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EPIDURAL NEEDLE LOCATION USING ELECTRICAL STIMULATION IN CHILDREN

Department of Anesthesiology and Pain Medicine, University of Alberta Hospital, 8440-112 Street, Edmonton, Alberta, T6G 2B7

INTRODUCTION

When using electrical stimulation (ES) to confirm epidural catheter location, a 1-10mA current is required to elicit a motor response.¹ In a porcine model, ES was able to identify the location of a needle in the epidural space without using a loss of resistance (LOR) technique.² This study examines the threshold current needed to elicit a motor response with insulated needles in pediatric patients.

METHODS

After IRB approval and consent, direct epidural placement was performed under general anesthesia. An 18 gauge insulated Tuohy needle was inserted until LOR was obtained. A nerve stimulator was then connected to the insulated needle. The output current was increased from zero until a motor response was visible (up to 15mA). An epidural catheter was then inserted via the needle and its final position was confirmed with ES.

RESULTS

Eight patients were studied (1.7 to 16 years old). The threshold currents (mean ± SD) for insulated needles and epidural catheters were 10.00±3.02mA and 4.31±2.63mA, respectively. In one case, the needle was inserted to a depth in which LOR was felt and a stimulated muscle response was obtained at 15 mA. The needle needed to be advanced another 1mm before the catheter could be passed with ease. After the advancement of the needle, the threshold current was decreased to 12 mA.

DISCUSSION

Based on the preliminary results, the threshold current needed to elicit a motor response was significantly higher with insulated needles than with epidural catheters. This may be as a result of the needle tip being further away from the nerve roots compared to the tip of the epidural catheter. ES may serve as an indicator of entry into the epidural space and alleviate some concerns when advancing a needle after LOR to facilitate the passage of a "difficult to thread" epidural catheter. ES is not intended to replace LOR, but rather to be used in conjunction with, to minimize spinal cord injury following epidural catheterization.

REFERENCES

1 Anesth Analg 2001 93:1152–5.[Abstract/Free Full Text]

2 Anesthesiology2002; 96:A723.

This article has been cited by other articles:

				B. C. Tsui, A. M Wagner, K. Cunningham, S. Perry, and S. Desai ELECTRICAL STIMULATION CAN DISTINGUISH EPIDURAL & INTRATHECAL SPACE Can J Anesth, June 1, 2004; 51(suppl_1): A37 - A37. [Full Text] [PDF]

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