The Journal of Bone and Joint Surgery, Vol 72, Issue 8 1185-1192, Copyright © 1990 by Journal of Bone and Joint Surgery, Inc
Nerve-roots of the cauda equina. The effect of hypotension and acute graded compression on function
SR Garfin, MS Cohen, JB Massie, JJ Abitbol, MR Swenson, RR Myers and BL Rydevik
Division of Orthopaedics and Rehabilitation, University of California, San Diego.
The influence of hypotension on the function of nerve-roots of the cauda
equina under acute graded compression was studied with use of an
established porcine model. In twenty adult miniature pigs, the nerve-roots
of the cauda equina were compressed at pressures of zero (sham), fifty,
100, or 200 millimeters of mercury, and hypotension was induced with sodium
nitroprusside. Compression was maintained for two hours, and a
ninety-minute period of recovery followed. The nerve-roots were monitored
electrophysiologically throughout the experiment. To assess the effect of
compression and hypotension on the function of the nerve-roots, values of
afferent and efferent amplitude and nerve-conduction velocity were compared
with values in twenty adult miniature pigs that had similar graded
compression without hypotension. Hypotension significantly affected
efferent and afferent amplitudes at the end of the compression period; the
effect remained significant at the end of the recovery period. The most
profound effect of hypotension occurred during compression at fifty
millimeters of mercury--a pressure that had no effect on the function of
the nerves in normotensive animals.
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