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In Vivo Diffusion-Weighted Magnetic Resonance Microscopy of Rat Spinal Cord: Effect of Ischemia and Intrathecal Hyperbaric 5% Lidocaine
  1. Helene Benveniste, M.D., Ph.D.,
  2. Hui Qui, M.S.,
  3. Laurence W. Hedlund, Ph.D.,
  4. Peter C. Hüttemeier, M.D., Ph.D.,
  5. Susan M. Steele, M.D. and
  6. G. Allan Johnson, Ph.D.
  1. From the Departments of Anesthesiology and Radiology, Duke University Medical Center, Durham, North Carolina.
  1. Reprint requests: Helene Benveniste, M.D., Ph.D., Department of Anesthesiology, Box 3094, Duke University Medical Center, Durham, NC 27710.

Abstract

Background and Objectives. Pathophysiologic mechanisms underlying persistent neurologic deficits after continuous spinal anesthesia using hyperbaric 5% lidocaine are still not well understood. It has been suggested that high-dose intrathecal lidocaine induces irreversible conduction block and even ischemia in white matter tracts by breakdown of the blood-nerve barrier. In this study, we use diffusion-weighted magnetic resonance microscopy to characterize the effect of intrathecal hyperbaric 5% lidocaine in rat spinal cord. The parameter measured with DWM, is an “apparent diffusion coefficient,” (ADC), which can be used to exclude the presence of ischemia.

Methods. Female Fischer CDF rats were used. Group 1 (n = 5) was exposed to ischemia, group 2 (n = 7) was exposed to intrathecal 5% hyperbaric lidocaine, and group 3 (n = 5) was exposed to intrathecal 7.5% glucose. Diffusion-weighted MR images in group 1 were acquired before and after ischemia induced by cardiac arrest and in groups 2 and 3 rats prior to and during perfusion of the spinal catheter with either 5% hyperbaric lidocaine or 7.5% glucose.

Results. Ischemia decreased the ADC by 40% in gray matter and by 30% in white matter of spinal cord. Continuous intrathecal anesthesia with hyperbaric 5% lidocaine did not affect the spinal cord ADC. Further, 7.5% intrathecal glucose had no effect on ADCs in gray or white matter of spinal cord.

Conclusions. Ischemia reduced the ADC in both spinal cord white and gray matter. Hyperbaric 5% lidocaine did not affect the spinal cord ADC during the first 1.5 hours. We suggest that 5% hyperbaric lidocaine does not induce irreversible neurologic deficits by causing spinal cord ischemia.

  • diffusion
  • hyperbaric 5% lidocaine
  • ischemia
  • magnetic resonance microscopy
  • rat
  • spinal catheters.

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Footnotes

  • All work was performed at the Center for In Vivo Microscopy, Duke University Medical Center, Durham, North Carolina, Research was supported by FAER/American Society of Regional Anesthesia Anesthesiology New Investigator Award 1997 to Dr. Benveniste from the Foundation for Anesthesia Education and Research Grant NIH NCRR No. P41 05959. Part of this work was presented at the ASRA 22nd Annual Meeting, April 11, 1997, Atlanta, Georgia.

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