Usefulness of the Tsui Test in Combined Spinal-Epidural Analgesia in Labour

Combined spinal epidural anesthesia (CSE) is a very effective technique to provide labor analgesia. One of the disadvantages of this technique is the delay in recognizing an error in the position of the epidural catheter because of the effects of the spinal component. Eventually in case of a misplaced catheter, the patient will experience pain or discomfort requiring a repeat procedure after the effect of drug given during the spinal wears off. Low current electrical stimulation test, or the Tsui test, has been used successfully to confirm catheter location in the epidural space. The investigators' objective in this study is to test the usefulness of the Tsui test to confirm the correct placement of the epidural catheter during CSE in laboring patients.