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DURAL TRAUMA AND CSF LEAK AFTER EPIDURAL NEEDLE PUNCTURE

Department of Anesthesia, University of Toronto, Women's College Campus, Sunnybrook and Women's College Health Sciences Centre, 76 Grenville Street, Toronto, Ontario M5S 1B2

INTRODUCTION

The effect of epidural needle design, angle of puncture and bevel orientation on dural trauma patterns and CSF leak was examined.

METHODS

Following REB approval, human cadaveric lumbar dura mounted on a cylindrical model of the dural sac, was pressurized to 15cm with artificial CSF(left lateral decubitus pressure) and dura punctured with epidural needles, in randomized order. The pressure was then raised to 25cm(labor/semi-sitting pressure) and leak measured over 15minute intervalsx4. A micromanipulator ensured precise needle angle and bevel orientation at the time of puncture. Dural trauma patterns were examined using Scanning Electron Microscopy (SEM). Dura from the same cadaver was used for every comparison. Part1 addressed the effect of gauge/tip design using 6 epidural needles:17GHustead;17GTuohy;18G Special Sprotte; 18G Crawford; and 20GTuohy(10 cadavers). Punctures were made at 90° to the long axis of the dura, bevel parallel, where applicable. Part2: The effect of needle angle (30 vs 90°) was examined for each of 2needle types: 18GTuohy (bevel parallel, 10 cadavers) and the 18G Special Sprotte Needle (6cadavers). Part3: The effect of bevel parallel vs. perpendicular bevel orientation was examined using the 18GTuohy (10 cadavers). Statistical analysis using RMANOVA was blinded with p<0.05 considered significant.

RESULTS

We found a large(3-5 fold) statistically significant reduction in CSF leak/15 minute interval between the 20GTuohy and each of the other needles examined in Part1 (reported as mean gm+SD per 15minutes; 1gm=1ml; p values=comparison with the 20GTuohy) :Hustead (516 ± 319, p=0.002); 18GTuohy (420 ± 191, p=0.002);17G Tuohy (405 ± 209, p=0.002); 18G Special Sprotte (359 ± 208, p=0.016);18G Crawford (356 ± 121, p=0.0001); 20GTuohy (99.5 ± 112).

Part 2:CSF leak: 18GTouhy 30° 401 ± 135 vs 485 ± 215 at 90° (p=0.31). Leak :18G Special Sprotte 30° 408 ± 205 vs 401 ± 208: at 90° (p=0.96). Part3: Leak after puncture with 18G Tuohy bevel perpendicular 367 ± 119,vs 485 ± 216 bevel parallel (p=0.12).

DISCUSSION

SEM showed characteristic dural trauma patterns for each needle type, orientation and angle of puncture. Results suggest statistically significant reduction in CSF leak with a 20G Tuohy needle compared with larger needles. Large reductions in leak were found with the Tuohy at 30° vs 90° (not statistically significant). Angle of puncture made no difference in leak for the Sprotte epidural needle. Large reductions in leak, not achieving statistical significance were found with a perpendicular Tuohy bevel orientation compared to parallel orientation.

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