Response Patterns to the Electric Stimulation of Epidural Catheters in Term Pregnant Women

Lumbar epidural analgesia is commonly used for labor pain relief due to its effectiveness and safety. Despite its very high success rate, the epidural technique remains a rather blind technique and failures continue to occur. The correct placement of an epidural catheter, however, remains a clinical problem, since there is no imaging technique that could be used at the bedside to determine the exact positioning of the catheter. The technique of a trans-catheter electric stimulation test (TCEST) has been successfully used to detect the proper epidural catheter location for pediatric, post-operative and laboring obstetric patients. The response to the TCEST with the uniport (single hole) epidural catheters has been well described. There is a growing body of evidence that multiport epidural catheters provide an advantage to uniport catheters, since additional ports likely allow for an enhanced distribution of the local anesthetic solution. This was shown to result in a lower incidence of inadequate analgesia, including unilateral sensory blockade and missed sensory segments. The characteristics of the TCEST response using a multiport catheter remain to be determined. The aim of this study is to compare the response patterns to the TCEST using a single port versus multiport wire reinforced epidural catheters. The hypothesis of this study is that the incidence of a bilateral response to the TCEST will be higher in the multiport catheter as compared to the uniport catheter.