Keys to minimizing the risk of spinal cord trauma during a lumbar approach to thoracic epidural

Excerpt

Thoracic epidurals provide effective analgesia for thoracic or upper abdominal procedures for both adult and pediatric patients; however, using a thoracic approach to place an epidural catheter is not without risk as it requires needle placement immediately posterior to the spinal cord.1-4 Consequently, some clinicians prefer to use a lumbar approach (caudal approach in pediatric cases), or if unsuccessful at a thoracic level, they may thread the epidural catheter cephalad from that point. This issue of the Journal features an interesting study by Gamble et al.5 in which the authors used a porcine model to address the safety of threading an epidural catheter via a lumbar approach. In their study, the authors show that styletted stimulating thoracic epidural catheters can be advanced in a predictable manner to target thoracic myotomes using a lumbar approach. However, damage to the spinal cord was observed in several animals. It is important to point out that, in humans, such perturbing findings are probably limited to high lumbar approaches (i.e., above L2-L3). This is partly because the human adult spinal cord, unlike the porcine model used in the Gamble et al. study, typically ends at approximately the L1-L2 level. Thus, if needle entry occurs either at or below the L2-L3 level, the risk of direct blunt trauma caused by the initial threading of the catheter from the needle tip is minimized. Nevertheless, the results of Gamble et al.’s study clearly show the risks involved when a catheter is advanced directly towards the spinal cord, as in thoracic and high lumbar approaches. Several key factors influence the risk and potential for spinal cord damage during these approaches, including the angle of catheter insertion, catheter stiffness, and applied force. To address this issue, the relationship between these three factors must be considered. …