[The techniques to identify the epidural space do not influence the success rate in combined spinal-epidural...

The hanging-drop (HD) technique has been attributed to a negative epidural pressure induced by making a tent of the dura by the Tuohy needle. We, therefore, hypothesized that the HD technique would result in more successful intrathecal placement of the spinal needle in combined spinal-epidural anesthesia (CSEA) compared with the loss-of-resistance (LR). Seventy patients received CSEA using the needle-through-needle method with a spinal needle extending 9 mm beyond the Tuohy needle. Success rate in obtaining cerebrospinal fluid (CSF) at the first attempt was considerably low; 60% in HD and 57% in LR, which was not significantly different. Failure to obtain CSF after 3 attempts was not significantly different between the two techniques; 26% and 31% in HD and LR, respectively. In conclusion, there was no advantage of the HD technique for obtaining CSF in CESA compared with the LR. It seems that spinal needle length beyond the Tuohy needle should be more than 9 mm.