Spinal or epidural analgesia? Difference in methods.

We read the paper published in the Journal with great interest on the comparative study of the analgesic role of bupivacaine (S75-R25) and ropivacaine in labor pain control 1. The study gave original information regarding the analgesic effect of the newly mixed solution of bupivacaine containing 75% of the S isomer and 25% of the R isomer and ropivacaine, and the authors declared that these two drugs can provide good conditions for spinal anesthesia with small indices of adverse events. After careful reading of the whole methods of the study, we are confused about the study protocol. In the title and abstract of the paper, the authors used “spinal anesthesia”, at first sight, to indicate that they administered these two drugs into subarachnoid space, but after following reading of the whole paper, we found the authors in fact performed continuous epidural analgesia, but not what they have demonstrated “spinal anesthesia”. Although spinal and epidural anesthesia all belong to regional anesthesia, there are big differences between these two techniques. Spinal anesthesia requires the injection of local anesthetics into subarachnoid space, but into peridural space when epidural anesthesia is performed. All theses two methods produce contrasting effect on anesthesia or analgesia with different mechanisms 2. As declared, the authors used “spinal anesthesia” in their study; this was a big error in definition of these two anesthetic methods. So we really do not know what anesthesia was used in their study. If such reply is not provided, the results of their paper will mislead readers and produce negative effects on the scientific research and clinical practice. Therefore, this paper should be withdrawn.