural fibers (NS). Fourteen of 20 women in the group in which the needle bevel was perpendicular to dural fibers developed a moderate to severe headache, whereas only five of 21 in the group in which the needle bevel was parallel to dural fibers did so (P less than 0.005). Similarly, we administered a therapeutic blood patch to ten of 20 women in the perpendicular group but to only four of 21 in the parallel group (P less than 0.05). Thus, identifying the epidural space with the needle bevel oriented parallel to the longitudinal dural fibers limits the size of the subsequent dural tear and, therefore, lowers the incidence of headache should dural perforation occur.