Spinal Needle Deflection in the Combined Spinal-Epidural Technique

This is the authors' abstract. We don't add key points for this paper.

In Response: We thank Dr. Eldor for his comments regarding our study [1] and appreciate the opportunity to reply. Dr. Eldor has correctly quoted a sentence from our discussion, however, we are concerned that it has been taken out of context in order to make an unsubstantiated and inaccurate generalization. This part of our discussion addressed clinically relevant solutions to fine-gauge spinal needle deflection from the axis of insertion. We discussed the use of a Tuohy needle as an introducer to reduce needle deflection by tissues ordinarily encountered en route to dural puncture. Additionally, this part of our discussion specifically pertained to fine-gauge Quincke spinal needles (i.e., those with the greatest magnitude of deflection). It would appear to us, and others [2,3], that after a Tuohy needle has been employed to negotiate soft tissue and bony structures in order to successfully locate the epidural space, it can then serve as a useful conduit to guide a fine-gauge spinal needle directly to the dura mater. We believe the popularity of the combined spinal-epidural (CSE) technique is largely the result of the Tuohy needle's reliable facilitation of dural puncture using fine-gauge spinal needles. It is, in contrast to Dr. Eldor's contention, an "ideal" introducer. Dr. Eldor's assertion that the Huber tip of the epidural needle deflects the spinal needle requires qualification. We challenge his assertion that spinal needle deflection through a conventional Tuohy needle is as much as 10 degrees from the axis of insertion. Westbrook et al estimated deflection for the Portex CSE set to be 4-5 degrees [4], which compares favorably with our estimation of the Becton-Dickinson Durasafe CSE set. Furthermore, if the orifice of the Tuohy needle is directed cephalad, it has been postulated that the subsequent oblique puncture of the dura with the Quincke spinal needle may serve to reduce [5] the already low incidence of postdural puncture headache encountered with fine-gauge needles. David R. Uncles, MB,BS, FFARCSI, FRCA Nuffield Department of Anaesthetics John Radcliffe Hospital Oxford, United Kingdom 0X3 9DU B.