• M R Myers.
• Center for Devices and Radiological Health, U.S. F.D.A., Rockville, MD 20852, USA.
• J Biomech. 1996 Feb 1; 29 (2): 139-49.

AbstractThe factors affecting distribution of anesthetic within the spinal column are of current interest due to recent reports of neurological injury occurring during spinal anesthesia. This paper describes a numerical model for simulating anesthetic dispersion, and applies the model to the evaluation of spinal-column size, anesthetic injection rate, and catheter orientation as factors influencing the anesthetic distribution. The model is based upon the finite-element method and incorporates a three-dimensional geometry derived from images of human spinal columns. Simulation results show that the ratio of the cross-sectional dimension of the subarachnoid space within the spinal column to the diameter of the catheter is a critical parameter, with low values of this ratio producing the most uniform anesthetic distributions. Increasing injection rate is found to produce a less uniform distribution in a global sense (higher total volume of anesthetic in the 'sacral' half) but a more uniform distribution in a localized sense (lower concentrations at critical points). Finally, the anesthetic distribution is demonstrated to be highly sensitive to orientation angle at high injection rates.

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