title: A numerical investigation into factors affecting anesthetic distribution during spinal anesthesia.
abstract: The 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.
authors.affiliation: Center for Devices and Radiological Health, U.S. F.D.A., Rockville, MD 20852, USA.
authors.forename: M R
authors.initials: MR
authors.lastname: Myers
mesh_terms: D000465:Algorithms; D000775:Anesthesia, Spinal / Q000295:instrumentation / Q000379:methods; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000493:pharmacokinetics*; D002404:Catheterization / Q000295:instrumentation; D003198:Computer Simulation; D006801:Humans; D007278:Injections, Spinal / Q000379:methods; D008956:Models, Chemical; D012447:Sacrum / Q000033:anatomy & histology / Q000378:metabolism; D013116:Spinal Cord / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism; D013131:Spine / Q000033:anatomy & histology / Q000378:metabolism; D013346:Subarachnoid Space / Q000033:anatomy & histology / Q000378:metabolism; D016683:Supine Position
chemical_list: D000779:Anesthetics, Local