| JOURNAL HOME | CME HOME | THIS MONTH | PAST ISSUES | ETOC | COLLECTIONS |
| AUTHORS | REVIEWERS | EDITORIAL BOARD | FEEDBACK | RSS | HELP |
| ||||||||||||||
| ||||||||||||||
|
|
|
|
||||||||||||
|
||||||||||||||
Department of Anesthesiology and Pain Medicine, University of Alberta Hospitals, Edmonton, Alberta, Canada
To the Editor:
We are pleased to read the article by Hayatsu et al. (1) in which they described how electrical stimulation could be used to verify proper placement of an epidural catheter in the epidural space. Evidently, the authors were not aware of our earlier observations on the same topic (2–10). In those clinical reports, we described the successful use of electrical epidural stimulation to confirm epidural catheter placement in the epidural space in both adult and pediatric patients. In our most recent article (3), we demonstrated the practicality of applying this test to guide the placement of a thoracic epidural catheter using the caudal approach in pediatric patients. In that article, we provided a simplified guide to interpret motor responses from electrical stimulation in the event of malplacement of epidural catheters (for instance, subarachnoid, subdural, or intravascular).
From a technical point of view, Hayatsu et al. (1) reported a method using bipolar electrical stimulation that required a specialized catheter, which may limit its application. However, their specialized catheter can provide many other functions, including monitoring of spinal cord potentials, measurement of epidural pressure, and spinal cord stimulation. On the other hand, we described a technique using monopolar electrical stimulation that can be performed with one of the commonly available epidural catheters, which can be readily applied in routine practice.
References
Department of Anesthesiology, Niigata University School of Medicine, Niigata, Japan
In Response:
We appreciate Drs. Tsui and Finucane’s interest in our work (1). We are sorry that we were not aware of their interesting papers.
In earlier works by Shimoji et al. (2–5), they stimulate the spinal cord from the epidural space to produce analgesia and to record the spinal cord potentials using a routinely used epidural catheter with a stainless steel coil inserted through it. They described the bilateral muscle twitch for the midline placement of the epidural catheter electrode (6,7). They also found that the placement of the epidural catheter in the anterior epidural space could be monitored by the waveform of the segmental spinal cord potential (6). Further, the placement of the electrode on the dorsal column (or dorsolateral column) was found to be essential for antidromic activation of interneurons in the caudal part of the spinal segment, as manifested by production of negative and slow positive waves (8). Incidentally, they suggested that spinal cord stimulation with electrodes placed anterior and posterior epidural spaces are more effective in terms of spinal analgesia (5).
We have been routinely using the epidural catheter electrodes that can be used for drug injection, spinal cord stimulation, spinal cord recording, and epidural pressure monitoring, as presented in our previous (9,10) and present (1) articles. Our purpose in this paper was to confirm the accuracy of the placement of the epidural catheter electrode by our back-and-forth maneuvers through a modified Tuohy needle in comparison with the nonmaneuvered control groups.
With regard to the monopolar or bipolar stimulations, the effect of stimulation depends on the site of cathodal electrode, the distance between the cathode and anode, and impedance of the tissue around the electrode (frequently modified by inflammation). Generally speaking, monopolar stimulation causes a diffuse spread of current, which sometimes causes discrepancy between anatomical position and electrical effect in our own experience. However, it may be also true that monopolar stimulation from the epidural space is more effective in terms of analgesic effect than bipolar stimulation with electrodes situated both in posterior and anterior epidural space. However, with regard to electrode positions in the epidural space, and also mono- or bipolar stimulation, it should be studied more in various clinical cases with epidural diseases.
As described above, Shimoji et al. (2–5) used the stainless steel inserted through the epidural catheter about 2 mm beyond the catheter tip for stimulation of the spinal cord as well as recording the spinal cord potentials as described in their earlier works. Advancement of the techniques led to the development of the electrodes as appeared in our present paper (1). These electrodes as described in the recent (1) and our previous papers might widen the clinical application of the techniques rather than limit their application.
References
This article has been cited by other articles:
|
|
 |
|
  B. C. H. Tsui and C. K. C. Sze An In Vitro Comparison of the Electrical Conducting Properties of Multiport Versus Single-Port Epidural Catheters for the Epidural Stimulation Test Anesth. Analg., November 1, 2005; 101(5): 1528 - 1530. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
